Exploring Ocean Worlds: Ocean System Science to Support the Search for Life

Principal Investigator

Christopher R German Woods Hole Oceanographic Institution 266 Woods Hole Road Woods Hole, MA 02543

Additional Investigators Exploring Ocean Worlds: Ocean System Science to Support the Search for Life

TABLE OF CONTENTS

1. Executive Summary 1 2. Summary of Personnel and Commitments 4 3. Research Plan 3.1 Goals and Objectives 5 3.2 Expected Significance 7 3.3 Expanding the State of Knowledge 8 3.4 Technical Approach 9 Investigation 1 10 Investigation 2 13 Investigation 3 16 Investigation 4 22 Investigation 5 29 Investigation 6 33 Synthesis 41 4. Science Management 4.1 Project Structure 45 4.2 Roles and Responsibilities: An Integrated Matrix for Interdisciplinary Research 45 4.3 Project Plan, including anticipated Milestones 47 4.4 Within-Project Communication 49 4.5 Cost Analysis 49 5. Data and Sample Management Plan 50 6. References 53 7. Other Institute Objectives 7.1 Community and Collaboration 73 7.2 Training 75 7.3 Engagement and Collaboration with Minority Institutions 75 7.4 Professional Community Development 79 7.5 Innovative and Effective use of Communications 80 8. Relevance 8.1 Mission Relevance 83 8.2 Fundamental Research to meet NASA’s Long-Term Strategic Needs 86 8.3 Synergistic Collaborations 87 9. Facilities and Resources 88 10. Curricula Vitae 92 11. Current and Pending Support 107 12. Letters of Support from Consortium Institutions 130 13. Budget Summary and Details 141 Exploring Ocean Worlds: Ocean System Science to Support the Search for Life

1. Executive Summary Ocean worlds have become a prominent focus of NASA’s Planetary Sciences endeavor, driven largely by their potential to host extant life. In recent years, NASA has selected instruments for the Europa Clipper mission, initiated a new study for a Europa Lander mission, identified Enceladus and Titan as targets of interest in the current New Frontiers mission opportunity, and established the Roadmap to Ocean Worlds strategic planning activity. Astrobiology is prominent in all of these activities and we consider it timely, therefore, to bring together the astrobiology, planetary science, and ocean science communities in a new, collaborative partnership to provide the scientific underpinning and context needed to explore these worlds in an informed, rigorous manner. Anticipating that geophysical and geochemical differences among ocean worlds will lead to a corresponding diversity in both an ocean world’s biological potential (the abundance and productivity of life that it has the capacity to support) and its biosignature potential (the nature and abundance of evidence for life that is manifest), we ask: On which ocean worlds, and with what measurements, will we have the greatest potential to successfully detect the presence of life? We will integrate astrobiology, ocean system, and planetary sciences to pursue this question, guided by two basic principles: (i) both biological potential and biosignature potential are governed by a network of geophysical and (bio)geochemical processes, not just static conditions; (ii) to be of greatest utility, efforts to quantify biological potential and biosignature potential must identify which observable features are most diagnostic of that network of processes. With this basis, our principle objectives are: Objective 1: Quantify the dependence of biological potential and biosignature potential on physical & (bio)geochemical processes. Objective 2: Identify which observable features would be most powerfully diagnostic of the processes that determine biological and biosignature potential. We will address these objectives by constructing a comprehensive theoretical framework, informed and ground-truthed by experimental efforts, that connects the broad spectrum of physical and chemical processes that likely govern material and energy flux within an ocean system, and thereby determine biological and biosignature potential. Because of their high potential to release chemical energy in association with sub-seafloor fluid flow, we will focus exclusively on ocean worlds on which liquid water oceans are in contact with an underlying rocky seafloor. Our approach is designed to provide a predictive framework applicable to all ocean worlds of this type, but will have clear, immediate and direct relevance to two high priority astrobiology targets: Europa and Enceladus.

Throughout our project, theoretical modelers will work synergistically and iteratively with experimentalists to identify key processes and conditions that contribute to the system-wide function and evolution of ocean worlds. The processes active within any ocean are integrated at the system scale, respecting no disciplinary boundaries. Accordingly, we have assembled a team with a diversity of expertise in astrobiology together with leaders in the study of processes across the various interfaces of the Earth-Ocean-Life system. Our team members will work across a network of six Investigations. Each Investigation is inherently interdisciplinary but, as in Earth’s oceans, we predict that it will be at the interfaces among

1 them that our most exciting and original discoveries will be made. An innovative goal for this project, therefore, is to move beyond the modeling and experimental efforts planned for each “compartment” of the system. Rather, we seek to explore the feedbacks and interconnections among those Investigations and integrate them into a coherent whole, through Synthesis Activities conducted across the lifetime of the project. In meeting our objectives, we will establish a template that can be used to evaluate the biological and biosignature potential of any ocean world – whether based on observations already obtained or those yet to be acquired. This work will be challenging. Resolving the intricacies for system predictions that cross interfaces between physical, chemical and biological disciplines will require intense and intimate deliberations among our diverse team members. It is for this reason that we have selected a small but suitably motivated team for this work: commitment to repeatedly step outside of one’s own “comfort space” and be challenged is a requirement. Implicit in this effort will be the development of a new culture at the intersection of astrobiology and ocean science, one which leverages off these and other disciplines to develop its own distinct area of focus.

Project Management and Coordination: The project will be led by PI German (WHOI), an international expert in deep ocean exploration with recognized expertise in leading and managing complex interdisciplinary projects of this magnitude. He will work directly with a four member Executive Committee (ExComm) selected for balance among the Co-Is, who will serve on a rotating (~2y) basis. ExCom will advise the PI via bi-weekly management tag-ups and help coordinate education, outreach, mentoring and data management activities. At WHOI, the PI will be supported by a strong team including expertise in Project Administration and Multimedia IT/Communications. Additionally: Co-I Girguis (Harvard) will serve as liaison for our collaboration with Roxbury Community College, a Boston area minority serving institution and Co-I Hoehler (NASA-Ames) will oversee ingestion of a complete set of our data products into the Astrobiology and Habitability Environmental Database (AHED), also at NASA-Ames.

Effective communication will be key to the success of our collaboration. PI German has pioneered the use of telepresence for remote coordination of research within the ocean science community including recent completion of an NSF multi-divisional program that included collaboration with social scientists to establish best practices for telepresence- enabled collaborations. He will bring that same skill set to bear in this research. Cohesiveness will be ensured through regular meetings of all team members: 90 minute monthly video-conferences and annual 3-day in person meetings, the last of which will be held in the vicinity of the Kennedy Space Center to coincide with the launch of the Europa Clipper mission. We will also be excited to make meaningful use of NAI’s Workshops Without Walls (WWW) as a cornerstone of our project plan, to ensure that our team’s activities remain firmly tethered to those of the wider astrobiology community.

Throughout our planned project-work, Synthesis Activities, both within our team and through engagement with the broader NAI community, will feature prominently. Our first Synthesis Activity, starting at the outset of the project and including the first WWW (#1) will establish a robust, community-validated conceptual model for assessing the biological potential and biosignature potential of ocean worlds. This first of four key Milestones for our project will capture, documents and employ the current State of Knowledge. Milestone 2 will be timed to occur at mid-project so that we can take best advantage of further community

2 consultation (WWW #2) between the first and second phases of our modelling and experimental work. This milestone will also represent the start-point for our quantitative Synthesis Activities. At Milestone 3 (mid-Y5) we will coordinate a final WWW (#3), coincident with completion of all modelling and experimental work, to share the preliminary results and recommendations arising from our work with the wider NAI community. Our fourth and final Milestone will correspond to completion of the project with all objectives met.

Other NAI Objectives: Our program will train five PhD students and six 2-year post-doctoral researchers over the course of the program. In collaboration with Roxbury Community College (a minority serving institution in the Boston area) we will also engage students from under-represented groups in our Investigations via a series of authentic 3-6 month research placements in team- members’ laboratories. Notably, the majority of the early career researchers across all our institutions will be conducting astrobiological research in laboratories that are focused on Earth-based oceanographic research. We believe that this approach will yield a new generation of interdisciplinary research scientists with a deeper appreciation for, and great enthusiasm to be engaged in, astrobiological research. A highlight of our program will be the development of a semester-long on-line class designed primarily for graduate students. “Searching for Life on Ocean Worlds” will be taught during Phase 2 of our proposal, and will build on WHOI’s established Geodynamics Seminar Series, which itself is an integrated program that fosters interdisciplinary research in geo- and life sciences among graduate students, post-doctoral fellows and faculty.

A key ambition for NAI is to grow the astrobiology community. As a team rich in ocean science expertise, we believe that we have much to contribute to the astrobiology community and, equally, much that we can learn and communicate outward to the wider oceanographic community. Importantly, in keeping with the ethos of astrobiology, we have been trained in the pursuit of interdisciplinary research to investigate Earth-Ocean-Life interconnections throughout our professional careers. Significantly, then, this team will engage a new cohort of internationally recognized leaders from across the ocean sciences who are keen to contribute to NASA’s Astrobiology Program and, specifically, the Ocean Worlds initiative. As well as extending the reach and the membership of the astrobiology community, we anticipate that we will contribute new knowledge and capabilities to the NAI community. Indeed, a further ambition for this project is to deepen as well as broaden collaboration within the NAI. In that regard, we are particularly excited about the opportunities that our team will have to bridge between, and build collaboratively with, two CAN7 teams: Rock Powered Life and Icy Worlds. Further, our team members will be well placed to help forge new partnerships with other agencies interested in ocean world exploration – notably NSF’s Division of Ocean Sciences and NOAA’s Office of Ocean Exploration and Research.

This proposal has emerged from our team members’ extensive engagement in Ocean World missions, mission planning, and program planning, which collectively identified a critical need: that astrobiology, planetary sciences, and ocean sciences communities must partner to develop the scientific underpinning that will guide a rigorous and informed program of ocean world exploration. Our guiding question, our research objectives, and the interdisciplinary team assembled to pursue this work are built for this purpose.

We offer ocean system science to support the search for life.

3 2. Summary of Personnel and Commitments

Work Efforts to be funded by this proposal

Commitment (FTE)

Name Role Y1 Y2 Y3 Y4 Y5 Total

Christopher German PI 0.25 0.25 0.25 0.25 0.25 1.25 Donna Blackman Co-I 0.13 0.13 0.08 0.02 0.06 0.42 Andrew Fisher Co-I 0.06 0.06 0.06 0.06 0.06 0.30 Peter Girguis Co-I 0.04 0.04 0.04 0.04 0.04 0.20 Kevin Hand Co-I 0.12 0.14 0.14 0.15 0.13 0.68 Tori Hoehler Co-I 0.10 0.10 0.10 0.10 0.10 0.50 Julie Huber Co-I 0.17 0.17 0.17 0.17 0.17 0.85 John Marshall Co-I 0.04 0.04 0.04 0.04 0.04 0.20 Jeffrey Seewald Co-I 0.17 0.17 0.17 0.17 0.17 0.85 Everett Shock Co-I 0.04 0.04 0.04 0.04 0.04 0.20 Christophe Sotin Co-I 0.10 0.10 0.10 0.10 0.10 0.50 Andreas Thurnherr Co-I 0.08 0.08 0.08 0.08 0.08 0.40 Brandy Toner Co-I 0.04 0.08 0.08 0.08 0.04 0.32 Total funded work effort 1.34 1.40 1.35 1.30 1.28 6.67

Work Efforts proposed, but NOT to be funded by this proposal Commitment (FTE)

Name Role Y1 Y2 Y3 Y4 Y5 Total

Christopher German PI 0.02 0.02 0.02 0.02 0.02 0.10 Donna Blackman Co-I 0.00 0.00 0.00 0.00 0.00 0.00 Andrew Fisher Co-I 0.06 0.06 0.06 0.06 0.06 0.30 Peter Girguis Co-I 0.08 0.08 0.08 0.08 0.13 0.45 Kevin Hand Co-I 0.00 0.00 0.00 0.00 0.00 0.00 Tori Hoehler Co-I 0.00 0.00 0.00 0.00 0.00 0.00 Julie Huber Co-I 0.02 0.02 0.02 0.02 0.02 0.10 John Marshall Co-I 0.08 0.08 0.08 0.08 0.08 0.40 Jeffrey Seewald Co-I 0.04 0.04 0.04 0.04 0.04 0.20 Everett Shock Co-I 0.00 0.00 0.00 0.00 0.00 0.00 Christophe Sotin Co-I 0.00 0.00 0.00 0.00 0.00 0.00 Andreas Thurnherr Co-I 0.02 0.02 0.02 0.02 0.02 0.10 Brandy Toner Co-I 0.08 0.08 0.08 0.08 0.08 0.40 Total unfunded work effort 0.40 0.40 0.40 0.40 0.45 2.05

4 3. Research Plan 3.1 Goal and Objectives Ocean worlds have emerged as a prominent focus of NASA’s Planetary Sciences endeavor, driven largely by their potential to host extant life (e.g. Sherwood et al., 2017). Recently, for example, NASA has selected instruments for the Europa Clipper mission, initiated a new study for a Europa Lander mission, identified Enceladus and Titan as targets of interest in the current New Frontiers mission opportunity, and established the Roadmap to Ocean Worlds strategic planning activity. We consider it timely, therefore, to bring the astrobiology, planetary sciences, and ocean sciences communities together in a new, collaborative partnership that will provide the scientific underpinning and context needed to explore these worlds in an informed and rigorus fashion. In particular, it is likely that diverse ocean worlds will differ markedly in both biological potential (the abundance and productivity of life that they have the capacity to support) and their biosignature potential (the nature and abundance of evidence for life that they could express). Accordingly, it is important to ask:

On which ocean worlds, and with what measurements, will we have the greatest potential to successfully detect the presence of life?

We will integrate astrobiology, ocean system and planetary sciences to pursue this question, guided by two basic principles: (i) both biological potential and biosignature potential are governed by a complex network of processes and not just static conditions; (ii) to be of greatest utility, efforts to quantify biological potential and biosignature potential must identify observable features that serve to constrain that network of processes. With this basis, our two objectives are:

Objective 1: Quantify the dependence of biological potential and biosignature potential on physical & (bio)geochemical processes.

Objective 2: Identify which observable features would be most powerfully diagnostic of the processes that determine biological and biosignature potential.

We will address these objectives by constructing a comprehensive theoretical framework, informed and ground-truthed by experimental efforts, that connects the broad spectrum of physical and chemical processes that could govern the fluxes of material and energy within an ocean system, and thereby determine biological and biosignature potential. An overview of the physical processes to be considered within our project is shown in Fig.3.1. A complementary schematic of the series of 6 research investigations that we will pursue to reach our objectives is shown in Fig.3.2. Each Investigation is inherently interdisciplinary in itself but, as in Earth’s oceans, we predict that it will be at the interfaces between these different sets of Investigations that our most exciting and original discoveries will be made. Because of their high potential to release chemical energy in association with sub-seafloor fluid flow, we will focus exclusively on ocean worlds on which liquid water oceans are in contact with an underlying rocky seafloor. Our approach is designed to provide a predictive framework applicable to all ocean worlds of this type, but will have clear, immediate and direct relevance to two high priority astrobiology targets: Europa and Enceladus.

5 Figure 3.1 Cartoon schematic showing the physical aspects of ocean system science that we will address in our interdisciplinary study of ocean worlds. Note that, by design, our team draws on a wealth of oceanographic expertise to focus on the physical (shown) and (bio)geochemical processes (not shown) that we anticipate may be active within the oceans of any ocean world. We do not focus on processes active in the overlying ice shell, however, because that complementary expertise is already well represented elsewhere within the NAI, in the CAN 7 Icy Worlds team. Radial lines illustrate the range over which our series of interconnected Investigations will operate (Fig.3.2).

Figure 3.2 Organizational diagram. Our project will proceed through a series of 6 interconnected, interdisciplinary Investigations leading to project-wide Synthesis Activities that will assess both the biological potential and the biosignature potential of ocean worlds.

6 3.2 Expected Significance Our overarching goal is to provide scientific underpinning and context for missions that will seek evidence of life among the ocean worlds of the Solar System. Specifically, by quantifying the dependence of biological potential and biosignature potential on underlying geophysical and geochemical processes, we will provide an interpretive framework that enhances the ability to detect evidence for life from spacecraft observations. Our first priority (Synthesis Activity 1, Y1-2) will be to enhance and generalize the interpretive framework through which observations can be used to assess the biological potential and biosignature potential of ocean worlds. The immediate benefit from this work will be an improved qualitative ability to infer the occurrence of processes on ocean worlds that are currently hidden from view but bear on biological potential, using observations made at and above their icy surface. For example, intriguing compositional analyses have been obtained during the Galileo and Cassini missions from the surface of Europa (Hand & Carlson, 2015) and from the ice-rich plumes emitted from Enceladus (Hsu et al., 2015; Waite et al., 2017). Yet for both moons, the true significance of those results, including their implications for processes that govern biological potential, remains ambiguous. The utility of the interpretive framework we develop will also extend to future missions including: Europa Clipper, Europa Lander, and other missions yet to be selected and/or prioritized, through the New Frontiers 4 mission opportunity, for example, and the Roadmap for Ocean Worlds group in which our team is active. Our second priority (Synthesis Activity 2, Y4-5) will be to carry out quantitative assessments of the biological potential and biosignature potential of ocean worlds, using a robust, predictive, theoretical framework. This activity, drawing upon the results of our rigorous theoretical and experimental investigations, will allow us to develop recommendations to NASA that will be of three major types. First, based on instruments already planned for flight – on Europa Clipper, for example - we will identify and prioritize critical measurements, alone or in combination, that will have the greatest capacity to discriminate among alternative models for ocean chemical evolution and associated biological potential. Second, we will identify which new measurement capabilities - either as new measurement targets or as enhanced performance of existing capabilities - justify the highest priority for development by virtue of their ability to assess biological potential and/or detect evidence of life. Third, by identifying key processes that are as yet poorly constrained or understood (e.g., specific manifestations of water-rock interaction), we will establish priorities for future exploration of Earth analog systems that will most strongly enhance the NAI community's ability to interpret observational data from other ocean worlds. This will afford researchers the opportunity to tailor experiments and technologies for future NASA Ocean Worlds missions. Of wider significance, this team will introduce a new cohort of internationally recognized leaders from across the ocean sciences who are keen to contribute to NASA’s Astrobiology Program and, specifically, the Ocean Worlds initiative. This provides a new, immediate, and direct conduit for the field of astrobiology to expand outward into an established network of our nation’s top oceanographic laboratories. Our team cuts across traditional disciplinary boundaries and harbors a wide range of perspectives and experiences including, importantly, a wealth of field-based experience. Consequently, we already share a profound understanding of what is required to migrate from thoughtful hypothesis generation to the implementation of technically complex interdisciplinary field programs in challenging and hostile environments. All oceanographers, by training, consider the specific processes that they study within the broader context of a single coherent ocean system. By design, however, our team has an even greater strength. Our shared experience studying the intricacies of seafloor fluid flow and its impact on ocean biogeochemical cycles has involved even more aggressive pursuit of interdisciplinary ocean research than is typical, even within the ocean sciences.

7 Our team is also deeply committed to providing opportunities to those who are underrepresented among the oceanographic and space sciences. During the course of our program we will train five graduate students and six post-doctoral researchers. Further, in collaboration with Roxbury Community College in Boston, we will provide opportunities for students from a minority serving institution to gain authentic involvement in our research investigations and to develop skills ranging from geophysics to advanced computer modeling techniques to microbiology, through extended placements within our team-members’ laboratories. During Phase 2 of our project we will also build on an established program at the host institution to develop a semester-long graduate student seminar series that can be offered on line: Searching for Life on Ocean Worlds. When combined with this team’s broader expertise in planetary sciences and astrobiology, in field, laboratory, and modeling research, and in partnership with the larger NAI community, our program will provide an opportunity to grow a diverse and more representative next generation of ocean worlds scientists who are equally comfortable pursuing and leading astrobiological, planetary, and oceanographic research.

3.3 Expanding the State of Knowledge Since the turn of the millennium, it has become apparent that Earth is not the only ocean world. Results from Galileo and Cassini have revealed that there are at least five planetary bodies with global-scale aqueous oceans in the outer solar system: Jupiter’s moons Europa, Ganymede, and Callisto and Saturn’s moons Titan and Enceladus. If the definition of ocean worlds is broadened to include liquid oceans that are not necessarily made of water and not necessarily global in extent, then the list of candidate ocean worlds within the Solar System becomes even longer (Nimmo & Pappalardo, 2016). If we factor in the accelerating rate of discovery and characterization of exoplanets orbiting other stars (e.g. Gillon et al., 2017), the distinct possibility arises that ocean worlds may be pervasive across the Universe. These discoveries are of profound importance to the field of astrobiology. Our state of knowledge has moved rapidly, since Voyager, from an expectation that the outer Solar System was populated by barren featureless ice-covered worlds (Morrison, 1982) to recognition that worlds with abundant aqueous oceans might be present (Nimmo & Pappalardo, 2016). In parallel, our approach to exploration for life has become increasingly sophisticated, from simply “following the water” to recognizing the importance of key CHNOPS elements and the need for a source of energy to sustain life, to the concept that longevity may also be required for life to become established (NASA, 2015). In the case of the outer solar system, far from the Sun, increasing attention has been paid to seafloor fluid flow as a driver for life, whether from thermal or tidal forcing, based on our understandings of chemosynthetic ecosystems and the processes that underpin them in Earth’s oceans (e.g. Shock & Canovas, 2010; Amend et al., 2011). In that context, Europa and Enceladus are of specific interest because both are now understood to host global-scale salt-water oceans that are underlain by a rocky seafloor (Pappalardo et al., 2009; Thomas et al., 2016). As such, they provide two contrasting examples of ocean worlds where geochemical reactants that could sustain chemosynthetic ecosystems could be readily available. It follows that Earth analog processes may be most informative when developing search-for-life missions for these types of system. Of course, an important priority throughout this project will be to remain vigilant, recognizing any field-dependent (oceanographic or planetary) biases we may bring to the project and ensuring that they do not cause past experience to unduly narrow the breadth of our approach. Conversely, while Europa and Enceladus do not set limits to the conditions that could exist on ocean worlds with rocky seafloors, they do provide useful test beds where rich data sets exist (data sets that will continue to be enriched by on-going/planned missions), allowing concept development and proofing. More generally, however, we anticipate that the primary outcome this project will be to

8 provide a comprehensive and unifying, quantitative and predictive framework: one that NASA can use as a valuable tool for prioritizing the future exploration of any and all ocean worlds.

3.4 Technical Approach Throughout our project, theoretical modelers will work synergistically and iteratively with experimentalists to identify key processes and conditions that contribute to the system-wide function and evolution of ocean worlds. The processes active within any ocean are integrated at the system scale, respecting no disciplinary boundaries. Consequently, we have assembled a team with a diversity of expertise in astrobiology together with leaders in the study of processes across the various interfaces of the Earth-Ocean-Life system. An innovative goal for this project is to move beyond the modeling and experimental efforts planned for each “compartment” of the system. Rather, we seek to explore the feedbacks and interconnections among those components to arrive at a template that can be used to evaluate the biological potential of any ocean world – whether based on observations already obtained or those yet to be acquired (Fig.3.2). This work will be challenging. Resolving the intricacies for system predictions that cross interfaces between physical, chemical and biological disciplines will require intense and intimate deliberations among our diverse team members. It is for this reason that we have selected a small but suitably motivated team for this work: commitment to repeatedly step outside of one’s own “comfort space” and be challenged is a requirement. Our goal, building out from this core, is to develop a new culture at the intersection of astrobiology and ocean science - an area where both disciplines have critical expertise and impressive accomplishments in their own right, yet still have much to learn from each other. Our interdisciplinary approach recognizes the pervasiveness of the ocean on any ocean world (Fig.3.1). Its reach extends down to the base of the deepest sub-seafloor aquifer and up to the outermost frozen surface, in the case of ice-covered systems such as Europa and Enceladus. In assessing the biological potential of ocean worlds, a key to our approach is to consider any ocean system as an integrated geochemical reactor. A multitude of geochemical reactions can be predicted throughout any ocean world, wherever its ocean water is present - from water-rock reactions beneath the seafloor to fluid-ocean interactions when resultant fluids are exchanged back into the overlying water column and beyond. But geochemical cycling does not happen in isolation. Consideration of which physical processes are viable helps narrow the range of all possible geochemical outcomes and this, in turn, will inform our development of predictions for the biological potential and biosignature potential within and among different ocean worlds. Importantly, a rich array of feedbacks is also to be expected, between solid planetary interiors, oceans, and life. While geochemical cycles will be key to determining the biological potential and biosignature potential of any ocean world, both will also be dependent on physical processes active throughout the ocean and planetary interior. In the remainder of this section, we address each of our interdisciplinary Investigations and close with a detailed description of our synthesis activities to assess ocean world biological and biosynthesis potential. It is important to note, however, that synthesis activities will be undertaken throughout the project. Indeed, we plan for intense synthesis activity to begin from the very outset, including the first of three planned NAI Workshops Without Walls to solicit community input in Y1, to inform everything that follows. A matrix that shows how our team members will be distributed throughout the interconnected investigations that make up our proposed study is shown in Table 4.1. A complementary Project Plan (Table 4.2), provides further detail on how intimately each of our research investigations are interconnected (Fig.3.2) and, further, provides a graphical representation of how the outcomes from different Tasks within each Investigation will be aligned as we meet each of our four project-wide milestones (See: 4. Project Management Plan).

9 In this investigation we seek to understand how the physical structure and processes active within the rocky interior of an ocean world could generate conditions within which sub-seafloor fluid flow could arise (Investigation 2). Because the primary emphasis for this team’s work is on evaluating ocean worlds that could host chemosynthetic ecosystems through water-rock interactions, all analyses will be based on the premise that each world's ocean is bounded below by a rocky interior, with dominantly silicate composition (Kuskov and Konrod, 2005). The interface between the liquid ocean and underlying rock is an ocean floor environment similar to the Earth's seafloor, although major differences exist. This Investigation will employ numerical tools developed for both planetary and (Earth) marine geophysical studies to investigate the physical processes and determine the parameters needed in Investigation 2 to simulate subseafloor fluid flow on ocean worlds, starting with Europa and Enceladus as contrasting “end- member” examples: Europa has the potential for Earth-like tectonics and magmatism arising from convection in a silicate core while Enceladus is predicted to currently exhibit strong tidal heating generated by tidal dissipaton in a small, porous silicate core (Hussman et al., 2015). Key questions we will address include: Under what conditions could there be convection within the rocky interior of an ocean world? If convection occurs, what would the implications be for lateral variability – both for the generation of topographic features (volcanic seamounts, tectonic rifts) at the seabed and in terms of subseafloor fluid circulation pathways?

Task 1-1. Define the parameter space for 1-D and 2-D models. Our first Task will be to define the parameters to be used, including composition, temperature, heat flux, and porosity, for a variety of geophysical models focused on the rocky silicate layer. Generation of geothermal heat that could drive sub-seafloor fluid circulation will be assessed for three primary mechanisms: internal radioactive decay, solid body tides, and exothermic fluid/rock reactions. The magnitude and lateral scale of possible heterogeneity of the rocky interior will also be evaluated. The scope of our work will be to assess the physical nature of the rocky interior for a range of mineral and ice/water/brine compositions and matrix:fill ratios. We will start with 1-D scenarios (Fig.3.3) and progress to cases where the depth distribution of properties varies laterally, using our initial results to determine the subset of parameters for which 2-D structure could develop. The outermost portion of the rocky interior is most likely to be where sub-seafloor fluid circulation could occur so this is the region for which parameter values determined in Task 1-1 will be considered in detail. The depth at the base of this region will vary with pressure (radius, ice/ocean thickness, gravity) and temperature for a given ocean world. To start, ranges of parameters for rocky interiors will be compiled from existing literature (Hussman et al., 2015; Nimmo and Pappalardo, 2016; and refs. therein), including: layer thickness; elemental and mineralogical composition; bulk density and porosity (including the pressure and temperature dependencies of both). Estimates of bulk (effective) material properties will be derived from a combination of grain (mineral) properties, porosities, and pore-filling (fluid/ice) compositions (e.g. McKinnon and Zolensky, 2003; Hand and Chyba, 2007). Heat generation due to radioactive decay, solid body tides, and exothermic fluid-rock reactions will be calculated based on primary composition and bulk properties. Existing observational and theoretical constraints (e.g., planetary inertia, gravity, magnetics, and Earth analogs) on bulk properties and on the increase in pressure with depth will define the parameter space we adopt for Task 1-2 modeling. Some characteristics for the scenario of an ocean world with a porous interior have already been investigated (e.g., Roberts, 2015), but we will assess a broader range of possible parameter space in light of both recent observations and theoretical considerations.

10 The end member case of a chemically homogeneous rocky silicate layer will serve as a starting point for our parameter calculations, beginning with a given type of (variously evolved) chondrite matrix composition and a pore fill of pure H2O or brine. Complexity will be added sequentially, starting with properties that vary smoothly as a function of depth (e.g., decreasing porosity with increasing depth into the rocky interior). Knowledge of property distributions as a function of depth (pressure) within Earth's oceanic lithosphere [crust: Collier and Singh, 1998; Evans, 1994; Becker, 1985; Blackman et al., 2014) and upper mantle (Contreras-Reyes et al., 2007; Naif et al., 2013; Miller and Lizarralde, 2016)] will guide the extent over which variations are specified. Simple calculations will be used to obtain effective medium properties (viscosity, bulk modulus, specific heat, thermal conductivity and expansivity (Turcotte and Schubert, 1982).

Figure 3.3. Illustration of the parameters, tradeoffs and implications for structure and properties that control behavior of an ocean world’s solid interior. A) Trade-off between the density of the silicate portion of an ocean world’s interior with assumed core/ice thickness for various chondrite compositions (H, L, LL, CM - from Kuskov and Konrod, 2005). B) Phase diagram for H2O, that accounts for different ice phases, under a range of pressure-temperature conditions relevant to contrasting ocean worlds. C) Example of predicted heating due to tidal dissipation (solid red line) and radioactive decay (dashed red line), for a specific scenario of a differentiated interior and an outer ice shell (in this example case, for Europa – from Tobie et al., 2003).

Task 1-2. Assess solid interior convection and tidal deformation. Based on the conditions determined in Task 1-1, we will compute tidal forcing (Sotin et al., 2002; 2009; Tobie et al., 2005) and the magnitude of associated ocean floor deformation. This will provide a first indication of the range of seafloor relief that could influence sub-seafloor fluid circulation, and provide constraints for heat generation by tidal deformation. We will assess whether convection of the rocky interior could occur using a 3-D spherical shell numerical method (Běhounková et al. 2010), with material property assumptions corresponding to a subset of the matrix/fill scenarios explored in Task 1-1. In this method, anelastic dissipation of tidal forcing is simulated via an incompressible Maxwell viscoelastic rheology (Tobie et al., 2005; Sotin et al., 2009) and energy lost over each tidal cycle influences the effective viscosity, which is temperature

11 dependent. Convection within the shell is calculated using the Boussinesq approximation for a viscous fluid with infinite Prandtl number, with mass, momentum, and energy conserved (Běhounková et al., 2010). Coupling of the tidal and convection calculations is achieved through mapping of temperature between the respective model discretizations. Anticipated outcomes from this Task will include assessments of: whether stagnant or mobile lid convection could develop; timescales for advection; and the extent, scale, and persistence of lateral variability. Initial simulations will consider primary rock compositions, and later simulations will include scenarios in which the silicates are hydrated or otherwise modified, physically and/or chemically. Four scenarios are envisioned: (i) Rigid lid convection, where gradients in seafloor topography are limited or nonexistent; (ii) Rigid lid convection, with partial melting and associated volcanic activity; Mobile lid convection, for which we will explore both (iii) plate evolution with distance from a rift, and iv) structure in the vicinity of a subduction zone. Scenario (ii) will provide comparison with Io, in terms of tidal heating dissipated in a silicate layer (Sotin et al., 2009) and potential for magmatic activity (Veeder et al., 2012). Scenarios (iii) and (iv) are novel. It has not been determined, previously, whether mobile lid convection is viable for larger ocean worlds such as Europa. First, we will assess the tectonic mode (rigid or mobile lid convection) using the approach described in Moresi and Solomatov (1998) and refined by Lenardic and Crowley (2012) in which the depth dependence of yield strength plays a key role. Both the history of the lithosphere, such as tidal dissipation history related to orbital evolution (Sotin et al., 2009; Lenardic and Crowley, 2012) and alteration of the silicates by water and associated cracking (e.g. Kelemen and Hirth, 2012), may play important roles. This Task will address these influences in the selection of possible present-day physical/chemical parameters. If convection is viable on an ocean world, we will draw on knowledge from Earth systems to frame 2-D modeling, applying ocean world parameter values to calculate lithosphere spatial variation patterned after the Mid-Atlantic Ridge and Mariana Trench, where diverse styles of chemosynthetic ecosystems occur (e.g. Kelley et al., 2001; Meyer et al., 2016; Okumura et al., 2016; Reveillaud et al., 2016).

Task 1-3. Investigate lateral variability. Using the results of our tidal deformation and convection modeling (Task 1-2), we will estimate lateral gradients in seafloor morphology. An end-member case will be obtained assuming vertical forces are balanced locally by ocean floor topography (e.g. Blackman and Forsyth, 1991; Blackman, 1997). Predictions for the 'lid' properties obtained in the convection modeling will guide calculations that include flexural strength in the balance of forces that could generate topography on the seafloor (e.g. Blackman and Forsyth, 1992; Blackman et al., 2008). If partial melting is determined to be possible, we will assess seamount morphologies that could be generated based on the predicted volume of melt production, eruption pressures, and crustal thickness around locally vs. dynamically compensated volcanoes. The Earth system provides useful analogs for these calculations (e.g. Michael et al., 1994; Klingelhöfer et al, 2001), although lower gravity will result in key differences for other ocean worlds. Results of the seafloor deformation simulations will provide a first-order indication of the scale of lateral variability and implications for sub-seafloor fluid circulation systems, feeding directly into Investigation 2. Additional analyses will consider bulk properties of the rocky interior and also how brittle failure might alter seafloor morphology. For example, if mobile lid convection is predicted and subduction zones could develop, fracturing and slumping at the margin of a trench could sharpen lateral gradients and change rock compositions, locally, due to mineral hydration (Massell, 2002; Ranero et al., 2003). Alternatively, if plates diverge, faulting is likely to control the morphology of the rift zone and influence hydrogeologic properties (Blackman et al., 2014), and thus the nature and scale of sub-seafloor fluid circulation (Titarenko and McCaig, 2015), as has been determined at Atlantis Massif, hosts to the Lost City hydrothermal field (Kelley et al., 2001).

12 The primary goal for this Investigation will be to quantify the potential for fluid circulation within the rocky seafloors of ocean worlds. This circulation may be driven by: buoyancy due to heating, particularly in association with seafloor topography (e.g., Fisher et al., 2003; Hutnak et al., 2008); tidal deformation/pumping, including impacts on rock properties (e.g., Wang et al., 1999; Tivey et al., 2002); and/or exothermic reactions (e.g., Kelley et al., 2001; Lowell and Rona, 2002). On Earth, about 8-12 TW (~25%) of heat loss from the planetary interior occurs through sub-seafloor fluid flow. Importantly, however, only a small fraction of this occurs as high temperature (>250°C) hydrothermal activity. This illustrates a natural tension that informs our approach to the potential for habitability and life on other ocean worlds. On Earth, high temperature vent-fluids host the highest concentrations of redox-active chemical species per unit volume (see Investigation 3) but the majority of sub-seafloor fluid flow, by mass, volume and thermal flux, occurs at lower temperatures distant from the direct influences of tectonic plate boundaries (Stein and Stein, 1994; Mottl, 2003). These lower temperature hydrogeologic systems, which are driven primarily by the cooling of the underlying lithosphere, may dominate the planetary scale ocean geochemical budgets for some species (see review by German & Seyfried, 2014; German et al., 2015) and may also occur at a temperature range that is more compatible with a rich variety of known microbial life (Edwards et al., 2012; Orcutt et al., 2015). The global magnitude of this low-temperature circulation (Johnson and Pruis, 2003) is sufficient to recycle the entire volume of Earth's ocean through volcanic crust every 100k-500k yrs, and to exchange the pore fluid in the volcanic ocean crust every 1k-10k yrs – i.e. comparable to the timescale for the meridional overturning circulation within the oceans (Kostov et al., 2014; Romanou et al., 2017). Earth's low-temperature hydrothermal circulation on ridge flanks is facilitated by seamounts, fracture zones, large igneous provinces, and other basement outcrops (Fisher and Wheat, 2010; Fisher et al., 2014). These features provide permeable pathways that bypass much lower permeability sediments (Spinelli et al., 2004), allowing relatively small driving forces (10's to 100's of kPa; Davis and Becker, 2002) to generate massive volumes of flow. Rocky outcrops on the seafloor can Figure 3.4. Cartoon of a "hydrothermal siphon" showing links be connected to form a among planetary heat loss, bathymetry of a planetary interior below a liquid ocean, and hydrothermal circulation on an ocean "hydrothermal siphon" world (modified from Fisher and Wheat, 2010). In this example, (Fig.3.4) based on the cool fluids enter and exit the rocky interior through local basement difference in pressure in highs that penetrate a sediment layer and provide convective rocks at the base of cool and instability that helps to initiate and sustain fluid circulation. warm hydrostats (Hutnak et

13 al., 2008; Winslow et al., 2016). Such flows can turn an ocean world’s lithosphere into a thermal and geochemical reactor. On Earth, such systems may have been sustaining biomes since early in our planet's evolution (Judson, 2017).

Task 2-1. Assess the nature of seafloor fluid flow on ocean worlds. Our first Task within this Investigation will be to complete a thorough literature review and contribute as well to team- wide and community-wide discussions to assemble a catalog of evidence and constraints on potential hydrogeologic flows on ocean worlds. Topics will include planetary properties, driving forces and heat sources, and potential couplings. We will investigate thermally-driven flows and also assess the potential for flows from tidal deformation. With these results, our team will define the parameter space for modeling. Task 2-2. Define the parameter space for subseafloor hydrogeology modeling. This Task will comprise selection of property ranges to be tested with models, and development of a strategic path for evaluating the relative importance of relevant parameters, including: (a) Nature of the rocky interior immediately below the ocean, selected based on results of Investigation 1. Porosity, density, and thermal conductivity may vary significantly within the rocky interiors, including uniform, depth dependent, and heterogeneous distributions. (b) Seafloor topography. Seafloor relief could create hydrodynamic instabilities within a porous system heated from below, including warping of conductive isotherms and penetration of less permeable sediments (if they exist) by igneous rocks. Systems with and without sediment will be considered – sediments could arise from erosion (interactions of topography with deep ocean currents) and/or from chemical precipitation, even in the absence of biogenic fluxes. (c) Heat production, heat flux, and their distributions. Ocean worlds smaller than Earth may have lower radiogenic heat fluxes (Fig.3.3C) based on the decay of long-lived isotopes, but there could be additional heat flux from tidal compliance (e.g., Tyler, 2009; Nimmo et al., 2014; Fig. 3.3C). There could also be heat sources associated with exothermic reactions during subseafloor fluid flows (e.g, Kelley et al., 2001; Früh-Green et al., 2003), reinforcing the sustainability of circulation systems and increasing spatial variability. (d) Variations in driving forces of circulation based on gravity and fluid compositions. Buoyancy driven flows depend on gravity, which is expected to be much lower on many ocean worlds (Hussman et al., 2015). Driving forces also depend on fluid properties and their physical regime, both of which can be sensitive to small differences in P-T conditions. (e) Permeability. The distribution of permeability in the upper ocean crust on Earth is known to vary widely from direct measurements, modeling, and analyses of formation pressure, temperature, and tidal responses (e.g., Becker et al., 1994; Davis et al., 2000; Fisher et al., 2014; Winslow et al., 2016). For modeling of ocean worlds, we will assign a range of permeability values based on those measured and inferred for Earth's crust, which span 8 orders of magnitude.

Task 2-3. Coupled modeling, Phase 1. Simulations of subseafloor fluid circulation on ocean worlds will build on recent achievements (Fig.3.5) using three-dimensional, hydrogeologic models of Earth's ridge-flank systems (Winslow and Fisher, 2015; Winslow et al., 2016). The 3- D model to be used is described elsewhere (see 9. Facilities & Resources). Initial simulations will focus on coupled fluid-heat transport to which geochemical transport and reactions (Investigation 3) will be added during the second phase of the program, after the nature of circulation controls are elucidated, and the range of potential physical conditions is narrowed (Table 4.2). For example, one study of outcrop-to-outcrop geothermal circulation on Earth has shown that there must be a large (10x to 100x) contrast in the transmittance (outcrop area x permeability) of the outcrops in order to sustain a “hydrothermal siphon” (Winslow and Fisher, 2015).

14 Simulation outputs will be assessed to interpret total and specific hydrologic flows, the efficiency of heat extraction (distribution of conductive versus advective heat transport), the role(s) of heterogeneity of properties, and the range of consequent water-rock ratios. We will also explore the distribution of higher vs. lower temperature fluid circulation, which could bound the extent of extreme rock-water reaction Figure 3.5. Fluid flow vectors from three-dimensional fluid-heat simulation vs. creation of habitat of a crustal-scale hydrothermal circulation system on Earth, with water recharging the crust through one seamount, flowing laterally 50 km, then within the rocky exiting the seafloor through another seamount. Left panel is a perspective interior. These results view looking down at the two-outcrop system, with the crustal aquifer can be mapped onto removed for visualization, and 3% of flow vectors plotted with only X-Y parameter space (horizontal flow) components to illustrate dipole geometry. Detailed panels defined on the basis on right show discharging (top) and recharging (bottom) outcrops, with full of independent three-dimensional vector representation, and the aquifer made translucent theoretical and for clarity. This system is driven by lithospheric heating from below, but a observational studies, similar system on an ocean world could be more strongly influenced by to assess the impacts exothermal rock alteration and/or tidal pumping. Modified from Winslow et of coupled fluid-heat- al. (2016) solute flows on rock and ocean properties. Simulations are likely to be especially helpful in identifying primary controls and the properties that exert the greatest influence on sub-seafloor circulation processes.

Task 2-4. Coupled modeling, Phase 2. The outcomes of sub-seafloor fluid circulation and associated geochemical modeling (Investigation 3) during Phase 1 of the project will likely indicate that some initial assumptions need to be revised. For example, high water/rock ratios at elevated temperatures should be associated with significant alteration, and this could lead to a reassessment of physical properties associated with pore filling and permeability loss (Früh- Green et al., 2004). On the other hand, as seen in Earth systems, more rapid convection can lead to significant crustal cooling, limiting the rate of alteration and helping to sustain circulation for millennia (Fisher and Becker, 2000). Ultimately, a key outcome from Investigation 2 will be a determination of a series of seafloor fluid flow physical fluxes, partitioned into different temperature ranges, essential to our assessment of biological potential (see Synthesis section).

15 This investigation will develop geochemical models of water-rock-organic transformations across the broad range of compositions and conditions that may influence chemical cycling and energy flow on ocean worlds, and thereby provide an energetic basis and framework for evaluating biological and biosignature potential. These models will build on the geophysical and hydrogeological contexts provided by Investigations 1 and 2, and inform the conditions and interpretation of experiments conducted in Investigations 4 and 6.

Task 3-1. Assess the diversity of rock compositions. Our ultimate goal for this investigation is to insert geochemical modeling into a larger interconnected modeling effort that extends from fundamental geophysics to biological and biosignature potential. To start, however, we must first assess the full range of compositional variables to be captured in the geochemical calculations. In addition to pressure, temperature, and their changes over the duration of planetary processes, which will be assessed in Investigations 1 and 2, essential inputs for geochemical modeling include compositions of rocks that host fluids and undergo alteration. While the composition of the rocky interiors of ocean worlds, of necessity, remain model dependent (Zolotov & Shock, 2001; Kuskov & Kronron, 2001, 2005; McKinnon & Zolensky, 2003; Hand & Chyba, 2007; Zolotov, 2007; Zolotov & Kargel, 2009; Sohl et al., 2010; Hussman Figure 3.6. Compositional constraints from meteorites et al., 2015; Nimmo & Pappalardo, showing aluminum to silicon ratios vs the wt % of Fe for 2016), we can gather clues for ordinary and carbonaceous chondrites, as well as primitive ocean worlds in the Solar System and differentiated achondrites. Individual representatives of from the record of meteorites various meteorite classes used in preliminary calculations (e.g., Nittler et al., 2004) and are: CM = Murchison, CV = Allende, H = Batsura, L = efforts to define the composition of Moorabie, LL = Olivenza, PAC = Brachina, HOW = Bholghati, EUC = Petersburg, DIO = Y791194. (Data from Nittler et al. asteroids (e.g., Dunn et al., 2013). 2004, and Nittler’s updated database). Thousands of analyses were compiled by Nittler et al. (2004), whose latest database was used to generate Fig.3.6 and to choose a suite of meteorites for preliminary calculations. Updating, expanding, and critiquing these data to generate input for water-rock models will constitute much of the work in this Task, and can begin immediately.

16 Task 3-2. Water-rock alteration models. Predicting the consequences of fluid-rock reactions with theoretical models built on thermodynamic and kinetic data continues to be a major resource for fueling and testing ideas about geochemical processes and, hence, habitability on ocean worlds. We propose to do so at a scale not previously possible. Utilizing the High End Computing (HEC) facility at NASA Ames, we will conduct millions of simultaneous reaction-path calculations using an automated and integrated system of computer codes (EQ3, EQ6, DBCreate, SUPCRT, CHNOSZ – see: 9. Facilities & Resources), to build up vast libraries of predictions that can cover wide ranges of composition, temperature, and pressure. Calculations will be conducted from 0 to 400°C at pressures up to 500 MPa, and will use the thermodynamic data for aqueous species generated by Co-I Shock and members of his research group (Shock et al., 1989, 1997; Sverjensky et al., 1997; Plyasunov and Shock, 2001; Dick et al., 2006; LaRowe & Dick, 2012; Canovas & Shock, 2016). With this methodology, we can immediately use the results of Task 3-1 to generate hypothetical alteration results for thousands of defined meteorite compositions, together with generalized compositions based on the meteorite record. For example, compositions of the representative meteorites shown in Fig.3.6 were used in preliminary models to illustrate the diverse consequences of variable rock composition on the products of water-rock reactions. As shown in Fig.3.7, these consequences can include very large differences in the potential to supply energy for life, here reflected in the 10 order of magnitude range of the potential microbial substrate, H2. This and other fluid parameters strongly depend on the composition of the primary minerals and resulting alteration assemblage, with ordinary chondrites showing the greatest potential for H2 generation and differentiated achondrites enriched in aluminum the lowest. The influence of parent and alteration mineral assemblages on H2 and other fluid constituents is reflected in Earth systems -2 that range in H2 from 10 molal at submarine hydrothermal systems (Shock & Canovas, 2010) to 10-4 molal in continental serpentinizing systems (Canovas et al., 2017). Once prepared, predictive libraries can be mined for combinations of results capable of explaining observations. In effect, this reverses the long-standing, post-observational role of fluid-rock modeling. It also enables solutions to inverse problems, such as identifying multiple possible scenarios that could lead, non-uniquely, to a given set of observations. In the immediate term, this capability will be fundamentally useful for interpreting data from the Cassini and Galileo missions, as well as enhancing the confidence with which we can interpret observations from Europa Clipper and other future missions (see: 8. Relevance). Results from water-rock alteration models will include volume Figure 3.7 Results of reaction-path calculations at 1°C and 50 MPa for changes in mineral the nine meteorite examples identified in Fig.3.6 as functions of the assemblages that will water-to-rock (w:r) mass ratio. Values of pH decrease with increasing w:r, provide feedback to with fluids from alteration of ordinary chondrites, the primitive achondrite Phase 2 hydrogeology and Allende (CV) all being more alkaline by 2 to 3 pH units than the differentiated meteorites and Murchison (CM). Equilibrium abundances of modeling in dissolved H2 span 10 orders of magnitude. They are greatest for the Investigation 2. ordinary chondrites that contain some metallic Fe and lowest for the Similarly, predicted fluid differentiated meteorites, with carbonaceous chondrites in between. compositions will

17 influence the choice of experimental conditions in the geochemical and biological experiments of Investigations 4 and 6.

Task 3-3. Assess the compositional diversity of volatile inventories. While the preliminary results in Fig. 3.7 show that diverse solar system rock compositions can lead to large variations in fluid compositions, pure water is unlikely to accurately represent solar system oceans. Therefore, the goal of this task is to use constraints from icy worlds, as well as comets and aqueously altered meteorites (Mumma & Charnley, 2011; Lee et al., 2012; A’Hearn et al., 2012; Le Guillou & Brearly, 2014; Volmer et al., 2014; Yurimoto et al., 2014; Le Guillou et al., 2015; Fujiya et al., 2015; Dello Russo et al., 2016) to quantify salinities and other ranges of initial fluid compositions. This work can begin immediately. We expect that the organic composition of fluids derived from comets, and considered to be among the sources of volatiles in ocean worlds, will strongly influence geochemical model results. As shown in Fig.3.8, comets contain significant quantities of organic carbon (molar sum of methanol, formaldehyde, methane, ethane, acetylene, HCN) and inorganic carbon (CO + CO2), which can influence the trajectories of rock alteration pathways and result in fluid compositions that may diverge considerably from the pure-water model Figure 3.8 Volatile inventories of comets are results in Task 3-2. We will include remarkably diverse, containing several mol% organic ammonia and other sources of N as and inorganic carbon as shown here, using combined well as H2S and other sources of S in data from A’Hearn et al. (2012) and Della Russo et al. our inventory of cometary volatiles. The (2016). The star indicates the fluid composition product of this task will be new fluid resulting from the water-rock simulation for Murchison models for ocean worlds that will feed (CM) shown in Fig.3.7. All other simulated fluids in into Task 3-4, as well as planned Fig.3.7 plot closer to the H2O apex. experiments (Investigations 4 and 6).

Task 3-4. Water-rock-organic alteration models. Here, we will build on the inventory described in Task 3-3 to model the consequences of reactions between fluids derived from comets and rocks defined by meteorites, and compare the results with those obtained in Task 3- 2, and with planetary data. The star at bottom left in Fig.3.8 indicates the fluid composition resulting from the water-rock model for Murchison, the most carbon-rich meteorite among those shown in Fig.3.7. As indicated in Fig.3.8, comet-derived fluids are likely to be far more enriched in organic and inorganic sources of carbon. Our expectations are that molar abundances of organic solutes such as methanol will have dramatic effects on the pH and redox state during alteration processes, as may aqueous solutions saturated with light hydrocarbons. We will also incorporate new results from an independent project (funded by NASA’s Emerging Worlds program) to evaluate the properties of CO2 as a planetary fluid and evaluate thermodynamic properties of carbonic-fluid solutes. Fluid-rock models are not part of that proposed research, so efforts in this project to incorporate carbonic fluids in geochemical models will be entirely complementary.

18 Task 3-5. Redox disequilibria and biosynthetic potential. Water-rock-organic alteration transforms fluid compositions, and when transformed fluids mix with one another, or back into their source fluids, rapid changes in composition and temperature generate the potential for redox disequilibria that could supply energy for life (McCollom & Shock, 1997; Shock & Schulte, 1998; Amend & Shock, 1998; Shock & Canovas 2010; Amend et al., 2011). In this Task we will quantify and rank the sources of redox disequilibria generated as fluids mix, starting by mixing all fluids resulting from water-rock and water-rock-organic models back into their source fluids.

We have not yet begun to do this for ocean worlds, but we do have ample results from models of submarine venting on Earth to illustrate what we might learn. Fig.3.9 shows results of model calculations that illustrate how rock composition can influence energy supplies for microbes, as determined from a two-step process. In Step 1, we calculate the equilibrium reaction paths for seawater with about 400 mid- ocean ridge basalt (MORB) compositions that represent averages for different ridge segments. In Step 2, non- equilibrium mixing of those hypothetical vent fluids back into Figure 3.9 Energy supplies for autotrophic methanogenesis the original seawater composition evaluated from the disequilibrium for the reaction shown for generates redox disequilibria. Fig fluid compositions obtained by mixing hypothetical 350°C hydrothermal fluids generated from water-rock models for a 3.9 shows conditions at ~83°C, globally distributed MORB dataset back into seawater. corresponding to a seawater-to- Because the aluminum content of the primary MORB vent-fluid mixture of about 3.3 to 1. influences the stability of epidote, which accommodates ferric The energy shown is for iron and facilitates H2 production, the abundance of Al2O3 can autotrophic methanogenesis, as be more influential than the total amount of FeO in indicated by the reaction shown. determining the potential for H2 production and therefore the The results are plotted in a energy return from methanogenesis. reference frame provided by the rock composition - in this case, [Al2O3] and [FeO] in the MORBs. Variations in methanogenic energy yield are driven by the dependence on aqueous H2 activity, and the possibly counterintuitive result that it is not the FeO abundance on its own that determines how much H2 can form. Rather, the abundance of Al2O3 has a strong effect. The reasons for this involve stabilization of chlorite and epidote in the alteration assemblage, which controls the fate of the Fe(II) in the original MORB composition. Thus, the progress of the reaction involving the bulk composition and the mineral reaction products that can form determines the energy content and associated biological potential of resulting fluid mixtures. Waite et al. (2017) presented one example (for the specific case of methanogenesis from H2 and CO2 on Enceladus) of the broad range of calculations to be undertaken here. In this Task, energy supplies for hundreds of redox reactions will be quantified for each of the millions of water-rock and water-rock-organic models from Tasks 3-2 and 3-4.

19 The calculated energies will be equated to biosynthetic yield, as one dimension of biological potential, using the thermodynamic-based parameterization described by Heijnen & van Dijken (1992). The calculations will account for the sensitivity of yields to aerobic vs. anaerobic conditions (Heijnen & van Dijken, 1992; McCollom & Amend, 2005), and will also incorporate, as a tunable variable, a threshold value for molar Gibbs energy change below which redox processes do not contribute toward biosynthesis (Schink, 1997; Hoehler et al. 2001). Particularly for low energy metabolisms (e.g., methanogenesis), imposing this threshold may significantly diminish the energy available for biosynthesis (Hoehler, 2004). Computed biosynthetic yields will represent upper limits on how much biological material can be synthesized in a fluid of specified composition, because they account only for production, not consumption, of biomolecules, and because they assume that all bioavailable energy is partitioned into new growth. In practice, a non-trivial fraction of the energy flux into most natural systems goes to support standing biomass (Tijhuis et al. 1993; van Bodegom, 2007; Hoehler, 2004; Hoehler & Jørgensen, 2013). The Synthesis Activities, by integrating the results of Investigations 1-4, will place upper limits on standing biomass abundance, a second dimension of biological potential. This will allow us to evaluate the influence of variable maintenance vs. growth energy partitioning on overall biosignature potential. Results of the redox disequilibrium/biosynthesis calculations will be assembled into a searchable/operable database that relates fluid composition and biosynthetic potential to the broad range of compositions and reaction conditions identified in Tasks 3-1 and 3-3. This database provides not only the basis for Task 3-6, but also a resource for the broader planetary science and astrobiology communities.

Task 3-6. Compositional proxies for biosynthetic potential. As illustrated in Fig 3.9, the energy made available to specific metabolisms through water-rock reactions is often governed by variations in composition (e.g., the aluminum content of the rocks) and conditions of reaction that cannot be directly observed by spacecraft. However, those same variations may influence the abundance of aqueous products that could conceivably be observed. In this task, we will assess the variance in biosynthetic potential, and its correlation with compositional variables (i.e., potentially observable parameters on future NASA missions), across the database created in Task 3-5. Our strategy for doing so recognizes that the outputs of the reaction path simulations – roughly 240 parameters that characterize the composition of the system (Wolery, 1992) – present both a basis for Figure 3.10 Fluid compositional proxies for biosynthetic computing the energy available in potential. The energy yield data from Fig.3.9 have been oxidation-reduction chemistry (Task 3- converted into biosynthetic yield and replotted against 5) and an associated set of fluid compositional outputs of the reaction path model (vs. compositional data, many of which solid compositional inputs in Fig.3.9). In this example, 2+ + represent potentially observable hypothetical constraints on fluid Ca and K characteristics. In general, we concentration (shaded regions) constrain biosynthetic anticipate that specifying a value or potential to 63% of the full range represented in the plot.

20 range for a given compositional variable will identify a subset of the modeled reaction paths that yield that specific value (Fig.3.10). For example, only a subset of all possible reaction paths will yield a fluid salinity within the range 1 ± 0.1%, and only the range of biosynthetic potential represented within that subset would be consistent with an observed salinity in that range. However, that subset may still represent a large and diverse number of possible reaction paths, corresponding to a large range of biosynthetic potential. Constraining an additional variable – for example, fluids of the indicated salinity that also have a pH with a specific range – may serve to further narrow the subset of compatible reaction paths, and their associated biosynthetic potential. The intent of this task is to systematically explore how the range of modeled biosynthetic potential shrinks as different observational constraints are imposed. In particular, we seek to identify constraints that, individually or in combination, have the potential to narrow that range most rapidly. These would constitute high priority measurements for spacecraft observations. We will conduct these studies in two modes: (a) We will identify the compositional variables that correlate most strongly with biosynthetic potential, using the dataset generated in Task 3-5, and then quantify how precisely each variable specifies biosynthetic potential over a broad range of values. In its most basic form, this will comprise a simple pair-wise correlation analysis, but we will test the utility of principle component analysis and dimensionality reduction techniques in more rapidly identifying the compositional variables that best explain the variance in biosynthetic potential. In order to further reduce the scope of this task, we will initially restrict the analysis to a subset of 20-25 compositional outputs (from among the approximately 240 outputs per reaction path simulation), specifically prioritizing variables that may be amenable to spacecraft observation. The analysis can be expanded to a larger set of compositional variables, should the initial set fail to significantly explain the variance in biosynthetic potential. (b) We will quantify the range of biosynthetic potential that is consistent with existing compositional constraints for the oceans of Enceladus and Europa, making no other assumptions about starting composition or conditions of reaction. For example, constraints have been placed on the sodium chloride content, pH, and other components of Enceladus’ ocean (Postberg et al., 2009; Glein et al., 2015). If we allow for a wide range of initial compositional states and reaction conditions, to what extent do these compositional indicators constrain biosynthetic potential? The results provide a basis for numerical experimentation in three ways. First, we will use the analysis described in (a), above, to determine what new measurements would most significantly constrain biosynthetic potential, when added to a specific set of existing observational constraints. Second, we will evaluate, quantitatively, how forthcoming measurements (e.g., the suite of analyses that Europa Clipper will bring to bear) can help in resolving biosynthetic potential. In doing so, we will help to establish an interpretive framework that anticipates those measurements. Finally, we will quantify how specific enhancements in measurement capability may improve the ability to resolve biosynthetic potential. For example, while Galileo’s magnetometer investigation provided broad constraints on ocean salinity, the ICEMAG/PIMS investigation on Europa Clipper will make this measurement with significantly greater precision. Will this serve to constrain biosynthetic potential more precisely? When applied to a broader range of possible measurements, this type of analysis will provide underpinning to science definition activities, by quantifying the impacts of instrument performance in relation to assessment of biological potential.

This Investigation, as an attempt to model ocean world geochemistry on a much larger scale than has previously been done, will be computationally intensive. We estimate that it will be necessary to span a matrix of compositions and conditions representing approximately 10 million unique reaction path calculations. Those calculations will yield up to 50 billion primary

21 and derivative outputs, upon which our analyses and operations will be conducted. We have prepared for this in two ways: (1) The reaction path calculations and operations on the resulting database will be conducted using the Pleiades supercomputer at NASA Ames. In preparation for this proposal, Research Associate Sanjoy Som, who has previous experience in coding for the parallel architecture of Pleiades, assessed its performance on a suite of benchmark calculations that correspond closely to those proposed for Tasks 3-5 and 3-6. (Specifically: Pleiades ran a matrix consisting of 6400 reaction path simulations using EQ3/6, followed by extraction of specific data products.) On this basis, we estimate that Pleiades at full capacity would complete 10 million reaction path simulations in approximately 10 minutes, whereas a typical desktop would require > 1 year. More realistically, given the typical subscription rate of Pleiades, we estimate that the task could be completed in approximately 3 hours. (2) To ensure that the database created in Task 3-5 has maximum utility for the operations and experiments of Task 3-6 and, going forward, for the broader astrobiology community, we have arranged for Som to attend the Data Sciences Immersive course (General Assembly) in Project Year 1. This course, tailored to the “big data” applications typical of the Silicon Valley tech community, will enable Som to bring current best practices and statistical methodology in data science to the creation and use of the large database proposed for this work.

The goal of Investigation 4 is to empirically constrain how geochemical processes might affect the biological potential of ocean worlds and how life, if present, might use the energy and matter that are made available through those processes. Together, Investigations 2 and 3 will provide a theoretical framework for the geophysical and geochemical conditions that may exist for seafloor fluid flow on ocean worlds with rocky seafloors. In isolation, however, these theoretical assessments cannot capture all the salient aspects of ocean world geochemistry, such as how reaction kinetics might influence reaction pathways and the metastable formation of minerals and aqueous species. Nor can they capture the influence of environmental variability on biological potential – for example, the extent to which changes in temperature, substrate availability, or any other physico-chemical factor might limit biological potential. This Investigation will augment and inform our team’s modeling efforts through geochemical and coupled geochemical/microbiological experiments directly relevant to assessing biological potential on ocean worlds. Specifically, this Investigation is tailored to provide empirical constraints and feedback to our overall effort in areas where existing empirical data are sparse. In Tasks 4-1 and 4-2, we will use abiotic geochemical experiments to examine the production and persistence of chemical species containing the biologically essential elements C, H, N, O, P, and S during water-rock reactions. The experiments will focus on: (a) examining geochemical processes that are predicted to occur on other ocean worlds; (b) constraining the kinetics of reactions that are most relevant to biological processes (e.g., production of H2); and (c) conducting experiments across a range of conditions that are relevant to ocean worlds, but not well represented in studies to date. In Task 4-3, we will constrain the relationship between energy flux and biological productivity and yield, under conditions and with metabolisms relevant to ocean worlds. In particular, we will establish how environmental variability (e.g., fluctuations in physical conditions and/or resource fluxes) might influence energy partitioning and utilization by microbes.

22 The experimental work conducted in this Investigation will be iterative and closely coordinated with ongoing work in Investigations 3 and 6. For example, this Investigation will empirically test Investigation 3 model outcomes through abiotic laboratory experiments that use the same composition inputs and reaction conditions, with emphasis on reaction products (e.g., metabolically relevant redox-couples) that determine biological potential. In turn, the results of the abiotic geochemical experiments (Tasks 4-1 and 4-2) will inform the design of coupled geochemical/microbial experiments (Task 4-3) as well as Tasks 6-1 to 6-4 in Investigation 6.

Task 4-1. Aqueous Carbon Geochemistry. Organic compounds could serve as an important source of energy and carbon on ocean worlds (Waite et al., 2017). A broad array of organics can serve as microbial substrates, and utilization of one-carbon compounds such as CO2, formate, and CH4 is prevalent in diverse rock-hosted chemosynthetic communities on Earth (Takai et al., 2004; Brazelton et al., 2006; Flores et al., 2011; Reveillaud et al., 2016). Assessing the potential for formation of such compounds under conditions relevant to ocean worlds thus constrains a potentially important contribution to their biological potential. In general, the formation of reduced carbon compounds can be attributed to three processes: “abiotic” formation involves the reduction of CO2 or CO by purely chemical processes, “thermogenic” formation involves the thermal decomposition of longer chain compounds and/or macromolecular material, and “biogenic” formation refers to the net production of organic compounds by living organisms. To the extent that carbonaceous chondrites may contribute significantly to the rock composition of ocean worlds, there is substantial potential for the thermogenic formation of organic alteration products during water-rock reactions. The presence of such compounds would have important implications for the biological potential of ocean worlds. Moreover, many of the longer chain organic alteration products have very low aqueous solubility, and may form discrete organic-rich liquid and solid phases with densities below that of liquid water. Upon release at the seafloor, these buoyant, low density phases could, for example, ascend through the water column and be expressed outward as far as the surface of an ocean world where their presence could provide strong indication of thermogenic processes in that body’s rocky interior (see also Investigation 6). Accordingly, we will conduct hydrous pyrolysis experiments that examine the thermogenic production of volatile, liquid, and solid-phase alteration productions during the heating of carbonaceous chondrites (to be sourced, provisionally, from the Arizona State University meteorite collection) in the presence of liquid water. We will build on the results of Sephton (1998, 1999, 2000) by providing quantitative information for the abundance and composition (isotopic and chemical) of liquid and volatile organic compounds generated during the heating of macromolecular organic matter in carbonaceous chondrites over a range of temperatures (100 to 350°C). These data will provide insights into the rates and mechanisms of thermogenic processing that can be used to extrapolate the results to a broader range of environmental conditions (c.f. Lewan, 1985; Seewald et al., 1998). This will help to provide empirical constraints across a broader portion of the parameter space considered in Investigation 3. Using the inventory of cometary volatiles created in Task 3-3 and theoretical predictions of Task 3-4, we will design and conduct experiments to empirically constrain how molar abundances of organic solutes such as methanol, formaldehyde, and acetylene influence the pH and redox state of aqueous fluids. These experiments will identify specific reaction pathways that regulate the formation of organic alteration products, including higher molecular weight compounds produced by polymerization reactions. Inclusion of rock forming minerals and sources of S and N in these experiments will allow us to establish important linkages between organic and inorganic transformations and refine the predictive capability of theoretical models.

23 We will also investigate the potential for abiotic synthesis of organic compounds in the rocky interiors of ocean worlds. These experiments will explore how the activities of H2 and aqueous sulfur species might influence organic transformations in water-rich systems: (a) Role of Hydrogen. Previous experimental studies have demonstrated that Fischer- Tropsch-type synthesis reactions are extremely limited under hydrothermal conditions unless a gas phase is present (McCollom & Seewald, 2007; McCollom et al., 2010). The stability of a gas phase in a liquid ocean is controlled by temperature, pressure, and the activity of dissolved gases such as H2. The ocean worlds of the outer solar system vary significantly in their gravity and depth of ocean and ice cover (Hussman et al., 2015), so that seafloor pressures may also differ significantly (Fig.4.3). By directly affecting the potential for gas phase formation, these pressure differences could significantly influence the extent of gas phase Fischer-Tropsch-type reactions. For example, at a presumed pressure of 10 MPa at the Enceladus seafloor (McKinnon, 2015), aqueous fluids would only require 87 mmolal H2 to form a gas bubble at 1°C assuming ideal behavior. Even at the 200 MPa inferred for the Europa seafloor (Hussman et al., 2015), only 251 mmolal H2 would be required for gas bubbles to form (Kelley, 1960; Wagman et al., 1982; Shock et al., 1989). Thermodynamic models for serpentinization of ultramafic rocks indicate that this amount of H2 is formed at water/rock ratios close to unity (Klein et al., 2009, 2013). We will evaluate the potential for abiotic synthesis on ocean worlds as a function of temperature and pressure, through experiments purposefully designed to develop H2-rich bubbles within the reaction vessel. These experiments will utilize serpentinization of ultramafic lithologies as the mechanism to generate H2 (rather than simple addition of H2), in order to understand the influence of H2 fugacity on gas phase synthesis of organic compounds in the presence of naturally occurring mineral assemblages that may contain catalytically active minerals such as magnetite and awaruite. Results from these experiments will be coupled with thermodynamic models that predict H2 generation (Investigation 3) and physical models that constrain water/rock mass ratios during fluid flow (Investigation 2) to constrain the delivery of aqueous organic compounds to near-seafloor mixing environments on ocean worlds. (b) Role of Sulfur. Experiments will also be conducted to explore the influence that aqueous sulfur species and sulfide minerals have on hydrothermal organic reactions. Notably, oxidative degradation of hydrocarbons is expedited in the presence of aqueous sulfur species and has previously been attributed to their catalytic activity (Seewald, 2001). A variety of transition metal sulfides are known to be catalytically active in the formation of alkyl thiols, organic acids, and peptides (Heinen & Lauwers, 1996; Huber & Wächtershäuser, 1997, 2003; Huber et al., 1998, 2012; Cody et al., 2000, 2004). The presence of aqueous sulfur species may also facilitate alternative reaction pathways. For example, we will test whether the abiotic step-wise reduction of CO2 to CH4 through formic acid, formaldehyde, and methanol intermediates (Seewald et al., 2006) may also proceed via an analogous pathway involving thioformic acid, methanethial, and methanethiol intermediaries. Experiments examining the role of sulfur will involve the heating of aqueous solutions containing inorganic carbon sources (CO2 or CO), H2, and S (added as aqueous H2S or sulfide minerals) at temperatures from 150 to 400°C. Selected minerals (transition metal sulfides, oxides, and alloys) will be added to experiments focused on heterogeneous catalytic activity.

Task 4-2. Hydrogen Generation. Biogeochemical processes that result in the formation and consumption of H2 are a key aspect to assessing the biological potential of ocean worlds, owing to its highly reducing nature and ability to fuel microbial metabolism. On Earth, H2 production is ubiquitously associated with aqueous alteration of rocks that contain ferrous iron and/or organic matter. Recently, Waite et al. (2017) concluded that there is ongoing hydrothermal activity within the Enceladus silicate core based on their detection of H2 by the Cassini INMS instrument. While this was a stunning discovery, the origins of the detected H2 remain unknown. Waite et al. (2017) postulate that pyrolysis of organic matter and/or oxidation of hydrated reduced rocks in

24 Enceladus’ rocky interior during hydrothermal alteration could release H2 to circulating fluids. But, presently, there remains a paucity of experiments that have examined H2 production or consumption across the range of conditions that are most relevant to ocean worlds. Experiments conducted under this task will react carbonaceous chondrites with aqueous fluids as a function of temperature and pressure to examine H2 generation during the thermal alteration of primordial organic matter. Previous experimental studies have demonstrated that water and organic compounds are highly reactive with respect to each other and may generate H2 (Seewald, 1994, 2001; McCollom and Seewald, 2001; Yang et al., 2012; Shipp et al., 2013). For example, aqueous ketones have been shown to form organic acids and H2 according to the reaction:

at elevated temperatures (Seewald, 2001). Other reactions, such as the formation of alkenes from their corresponding alkanes and the formation of alcohols from ketones, have been shown to reach metastable thermodynamic equilibria involving H2, representing an additional source of H2 (Seewald, 2001; Yang et al., 2012; Shipp et al., 2013). The implications of such reactions are profound for the availability of H2 during thermal alteration of organic matter, since the amount of H2 generated is not limited by the composition of precursor organic matter but, instead, may be regulated by the reaction of aqueous organic compounds with H2O. Within this Task hydrous pyrolysis experiments examining the generation of H2 (and aqueous carbon species) will be complemented by experiments containing model compounds to examine organic transformations that regulate the stability of specific compound classes. Minerals will be added to these experiments to regulate redox, sulfur fugacity, and/or pH (c.f. Seewald, 2001; Shipp et al., 2013). By monitoring the abundance of reactants and products we will be able to determine the mechanisms of these reactions and predict how these compounds influence H2 abundance in diverse seafloor environments. Additional experiments will be conducted to identify the production of H2 from redox reactive mineral assemblages during aqueous alteration reactions over a range of temperatures and pressures. We will begin by examining the oxidation of hydrated ferrous-bearing assemblages as proposed by Waite et al. (2017), where H2 generation is decoupled from the process of serpentinization. While there have been numerous experimental investigations of H2 generation during serpentinization of ultramafic rocks, including studies led by our colleagues in the Rock Powered Life CAN7 NAI team, experiments examining generation of H2 during oxidation of reduced hydrated rocks and other ferrous-iron bearing rocks are lacking. Subsequent experiments will rely on the results of the geochemical and physical modeling in Investigations 1 and 2, and to identify physical conditions and mineral assemblages relevant to the production of H2 on ocean worlds. For example, as discussed for Investigation 3, equilibrium models predict that H2 generation during basalt alteration is dependent upon the Al2O3 content of basaltic rocks and not just the FeO content. Experiments can be used to verify such a hypothesis by constraining kinetic barriers that may influence alteration mineralogy and reaction pathways responsible for the production of H2.

Experimental Approach: Abiotic water-rock interaction experiments will be conducted at WHOI (see 9. Facilities & Resources). Closed system experiments will employ flexible-cell hydrothermal apparatus consisting of a gold reaction chamber and a titanium closure assembly (Seyfried et al., 1987). The flexible reaction cell is contained within a steel pressure vessel that is heated in a tube furnace - an approach that we have used extensively over 25 years in the study of aqueous organic transformations at elevated temperatures and pressures (Seewald,

25 1994, 2001; McCollom & Seewald, 2001, 2003a,b, 2006; Seewald et al., 2006). Importantly, the flexible-cell hydrothermal apparatus permits internally filtered fluid samples to be withdrawn at the temperature and pressure of an experiment, avoiding potentially ambiguous retrograde reactions that may occur during a prolonged quench process. This allows reaction progress to be monitored as a function of time. “Flow-through” experiments focusing on kinetic rate expressions will be conducted using a simple open-system flow through hydrothermal reactor at WHOI (in this case, a low-flow, low volume system ideal for abiotic reactions). Flow-through experiments are well-suited for the determination of reaction rates because key variables such as fluid composition, temperature, pressure, and flow rate (residence time in the reactor) can be modified easily during the course of an experiment, facilitating the development of rate expressions and constants. All experiments will be accompanied by a comprehensive suite of chemical analyses that will quantify dissolved gases, organic compounds, and inorganic ions and neutral species using established techniques (Seewald et al., 1998; McCollom et al.,2001; Seewald, 2001; Reeves et al., 2012; McDermott et al., 2015). For experiments that examine the generation and stability of organic compounds, we will also measure carbon and hydrogen isotopic compositions routinely. Stable isotope analysis represents a powerful tool for understanding the origin of carbon compounds on Earth. By examining isotope fractionating effects and processes in well characterized systems under ocean-world-relevant conditions, the results of these experiments will help to establish a framework for the interpretation of future isotopic measurements from, for example, MASPEX on Europa Clipper (see: 8. Relevance).

Task 4-3. Biological Activity Experiments. The data resulting from the theoretical modeling in Investigation 3 and the abiotic experiments of Tasks 4-1 and 4-2 will set the stage for microbiological experiments that, in turn, will further constrain how water-rock interactions can influence biological potential. The experiments to be conducted will provide ecologically-relevant insights into the fate of matter/energy derived from abiotic processes, the partitioning of matter/energy for maintenance and growth, and, ultimately, the net efficiency of matter/energy harvesting by microbes that are our best extant analog for life on other planetary bodies. Much of what we understand about these aspects of microbial physiology derives from studies of model organisms that thrive under laboratory conditions. Here, we will use pure cultures and co- cultures of organisms chosen to reflect the specific metabolisms and environmental niches most relevant to biological potential on ocean worlds. Primarily, these will be non-model microbes with chemolithoautotrophic metabolisms (metabolisms that use inorganic chemistry to supply energy and CO2 as a source of carbon) that have been cultured from Earth analog habitats that Table 3.1. Example organisms available to be used in Task 4-3 experiments.

Domain Organism Source Temp pH Electron Electron Obl/Fac1 Reference Range (°C) Range Donor Acceptor

Archaea Methanogenium marine 5 to 25 5.5 to H2 or CO2 Obl Chong et al. marinum sediments 7.5 COOH 2002

Methanococcus marine <20 to 55 5.5 to H2 or CO2 Obl Kendall et aeolicus (Nankai- 3) sediments 7.5 COOH al. 2006 2- Bacteria Halomonas NP3 marine crustal 15 to 40 ND S2O3 NO3 Fac Angermeyer fluids 2017

Lebetimonas NWR marine vent 40 to 60 6 to 8 H2, Sulfur Obl Meyer and fluids formate Huber 2014

Desulfonatronum soda lake 15 to 48 8 to 10 H2, SO4, Fac Pikuta et al. thiodismutans 2- 2003 formate, S2O3 , ethanol 2− SO 1Obl = obligately autotrophic; Fac = facultatively autotrophic

26 may be relevant to ocean worlds. Our initial focus will be on microorganisms recovered from diverse aquatic environments, including subseafloor crustal fluids, marine sediments, alkaline lakes, and hydrothermal vents, with example organisms shown in Table 3.1. However, the choice of conditions and organisms will be tailored in response to findings (e.g. predictions of important energy sources, or specific environmental conditions) from Investigations 2, 3 & 4, and through interactions with the broader community via our Workshop Without Walls activities. In our experiments, we will use three approaches that will be followed: (a) batch cultivation (closed systems, range of pressures); (b) gas-flow controlled continuous cultures (chemostats, flow-through systems, at atmospheric pressure), and (c) high-pressure gas-flow controlled continuous cultures (chemostats, flow-through systems, under pressure). Batch incubations will focus on examining the net productivity and biosynthetic yield of organisms supplied with prescribed quantities of substrates. Out initial experiments in this Task will involve just one variable: e.g. the concentration of the relevant substrate(s). Next, other compounds such as co- products, or other relevant factors such as temperature, will be added or varied to determine whether they positively or adversely affect metabolic activity and, ultimately, biological potential (because biological potential is ultimately the sum of factors that support as well as deter the generation and/or activity of organisms). Batch experiments will initially be conducted at ~1-5 atm (about the pressure limits of serum vials), and then select organisms will be tested at relevant pressures (up to 400 atm) in high-pressure batch reactors. Although such batch experiments are limited (because they are conducted in a closed system), they provide an excellent high-throughput means of assessing the microbes that warrant the most attention. In addition, the tiered approach described here allows for timely feedback between theoretical modelers and experimentalists during Phase 1 of the project. Batch experiments will also offer an opportunity to place constraints on the maximum biomass yields that can be attained per unit substrate (biosynthetic potential, as described in Task 3-5), and thereby provide empirical constraints to our first Synthesis Activities at the very outset of the project (Table 4.2). The results of the batch reactions, together with results from Tasks 4-1 and 4-2 as well as from Investigations 3 and 6, will inform a series of experiments using gas-flow controlled continuous cultures, or flow-through chemostats (Herbert et al., 1956; Novick and Szilard, 1950; Cypionka 1986). These experiments are designed to quantify the maintenance energy and biosynthetic yield of a subset of anaerobic, autotrophic microorganisms studied in the batch experiments. Our goal is to investigate select microorganisms that show the greatest differences in growth rate, biosynthetic yield or any other relevant factor. We will measure the growth and metabolite production rates for representative microorganisms at varying pH, temperature, redox potential, and other variables (e.g. H2), and then calculate growth and maintenance energies to accompany these tested environmental variables (Hoehler and Jørgensen, 2013; Ver Eecke et al., 2012; Cypionka, 1986; Seitz et al., 1990). Such experiments are critical in the context of our Synthesis Activities, which will seek to constrain the potential of ocean worlds to support standing biomass on the basis of energy fluxes. While a rich body of literature has sought to quantify microbial maintenance energies (Tijhuis et al., 1993; van Bodegom, 2007), there is a paucity of such data for the metabolisms and conditions most relevant to consider here. Whereas batch incubations provide a robust means of placing the simplest, broadest constraints on abiotic-biotic relationships, and chemostats afford the best opportunity to make robust estimates of growth and maintenance energies, maintaining microorganisms at environmentally- relevant conditions provides the most meaningful measure of organismal tolerance (Smith et al., 1995). In any ecosystem, the existence, abundance and distribution of a given organism (e.g. ecotype or species) reflects that organism’s capacity to thrive within a range of physical and chemical conditions, beyond which a population cannot survive over time (Schimel et al., 2007). Moreover, a key aspect of determining an ocean’s biological potential is to understand the extent to which temporal or spatial changes in physico-chemical conditions may restrict an

27 organism’s function. Here, we aim to determine how changing those physico-chemical conditions affect microbial growth and maintenance energies. To that end, we will conduct a series of high-pressure (up to 400 atm), gas-flow controlled continuous culture chemostat experiments, in which we vary and co-vary key parameters to determine the net effect on microbial activity and, ultimately, growth. These multi-stressor studies will allow us to determine how an organism’s realized niche is influenced by co-occurring physiological stressors (note that for these experiments we will use artificial fresh- or seawater when possible, or minimal media if necessary, to ensure that the results are as relevant to nature as practical). In these experiments, we will synthesize the data from the theoretical and empirical geochemical efforts, as well as the batch and chemostat microbial studies, to conduct experiments in which we determine the physical and chemical limits of 5 representative microbes (Table 3.1). First, we will provide a seed population of the target microbe with the appropriate pressure, temperature and substrates needed to facilitate steady state growth. Next, we will vary one key parameter (e.g. temperature) continuously over time, and across the known limits of that microorganism. To this variable we will add another variable, (e.g. pH) – again, across the known limits of that microorganism, as established from batch and chemostat experiments. We will then introduce periodicity in substrate availability and, where appropriate, (and in collaboration with Investigation 6), the provision of particulates that may serve directly or indirectly as electron donors. As shown by multi-stressor experiments, simultaneous variations in Figure 3.11 Chemostats afford the robust means physico-chemical conditions are what truly of examining maintenance energy in microbial define the niche, or “realized” niche of any cultures (from: Hoehler and Jørgenson, 2013). organism (Harrison et al., 2013). These experiments provide an important check on theoretical and empirical estimates of maintenance energy that are based on static environmental conditions and substrate flux. Because such estimates will be a necessary component in any effort to constrain biological potential (not just our own), it is essential to understand how they may vary when environmentally realistic perturbations are introduced.

Experimental Approach - Biological activity experiments will be undertaken in Co-I Huber’s Microbiology laboratory at WHOI and Co-I Girguis’s Geobiology laboratory at Harvard. Both Co- I’s have conducted microbial incubations and experiments for the last ~20 years with microbes and materials from a variety of marine habitats, including methane seeps, hydrothermal vents and lower-temperature crustal aquifers (Girguis et al., 2003; Ver Eecke et al., 2012; Meyer and Huber, 2014; Nyholm et al., 2008; Meyer et al., 2016). For batch experiments, well-described anaerobic techniques (e.g. Sowers and Noll, 1995) will be followed, including using an anaerobic chamber for distributing sparged media into culture vessels and using a high- pressure gassing manifold for exchanging headspace or adding positive pressure to individual vessels (Balch and Wolfe, 1976). For batch experiments at high pressure, Isobaric Gas Tight (IGT) samplers will be used (Seewald et al., 2002), allowing for fluid withdrawal from, and additions to, the culture over time, all while maintaining high pressures (McNichol et al., 2016). For chemostat experiments (Fig.3.11) Ace Glass anoxic bioreactors will be used with instrumentation for controlling a variety of parameters including gas blend and flow, temperature, and pH (e.g. Cypionka, 1986; Ver Eecke et al., 2012). High pressure experiments will be conducted at Harvard (see: 9. Facilities).

28 Thus far, we have described a series of Investigations that our team will conduct to improve our understanding of how the conditions for life, and/or life itself, could be sustained in association with seafloor fluid flow and water-rock interactions close to the seafloor of an ocean world. In this investigation, we will explore the processes by which any products or indicators of those processes could be dispersed within an ocean world and, in particular, how they might be transported upward within the oceanic water column as far as the ice-water interface. From there (as being actively investigated in the NAI CAN7 NAI Icy Worlds project) such materials might be expressed outward to the surface where they could be detected by ocean world exploration missions. While circulation processes on ocean worlds are of great intellectual interest in their own right, the primary role of this Investigation is to constrain the pathways and associated timescales for tracers indicative of evidence for life and/or conditions suitable to sustain life, to be transported as far as the ice/ocean interface at the top of any ocean world’s water column. For ocean worlds in the outer Solar System, distant from the Sun, the presence of thick ice crusts covering the ocean preclude the presence of any meteorological (atmosphere-ocean) activity at the surface. Consequently, these oceans must be driven in a fundamentally different way from that on Earth (see review by Vance and Goodman, 2009). Here, we propose to use numerical experimentation to explore a range of possible ocean circulations that could exist on ocean worlds with an emphasis on those driven from below by geothermal heating and those driven from above through interaction (both thermally and via melting/freezing) with an overlying ice shell. Possible drivers of circulation from the seafloor are discussed in some detail in Investigations 1 and 2. That work will constrain the likelihood of convection within the planetary interior (giving rise to some form of tectonics ± volcanism), predicted lateral variability in seafloor topography, and predictions on the styles and associated magnitudes of any seafloor fluid flow. For circulation driven from above, any evidence of geographical variations in both ice thickness and lateral movement of ice, – for example, as evidenced by resurfacing processes in the case of Europa (Greenberg and Gessler, 2002; Kattenhorn and Prockter, 2014) – would imply that there must be melting and freezing of the ice. In that case, if melting does not balance freezing locally, horizontal salinity (and, thus, density) gradients will be created beneath the ice shell, resulting in a salt-driven circulation. Forcing by breaking internal waves, likely induced by tides, would also be expected to drive oceanic currents. Understanding the relative importance and interplay between these differently forced circulations, illustrated in Fig.3.1, represents a key challenge for Investigation 5. In turn, this work will provide an essential foundation for Investigation 6 which will investigate the formation and transformation of potentially diagnostic (bio)geochemical tracers within an ocean world’s water column as well as our Synthesis Activities investigating biosignature potential. Key questions that this Investigation will address include: • What is the nature of any ocean circulation driven by heating from below? Can diagnostic indicators of seafloor environmental conditions and or signatures indicative of life be communicated across the entire vertical extent of the water column, or will any effects arising from seafloor fluid flow only be felt locally, in the abyssal ocean and/or close to their source? • What is the nature of any salt-driven circulation on ice-covered ocean worlds? What is its connection to patterns of ice shell melting and freezing and freshwater transport within the ice shell? How does it interact with the thermally-driven circulation?

29 • Under what circumstances is the circulation of an ocean world rotationally-controlled? What would the implications be for the circulation of an ocean in a deep spherical shell? • How might seafloor-derived materials be transported from the seafloor to the base of the ice- shell? What are the residence times of suspended and dissolved materials in the ocean? Our numerical experiments will explore the widest possible oceanic parameter space (rotation rate, gravity, water depth, density stratification, ocean salinity) to elucidate the different circulation regimes that could arise on ocean worlds and to determine the key drivers for different scenarios. In the general case, we anticipate that circulation patterns may consist of separate but interacting vertically stacked circulation cells whenever there is forcing at both the upper and lower boundaries. We will consider both forcing instances, as follows: (a) Hydrothermal activity driven from below. Tidal heating of an ice shell can lead it to thin, but its basal temperature will not change because it only depends on the freezing point of water and this freezing-point temperature is a rather weak function of pressure. As a result, the ocean below any ice shell is likely to be well mixed and presented with an essentially isothermal upper boundary condition (Vance and Goodman, 2009). Very general considerations (Sandstrom's theorem, translated by Defant, 1961) suggest that an ocean driven only by warming at its upper surface must have a circulation whose strength and penetration depth is set by the energy available for mixing of buoyant fluid downwards. It is, thus, likely that any primary thermally- driven circulation on an ocean world must be from below, associated with geothermal activity. Based on the ocean worlds discovered thus far in the Solar System we must consider: (i) the possibility of extremely deep oceans (ii) that they may be rotating rapidly, at rates comparable to Earth, and (iii) that gravity and hence buoyancy fluxes can be much lower than on Earth. One might, thus, anticipate that the associated ‘Natural Rossby number’ (a measure of the rise distance in a rotation period compared to the total depth) could be small. In this case any buoyant (e.g. hydrothermal) plumes arising from the mixing of seafloor fluid flow with overlying ocean water will “feel” rotation (Jones and Marshall, 1993; Maxworthy and Narimousa, 1994; Speer and Marshall, 1995; Marshall and Schott, 1999; Goodman et al., 2004). The resulting large-scale circulation induced by heating from below would likely drive zonal jets because of the constraints imposed by rotation (see review by Collins and Goodman, 2007). On ocean worlds with very weakly stratified oceans and strong bottom heating rates, it may be possible for hydrothermal plumes to rise from the seabed all the way to the ice shell. For example, through numerical simulation, Soderlund et al. (2014) have argued that ocean-driven heating of Europa's icy shell can be achieved through convection which has a very much larger Rossby number (of order unity) inducing 3-D rather than 2-D turbulent convection. However, those predictions were for a very different parameter regime than that explored in an earlier study (Goodman et al., 2004) of venting on Europa, reflecting how much work remains to be done in this area. At some level in the water column, convective, plume-driven vertical transport must interact with a (salt-driven) overturning circulation driven by under-ice processes (see next section). On ocean worlds with a stratified water column and topography, tidal forcing will also create internal waves. Near the seafloor, this would be expected to result in turbulence and mixing that propagates upward into the overlying water column to heights above the seafloor that are directly comparable to any regional-scale seafloor topography (Investigation 1). Our work will build on prior studies by Goodman et al. (2004) and Soderlund et al. (2014) who used quite different parameter regimes for convection on Europa, and to help to place that earlier work in context. For example, both of those studies considered the case for a freshwater system that was thermally driven. But, as we now discuss, the circulation on a salty ocean world could be quite different. (b) Salt-driven circulation drive from above. Salt-driven circulation regimes on ocean worlds can arise due to salinity variations at the upper boundary (Vance and Goodman, 2009; Ferreira et al., 2011). Such salt-driven circulations, a relatively unexplored area of research for

30 ocean worlds, would be intimately linked to lateral transport within the ice shell, associated with resurfacing processes. Wherever the ice shell is thicker, under-ice waters would likely be saltier than where the ice is thinner, because ice formation causes the release of salty brine. Since salty water is heavier than freshwater, one would then expect a salinity-driven overturning circulation which would transport fresh water and heat from thin-ice regions to thick ice regions, off-setting the salinity and heat imbalance. These are represented by the purple arrows in Fig.3.1. As with circulations driven by heat fluxes at the upper surface, mechanical mixing is required to balance the buoyancy loss of the downward limb of the circulation and is expected to affect the strength and depth penetration of the salt-driven circulation. An illustration of one kind of salt-driven circulation that could be expected on an ocean world (Fig.3.12) is salt-driven overturning circulation on an Earth-like planet in an ice-covered state. The meridional salt gradients, related in this case to meridional temperature gradients at the surface, drive circulation that transports salt from the poles to the equator, balancing the freezing/melting pattern and enabling a steady-state circulation. The pattern of freezing/melting at the bottom of the ice shell also implies thinning of the ice shell at the equator and thickening at the poles, which is balanced by a pole-to-equator flow of ice (similar to the “weak hydrological cycle” limit of Pierrehumbert et al., 2011). The interplay of the salt- and the thermally-driven circulations, in conjunction with mechanical mixing, will be crucial to understanding the circulation on ocean worlds. For example, Thomas et al. (2016) have reported evidence for a global ocean underlying a relatively thin ice shell on Enceladus while Le Gall et al. (2017) have reported further observations from Enceladus that imply the presence of a heat production and transport system over the South Pole. Linking such heat and salt driven circulations and the relative importance of the two, will be an important goal for this Investigation 5. For any given ocean world, we must anticipate different forcing processes acting over different depth ranges. Consequently, for any general case, we should expect overturning circulations with multiple distinct but interacting vertically stacked cells, perhaps analogous to the deep- and bottom-water cells of the Atlantic meridional overturning circulation that oceanographers are extremely familiar with Figure 3.12 Salinity-driven circulation on an ice-covered Earth-like planet (Ferreira et al., 2011). The overturning circulation (Sverdrups) is on Earth. The relative represented by the red contours. Sinking occurs at the poles, where the extent and strengths of ice is thicker and the ocean is saltier; upwelling occurs at lower latitudes these cells will depend where ice is thinner and the ocean is fresher. The grey color and labeled on the relative strength white contours represent potential density (kg/m3) referenced to the of the different forcing surface. The y-axis shows depth in meters. processes, with density stratification,

31 topography and rotation also playing roles. Any overturning circulation will, necessarily, also be associated with horizontal (more correctly, isopycnal = constant density) flows. For horizontal circulation, rotation is expected to play a controlling role with effects including eddies and zonal jets. Additional horizontal currents may include directly driven flows resulting from laterally varying interactions at the ice-ocean and ocean-seafloor interfaces. In the upper water column, we can anticipate circulation cells driven by fluxes of heat and fresh water from/to the overlying ice shell. At the lower boundary, heat fluxes across the seabed might arise from interactions with topography leading to vertical mixing and/or the presence/absence of inputs from seafloor fluid flow. High temperature hydrothermal plumes, as one example, have the potential to drive sub-global-scale circulations through the injection of mid-water buoyancy anomalies (Stommel, 1982; Hautala and Riser, 1993). We propose to investigate these circulation regimes and their interactions using a hierarchy of conceptual and numerical models of increasing complexity. The development of our models will be carried out in close consultation with Jason Goodman (NAI CAN7 Icy Worlds team), with whom we have collaborated in the past and with whom we have been in discussion during the preparation of this proposal. In Task 5-1, for example, we will establish the same 1D model already developed by Vance and Goodman (2014), and implement it within the MITgcm framework. This would then be expanded out into the new work focused on the 2-D and 3-D modeling in Tasks 5-2 and 5-3. These models would then be shared back to, and deployed collaboratively with Goodman, Vance and colleagues in the NAI CAN 7 Icy Worlds team as well as with the wider NAI community. Task 5-1. Establishing 1-dimensional (vertical) advection/diffusion models. This model, already developed by Jason Goodman and his collaborators in the NAI CAN7 Icy Worlds team, is forced by buoyancy input at the upper and lower boundaries. We will adapt these experiments to be run on the MITgcm to begin work within our Investigation 5. They are computationally cheap and will yield constraints on the vertical density stratification, sufficient to inform our initial Synthesis Activities (Table 4.2). From there we will be poised to build out from and extend this work. Task 5-2. Extension of the 1-D model to 2 dimensions. Expansion of our work into new areas of research will be achieved by including both horizontal advection and the modeling of how particles, as well as dissolved tracers disperse in the meridional plane. Such “zonal- average” models have been widely used previously in Earth-based studies of both atmospheric circulation and the ocean's Antarctic Circumpolar Current to investigate lateral variability. We expect them to be of great utility here as we begin to explore the roles that topography can play in ocean circulation, at both the seafloor and the ice-water interface. These models will also provide first indications of the timescales for the dispersion of both dissolved and particulate (bio)geochemical tracers, sourced from sites of seafloor fluid flow, through the ocean, important to Investigation 6, Task 6-4. Task 5-3 Full 3-dimensional general circulation models. Few studies have ever addressed the 3-dimensional ocean circulation of other ocean worlds. None have explicitly accounted for the ocean-ice interaction and a realistic representation of the coupled heat/water/salt fluxes at the ocean-ice interface. We will address both sets of circumstances in this study along with consideration of ocean interactions with the predicted topography of the underlying seafloor. Such processes are so fundamentally 3-dimensional in nature that they cannot be captured by current 1-D (radial) simulations. They can only be addressed using 3-D circulation models. Implementation: To complete the tasks described above, we will run an extensive program of numerical experiments using the 3-D general circulation modeling infrastructure of the MITgcm (see: 9. Facilities & Resources). MITgcm was developed by Co-I Marshall and his group and

32 will be configured specifically, under this investigation, for the study of circulation processes on ocean worlds. In addition to modeling the flow of fluids within the ocean, a particular advantage of the MITgcm is that it includes Lagrangian sub-models that we can utilize, readily, to investigate the fate of both neutrally buoyant substances and settling particles (critical to Investigation 6) as well as buoyant components (relevant to the potentially buoyant organic molecules described in Investigation 4, Task 4-1). Input parameters for the models include the equation of state for the seawater on any ocean world, gravity, orbital and rotation parameters, depth of water/ice layers, ice and seafloor topography, and the distribution of buoyancy input at the upper and lower boundaries. Our model experiments are expected to yield constraints on key parameters including ice thickness, interior density stratification, the planetary circulation of mass, heat and salt, as well as information on the Lagrangian pathways and timescales. [Note: Equation of state (EOS). Before starting work we will consult with the NAI CAN7 Icy Worlds team (Co-I’s Vance and Goodman) to take advantage of the latest updates from the important research that they are actively undertaking in this field (e.g. Bollengier et al., 2016; James et al., 2017).

Investigation 6 will explore the fate of key (bio)geochemical tracers formed during the mixing of subsurface fluids and ocean waters, to evaluate their potential as tracers for evidence of life and/or conditions suitable to sustain life. In our most recent work, we have revealed the surprising result that suspended particle aggregates formed in seafloor hydrothermal plumes (Fig. 3.13) can be distributed over planetary scale distances (thousands of kilometers) with the potential to upwell as far as the ocean surface along isopycnal (constant density) surfaces (Fitzsimmons et al., 2017). This is important because, on Earth, we know that suspended particles have two particularly valuable traits that ocean scientists are able to exploit when seeking to understand (bio)geochemical cycling in the oceans: (a) particles can be excellent recorders and reporters of biogeochemical conditions at the location where they first form; (b) particles are extremely effective at concentrating materials from an otherwise dilute ocean and generating micro-environments that can be conducive to life. Assuming the fundamentals of Earth’s ocean chemistry are not violated on other ocean worlds, we hypothesize that oceanic particles expressed onto the surface of other ocean worlds might offer particularly valuable targets that could be both detectable and provide diagnostic evidence for conditions within the underlying ocean. While concentrations of any given dissolved tracer may become increasingly dilute during mixing within an ocean world’s water column (Investigation 5) the advantage of particulate-phase tracers is that – while their concentrations may become similarly dispersed per unit volume of ocean water – individual ocean particles have the potential to preserve their integrity during emission outward to the surface of any ocean world where they might be exploited as priority targets for identification and characterization (e.g. NASA, 2017a; Porco et al., 2017). Accordingly, in this investigation we will conduct a series of laboratory experiments to test this hypothesis by generating and analyzing synthetic ocean particles formed under ocean- world relevant conditions in a systematic sequence of abiotic (inorganic, Task 6-1; inorganic + organic, Task 6-2) and biotic (Task 6-3) experiments. We will then investigate how those particles might be altered during transport through the oceanic water column (Task 6-4) and after being expressed onto the outer surface of an ice-covered ocean world (Task 6-5).

33 Figure 3.13 Images and elemental maps of particles formed during mixing between subsurface fluids and ocean waters at a seafloor hydrothermal field. These particles were collected in the >0.2 µm size fraction, and are composites of organic matter (including intact microbial biomass) and inorganic iron(III)-oxyhydroxide minerals. The size, morphology, and compositions of the intra- particle constituents were analyzed using X-ray absorption spectroscopy at the C 1s and Fe 2p edges (spectra not shown). (Source: B.Cron & Co-I B.Toner, unpubl. data).

The starting point for our investigations will be to select ocean world conditions that have been identified to be of particular relevance for biosynthetic potential in Investigations 3 and 4. As Investigation 5 proceeds, new insights for the trajectories and timescales for particle dispersion within any given ocean world (buoyant, non-buoyant and sinking particle dispersion will be modeled in addition to fluid dispersion) we will investigate how the (bio)geochemical signatures of suspended particles might evolve through alteration processes as they are transported. Both the formation and alteration aspects of our investigation will be critical because any instrument that analyzes particulate material at the exterior of an ocean world (e.g. Europa Clipper’s SUDA instrument – see: 8. Relevance) can only measure signatures acquired over that particle’s cumulative history. To interpret the significance of those observations with confidence will require a sophisticated process-based understanding of how those signals may have been acquired. Key questions that this Investigation will address, to meet this need, will include: • What is the continuum of particulate tracers that could form on ocean worlds? • How might those particles be altered during dispersion through the ocean water column? • What would their fate be, once expressed to the icy exterior of an ocean world?

Particles as (Bio)Geochemical Tracers: When applying the concept of treating any ocean world as a geochemical reactor, it is important to recognize that a vast array of reactants and products is possible. This is the emphasis of the massive computing power to be brought to bear in the geochemical modeling to be undertaken within Investigation 3. For laboratory based

34 investigations that seek to add value to that modeling program, however, this Investigation is faced with the same challenge discussed in Investigation 4: to select a subset of all possible experimental conditions that will be of greatest value to our team’s efforts – to improve the probability of future missions to detect and diagnose evidence for life or conditions suitable for life on other ocean worlds. Here, using our extensive experience in studying the biogeochemistry of Earth’s oceans and, in particular, the nature and fate of tracers indicative of seafloor fluid flow as they are dispersed through the oceans (German et al., 1991, 2016; Toner et al., 2009a,b, 2016), we choose to focus our efforts on the formation and fate of particulate phases. Within this context, particles can be inorganic or organic, pure phases or composites, crystalline or gels, abiotic or biotic, and mixtures of these various components (Fig. 3.13). Particles are important tracers of processes on ocean worlds because: (a) Particles can be recorders and reporters of biogeochemical conditions. Particles can provide insights into the conditions present at the time of formation, so long as one can account for the possible alteration processes those particles may have undergone since and, hence, know how to interpret time-evolved, accumulative observations. In recent work, silicon-bearing nanoparticles detected in the E-ring of Saturn have been attributed to submarine hydrothermal activity on Enceladus (Hsu et al. 2015). These particle properties have been used to estimate possible temperature and rock-water conditions at Enceladus’ seafloor. But those assumptions only hold if the silicon nanoparticles are de novo products of hydrothermal venting, unaltered by transport across many possible physical/chemical interfaces (seafloor to ocean interface; within ocean transport; ocean-to-ice interface; through ice transport). Through the research conducted here, we will experimentally address a range of subsurface fluid and ocean conditions for particulate tracer formation, and subject those tracers to conditions (physical, (bio)geochemical, transport time, exposure to radiation on ice-shell surfaces) to increase our understanding of how such processes might alter the characteristics of different particulate phases before they reach the stage at which they could be identified and characterized during future space missions. (b) Particles can act as vectors for concentrating materials and creating conditions relevant to biological potential in ocean environments. Particles are known to concentrate materials while in contact with water, including CHNOPS elements and other essential micronutrients (e.g. Fe), that would otherwise be much more dilute in their dissolved forms, dispersed throughout an ocean (e.g. Kiorboe and Jackson 2001; Stocker et al. 2008; Satinsky et al. 2014). Particles also create micro-environmental conditions that harbor geochemical conditions out of equilibrium with bulk conditions (e.g. Gieseke et al. 2006; Pallud et al. 2010; Han et al. 2012; Prairie et al. 2015). In essence, particles can serve as µm to mm scale “geochemical reactors” by sequestering nutrients and supporting chemical gradients in master variables such as redox and pH. In this investigation, we will experimentally address a range of inorganic-to-organic, and abiotic-to-biotic conditions for particle formation, transport, and alteration. The resulting tracer particles will be investigated using spatially resolved spectromicroscopy approaches to examine inter- and intra-particle size, morphology (external shape, internal texture), aggregation, elemental distribution/composition, and elemental speciation (for organics and inorganics).

Approach: We will build on Investigations 3, 4 and 5 to explore particles as potential tracers of the subseafloor processes and ocean conditions under which they are generated and altered prior to detection – i.e., the processes that occur after subsurface fluids are released to the ocean, and during mixing with ocean water, transport through the oceans, and exposure at the surface of an ocean world once they have been expressed through an ice-shell. The fate of ocean tracers during transport through an ice-shell is outside of our area of expertise and, further, is already being investigated elsewhere within the NAI community (CAN 7 Icy Worlds: Investigation 3 – see: 7. Other Institute Objectives). Using experimental laboratory-based systems, we will explore those characteristics that are indicative of processes/conditions to

35 which both biological and biosignature potential may be sensitive. We will examine a range of scenarios extending from abiotic-inorganic experiments, to abiotic experiments that blend key inorganic and organic constituents together, and then to experiments in which organic materials of biotic origin and microbial life are introduced. To begin our experiments, we will consult across our own team and also the wider NAI community, through the first of our proposed Workshops Without Walls for this project, to establish pertinent ranges of values for the following key parameters: • The temperatures and pressures for subseafloor fluid and ocean water mixing; • The compositions of the fluids, ocean waters and the range of mixing ratios to be used; • The major geochemical master variables, pH and redox potential, as they reflect rock types and different pairings of vent fluid and ocean water characteristics; • The presence of organic molecules in gaseous, dissolved, and particulate forms to represent biotic and abiotic sources; and • The non-model microorganisms to be used for our experiments.

Over the course of the project, design of our experiments will be informed by all of: (a) our knowledge of the variation in subsurface fluid compositions on Earth; (b) the modeling and experimental outcomes arising from Investigations 1-5, and (c) a continuing synthesis of the current state of knowledge (observations and hypotheses) for identified ocean world conditions (e.g. the wealth of information still arising from Galileo and Cassini observations at Europa and Enceladus). To begin work, we will generate and characterize de novo particle formation for an initial range of ocean world scenarios to examine processes and the resulting potential tracers. In addition, we will examine the alteration of a range of pre-formed particle types (size, morphology, composition, density, complexity) in different physical, chemical, and biological oceanographic scenarios to measure the overall fidelity of potential tracer signals under different ocean world conditions. Finally, we will subject potential tracers to a variety of ice-shell surface and burial conditions to examine the degree to which tracers will be preserved and detectable. For all experiments, the de novo, pre-formed, incubated, or altered particulate tracers will be subjected to a suite of X-ray spectro-microscopic and electron-microscopic analyses. These analyses will resolve size, morphology, degree of aggregation, composition, chemical speciation, and mineralogy. To complement these observations, and assess the degree to which particulate tracers will be detectable, existing and planned mission-specific observations (mass spectrometry, infra-red spectroscopy) will also be conducted on candidate particles generated by our experiments within Co-I Hand’s “Icy Worlds Simulation Laboratory” at JPL (see: 9. Facilities and Resources).

Tasks 6-1, 6-2, 6-3. Particulate tracer formation. This series of three interleaved Tasks will examine the characteristics of particle tracers at the time of their formation, when subsurface fluids mix with ocean water across a range of ocean world scenarios. For varying major chemical ocean compositions, we will examine three end-member possibilities that are relevant to biosignature potential: (a) an abiotic and inorganic ocean; (b) an abiotic ocean with organic compounds present; and (c) a biotic ocean with inputs of organics derived from microbes (cells, exudates, and biomass). Each of these families of ocean world conditions will then be examined under oxic and anoxic ocean scenarios with salt compositions informed by evolving interpretations of the observations from candidate ocean worlds - e.g. Carlson et al. (2009) and Vance et al. (2016) for Europa, Postberg et al. (2009), Glein et al. (2015) and Waite et al. (2017) for Enceladus. The constituents of the abiotic-organic experiments will be informed by the geochemical experiments of Investigation 4 (Task 4-1) and will include a range of molecules: carboxylic, amino, and sulfonic acids, sugars, urea, and thermogenic compounds such as thiophene (Sephton 2002; 2012; Gilmore 2014). The constituents of the biotic experiments will be determined by the microbiological efforts of Investigation 4 (Task 4-3). The same non-model

36 obligate and facultative autotrophs listed in Table 3.1 will be used as inputs to the “biotic” ocean scenarios examined in this Investigation. (Note: Investigations 4 and 6 will use the non-model microorganisms listed in Table 3.1, but other microorganisms may also be chosen, here, in response to Investigation 3, 4 & 6 findings).

The mixing of subsurface fluids with ocean waters to simulate venting processes and de novo particle formation will be accomplished using flow- through reactors at ocean world temperatures and pressures using Co-I Girguis’ “High Pressure Lab” (described in Investigation 4). Because the set-up of the flow- through reactors requires Figure 3.14. Flow chart showing major experimental tasks for Investigation 6. Experiments will examine the mixing of a range of some model and subsurface fluids (as informed by Investigations 3 and 4) with experimental products different scenarios for ocean water chemistry organic compounds and from Tasks within biology variously absent or present. Investigations 3 and 4, the first experiments will be conducted using preformed particles based on our knowledge of their characteristics in Earth’s oceans (as reviewed by Toner et al. 2016). We will synthesize preformed particles representative of the components of tracer particles from a range of vent types using established methods: for example, nanoparticulate pyrite and ferrihydrite mineral phases (Schwertmann and Cornell 2000; Gartman and Luther 2013). Particles representing the inorganic-organic composite nature of plumes will be synthesized with minerals having abiotic (organic-coated minerals; e.g. Smolensky et al. 2011) and biotic organic components (microbe- mineral flocs; e.g. Toner et al. 2005; 2012b; Bennett et al. 2014). The preformed and de novo particle tracers generated for the different Ocean World scenarios will be characterized (see next paragraph) and used as starting materials for Task 6-4 (transport and alteration) and Task 6-5 (preservation and detection on the icy exterior of ocean worlds). Particles from all Tasks within this Investigation will be characterized using a suite of spatially resolved imaging, spectroscopy, and diffraction methods that capture inter- and intra-particle morphology and composition (Fig. 3.14). The dual spectroscopy-diffraction approach allows for discovery and characterization of unanticipated organic and inorganic solid phases. These are methods that have been developed continuously by Co-I Toner and her colleagues over the past fifteen years for the grain-by-grain analysis of microbe-mineral composite particles, microbial mats, and vent-derived materials (e.g. Toner et al. 2005, 2009a,b, 2012a,b, 2014, 2016; Breier et al. 2009, 2012; Fitzsimmons et al. 2017). The core observations will include electron-microscopy and -microprobe analyses to be conducted at the University of Minnesota, and X-ray-microscopy and -microprobe analyses to be conducted at the Advanced Light Source, Lawrence Berkeley National Laboratory or other appropriate synchrotron facilities. Solid phase reaction products, i.e. particles, will be sampled from all proposed experiments using a series of filters (> 200 nm, > 20 nm, > 3 nm) following the methods of Fitzsimmons and Boyle (2014). Subsamples from all experiments will be examined by scanning electron microscopy (SEM) with elemental analysis (EDX/WDX) and transmission electron microscopy (TEM) with

37 selected area diffraction (SAED) using standard techniques. The SEM/TEM approaches will be crucial for describing any dispersed nanoparticulate phases due to excellent spatial resolution. Particle morphology and intra-particle composition will be measured using scanning transmission X-ray microscopy (STXM) and X-ray absorption near edge structure (XANES) spectroscopy for light elements (e.g. carbon, nitrogen, oxygen) and other particle forming elements (e.g. silicon, aluminum, sulfur, iron). STXM-XANES are excellent for fine-scale observations (10-20 µm fields of view with ~ 20 nm resolution) and reveal fundamental properties such as organic versus inorganic carbon, major classes of minerals (e.g. pyrite versus iron oxyhydroxide versus primary silicates). The mineralogy of particles, spanning crystalline to short-range ordered phases, will be described by X-ray microprobe diffraction (XRD) and X-ray absorption spectroscopy (XANES/EXAFS). These techniques are complementary to the STXM-XANES approach, excel at querying larger numbers of particles for quantitative analysis (larger spot size, ca. 1-5 µm), and can reveal changes in mineralogy and crystallinity.

Task 6-4. Particulate tracer transport and transformation. This Task will examine the transport potential and alteration of a range of preformed and de novo particle types (size, morphology, composition, density, complexity) under different physical, chemical, and biological oceanographic scenarios to investigate the overall fidelity of potential tracer signals under different ocean world conditions. The degree to which plume solids can act as tracers depends on how effectively and efficiently they are transported through the ocean: e.g. the residence time of the solid in suspension relative to the transport time to a location where it may be detected. Therefore, the size, density, and composition of the solids are of central importance. Solids in the nanoparticulate or colloidal size fraction (operationally less than 200 nm) have high transport potential. Solids with overall low density relative to the ambient ocean water also have high transport potential. In addition to transport potential, to serve as a utilizable tracer for astrobiology purposes, particles must retain information despite exposure to strong gradients in physic-chemical properties at environmental interfaces or long exposure times to milder disequilibrium conditions. For example, particles could experience dissolution of inorganic phases during dispersion (e.g. aluminum-bearing phyllosilicates dissolve as the aluminum concentration decreases). Particles could also experience oxidative or reductive processes leading to a wide variety of conflicting tracer signals. For example, particle size (but not necessarily density) could increase progressively if the oxidation of metals resulted in continued precipitation and aggregation of metal oxyhydroxide material. Conversely, reductive dissolution of metal oxyhydroxides or oxidative dissolution of metal sulfides could lead to the complete loss (dissolution) of a particle tracer over time. Oxidative or biological consumption of particulate organic carbon or other nutrient-bearing molecules during transport could result in the disaggregation particles and overall removal of an organic carbon signature. Therefore, informed by the modeling output of Investigation 5, this team’s task will be to design experiments that consider the suite of possible processes and how they might alter a solid phase tracer intercepted at any given point along the seafloor to ice-shell continuum. Preformed and de novo particle tracers will be incubated in large (40, 80 or 160 L) mixed-batch reactors that mimic gentle currents, low temperatures (ambient Earth pressure), and the range of (bio)geochemical regimes to be investigated. Based upon the “planktonkreisels” developed to keep gelatinous animals in aqueous suspension in the lab (Grieve, 1968), these reactors have been used by Co-I Girguis to keep particles suspended in solution for several months at a time (see: 9. Facilities and Resources). In this study, Girguis will adapt an existing 80 L “planktonkreisel” to maintain anaerobicity and use pre-defined media (e.g. anoxic seawater) to maintain suspended particles – including those with biotic components – over time intervals informed by the physical transport models developed in Investigation 5. To examine particle

38 alteration as a function of transport time, particles will be subsampled monthly and characterized as described above in Tasks 6-1 to 6-3. The data gathered from these experiments will be used to describe the tracer preservation, alteration, and destruction during transport. Subsamples of particles from this Task’s experiments will feed forward into the ice- shell investigations conducted in Task 6-5.

Tasks 6-5. Particulate tracer preservation and detection. In this Task we will seek to understand the fate of tracers after they are expressed outward to the exterior of an ocean world. These experiments, together with Task 6-4 in particular, will help us improve the confidence with which we can use (bio)geochemical observations made at the surface of an ocean world to interpret what astrobiologically relevant processes may be active, within. Once again, the nature of particulate (bio)geochemical tracers is important, here. Both dissolved and particulate tracers of seafloor processes may become increasingly dilute per unit volume of ocean water as they are mixed out within the water column. But, we hypothesize, particulate phases offer a particularly high potential to be readily discernable at the surface of an ocean world and to retain locally concentrated (on the scale of a micron) and potentially diagnostic information related to within-ocean conditions (NASA, 2017a; Porco et al., 2017). We will conduct vacuum chamber and irradiation experiments with tracer particles from a range of ocean world scenarios (abiotic-inorganic, abiotic-organic, biotic) to better understand whether tracers will be preserved and detectable on ice-shells or in planetary plumes. The particle-based experiments will be compared to materials deposited as dissolved constituents to help resolve post-depositional oxidation at the surface of an ice-shell. For example, is the presence of Fe(III) due to an oxidizing ocean, or oxidation after emplacement in the ice-shell? The tracers studied will be representative of a range of subsurface and ocean conditions, and we will examine them under conditions relevant to current and future spacecraft missions in the “Icy Worlds Simulation Laboratory” at JPL which contains several vacuum chamber systems that can replicate the surface ice conditions on ocean worlds including, specifically, those of Europa and Enceladus. The plume particles synthesized and analyzed in Tasks 6-1 to 6-3 will be non-destructively characterized, and serve as a ‘ground-truth’ for particles that may be detected on ocean worlds. Our process for translating measurements made on samples from Earth’s oceans to measurements that could be made on ocean worlds is as follows: each type of particle (fresh subsamples for each experiment) will be deposited as an optically thick coating of particles onto a gold or aluminum substrate that serves as the cold-finger target in Co-I Hand’s ‘Ocean World in a Can’ chamber (see: 9. Facilities & Resources). We will reduce the temperature and pressure within the chamber to pertinent ocean world surface pressures and temperatures (e.g. <1e-8 Torr; 100K to >180K for Europa and Enceladus) and collect baseline measurements of the sample using the in situ instruments attached to the chamber: visible, near-infrared, and mid- infrared spectrometers as well as a mass spectrometer. Ice coatings will be simulated by vapor depositing H2O on top of the grains, and spectroscopic measurements repeated to monitor modification of signatures as a function of water film thickness (ice can mask these signatures). We will then initiate high-energy electron irradiation of the sample under conditions that generate varying cumulative radiation exposures appropriate to simulating the variety of radiation environments predicted for different ocean worlds including, specifically, Europa and Enceladus (Paranicas et al., 2009; C.Paranicas, pers. comm., 2017). We will collect spectroscopic measurements as the experiments continue to monitor modification of signatures as a function of total dose. Those spectra will also be used to monitor for volatile production (e.g. destruction of organics to gas phase byproducts). At the end of each experiment, the sample will be warmed to room temperature at a programmed rate (e.g. 0.5 K per minute) while monitoring release of volatiles and modification of target materials. Finally, the sample will be stored in an inert gas headspace and returned to Co-I Toner for ‘post-cryogenic irradiation’

39 particle analysis. Those analyses will provide data at high spatial and spectral resolution for comparison to the mission-relevant spectrometer observations made in the “Icy Worlds Simulation Laboratory”. By conducting the experimental approach detailed above, we will be able to characterize and quantify the particle tracers under ocean world surface conditions with particular relevance to past and future missions to Enceladus and Europa. In so doing, especially for high-irradiation cases, such as are to be expected for Europa (NASA, 2017a), we will be able to carefully monitor the modification or destruction of organic particles, and we will be able to observe oxidation of materials that may arise from exposure to radiation or radicals produced from irradiation.

Figure 3.15 Schematic showing how particulate tracer characterization, (a) size, (b) morphology, and (c) composition, can be used to interpret ocean world conditions.

40 Particulate tracer interpretation. The project-wide characterization of particulate tracers summarized in Fig.3.14 will involve considerations of all of: (a) particle size, (b) particle morphology (surface shape and internal texture), and (c) particle composition (Fig.3.15). Particle size can provide information regarding transport potential from seafloor to ice-shell (Fig.3.15a). Nano-particles have high transport potential. In contrast, the detection of micro- particles may be consistent with one of several different scenarios: fast transport; low density allowing for longer transport time or routes; or formation in-situ at the ice-shell. External and intra-particle morphology can provide information on particle formation conditions (Fig.3.15b). Even certain external morphologies are diagnostic (e.g. salts are consistent with formation in situ). Considering individual particle grains in more detail, homogeneous intra-particle morphology is consistent with purely abiotic formation processes (organic or inorganic), while intra-particle heterogeneity suggests physical mixing of inorganic and organic inputs. When particle size and morphology are combined with particle composition, it is possible to infer ocean world conditions: redox status and the abiotic-biotic character of the underlying ocean (Fig.3.15c). For example, the chemical form of metals in particles can be diagnostic of prevailing redox conditions. Metal oxides are consistent with an oxidizing ocean. Metal sulfides could indicate an oxidizing or reducing ocean based on our knowledge of Earth, and could be evidence for hydrothermal activity. Metals precipitated in reduced form as salts would indicate a reducing ocean with metals delivered to the surface as solutes. The detection of organic particles would provide clues about the abiotic or biotic conditions. For example, micron-sized and heterogeneous particles having organic-inorganic components would be consistent with a biotic ocean based on our knowledge of Earth. The experiments conducted in this Investigation will create a library of particle tracer outcomes with which to define the sensitivity of tracers to potential interferences: an important tool in the evaluation of biosignature potential.

Overview Investigations 1-4 will provide us with the basis to assemble a coherent interdisciplinary understanding of how system-wide interactions among geophysical and geochemical processes on any given ocean world can give rise to its capacity to support and sustain life – its biological potential. By combining that research with the results of Investigations 5 and 6, we will be able to extend our work, and investigate the potential for an ocean world to yield detectable signals that provide evidence for life (or evidence of conditions suitable for life) at the point where they can be observed by spacecraft missions – its biosignature potential. While consideration of these phenomena will inform our research throughout the entire program, we will undertake two periods of particularly intense Synthesis Activity: (a) At the outset of the program we will conduct a thorough review of the current state of knowledge concerning biological potential, including consultation with the entire NAI community via a first dedicated Workshop Without Walls. The purpose of this initial synthesis will be two- fold: to ensure a thorough grounding for the theoretical framework that our team has developed during the formulation of this proposal and to complete a first “state of knowledge” review of what is known about the biological potential of ocean worlds for publication in the peer-reviewed literature. Completion of this initial synthesis phase will represent Milestone 1 of our overall program (see: 4. Science Management Plan; Table 4.2). (b) Following a period of intense activity across all six of our Investigations, our second milestone will be reached by the end of Y3 of the project. It is at that stage that we will have

41 completed population of our reaction-path data-base via a combination of Investigations 1-4 and will be ready to begin Phase 2 of our program. Thus, Milestone 2 will not only represent a period of achievement (completion of our Phase 1 modeling and experimental studies) but also a point of departure: 24 months before the end of the project, at the same time that we begin our Phase 2 modeling and experimental studies, we will also be ready to begin quantitative Synthesis Activities assessing biological potential and, informed by the new information to be obtained from Investigations 5 and 6, of biosignature potential. Biological Potential Our synthesis builds around assessing a system’s potential to generate and sustain biomass – the two basic functions into which life partitions resources. Considering end-member cases for this partitioning places upper bounds on cell abundance and the rate at which biologically- derived material enters the environment. McCollom (1999) estimated global bioavailable energy flux as the product, Jenergy = ESFF * JSFF, where ESFF is the mass-normalized energy content of reacted seafloor fluid upon mixing into a bulk ocean and JSFF is the global mass flux of that fluid. Recent works (Hand et al., 2009; Vance et al., 2016) have taken a similar approach, as we will also do. What distinguishes the work proposed here, however, is the manner in which ESFF and JSFF will be constrained.

ESFF . Previously, it has been necessary to make a variety of specific assumptions regarding starting compositions, reaction conditions, and fluid fluxes in order to define a computationally tractable scope. In this project, through access to the NASA High End Computing facility at Ames Research Center, Investigation 3 will quantify ESFF via millions of reaction path calculations that make very few assumptions regarding compositional inputs or reaction conditions ab initio, and only pare that space down through observational, experimental, and modeling constraints. Fluid energy content, ESFF, can be equated to biosynthetic yield (Heijnen & van Dijken, 1992; McCollom & Amend, 2005), and this constrains one aspect of biological potential: it places an upper limit on the fluid concentration of biologically-derived material, absent any destruction or the expenditure of energy on biological maintenance (Tijhuis et al. 1993; van Bodegom, 2007; Hoehler, 2004; Hoehler & Jørgensen, 2013).

JSFF . Informed by Investigation 1, Investigation 2 will evaluate how much fluid flows through what kinds of rocks, and under what conditions, with two important consequences for biological potential. First, it narrows the range of ESFF to a subset of the full range computed in Investigation 3, by restricting compositional inputs and reaction conditions to those consistent with geophysical constraints such as heat budget and planet size/density. Second, it allows for the calculation of energy flux (vs. standing energy content, ESFF). The resolution of the Investigation 2 modeling will determine JSFF as a distribution of mass fluxes partitioned into different physical systems and associated temperature ranges, rather than as a single term. To the extent that these fluxes have different chemical characteristics, the basic equation for energy flux can be recast as Jenergy = Σ (ESFF-Ti * JSFF-Ti), where JSFF-Ti is the fluid flux occurring within a given temperature range, Ti, and ESFF-Ti represents the energy content of fluids equilibrated within that temperature range. Determination of energy flux supports calculation of a second dimension of biological potential – the standing biomass that a given system can support (Tijhuis et al., 1993; van Bodegom, 2007; Hoehler, 2004; Hoehler & Jørgensen, 2013). This is critical not only for informing detection thresholds for spacecraft investigations that seek evidence of active life (cells), but also because energy flux devoted to cell maintenance reduces the energy partitioned into production of new biological material. We will calculate an upper limit on standing biomass, expressed as bulk volumetric cell abundance, initially using the temperature-dependent maintenance energy relations described by Tijhuis et al. (1993). Having established end-member (upper limit) cases for biosynthesis and cell maintenance, we can evaluate the impact of intermediate cases on

42 biosignature potential, by varying cell turnover times across a range of values that approximate those in relevant ecosystems on Earth. The empirical constraints provided by Investigation 4 factor critically into understanding both the geochemical supply and biological utilization of energy under conditions relevant for other worlds’ oceans. The determination of Jenergy, as it is described above, is based on equilibrium calculations that assume complete reaction. However, particularly for the relatively low temperatures that may comprise a significant fraction of total fluid flux (Stein & Stein, 1994; Mottl, 2003), it becomes essential to consider the kinetics of fluid-rock reaction: assuming equilibrium where it is, instead, incomplete or metastable would lead to over-estimation of energy flux, and thus of biological potential. Published work provides some constraints on the kinetics of water rock reaction at lower temperatures (McCollom et al., 2016 and references therein) but Investigation 4 will provide these constraints for compositions and conditions identified in Investigation 3 as specifically relevant to this study. Empirical constraints will also inform how the biological utilization of energy is parameterized in estimating biological potential. In particular, while biosynthetic yields across a wide range of cultured organisms are captured well by the thermodynamic parameterization of Heijnen & van Dijken (1992), maintenance energy yields measured in cultures of typical model organisms (Tijhuis et al., 1993) may significantly exceed the apparent requirements of organisms in low-energy natural systems. The maintenance/yield constraints provided by Investigation 4, for relevant metabolisms under relevant environmental conditions, will improve the accuracy of our biomass abundance estimates.

Biosignature Potential Investigations 1-4 focus around the potential for seafloor fluid flow and mixing to deliver energy that can fuel biological activity at and close to the rocky seafloor of an ocean world. This provides the basis and the theoretical framework from which we can predict an ocean world’s biological potential. However, it is quite conceivable, a priori, that an ocean world could be both habitable and inhabited (high biological potential) yet evidence for life on that world might still evade detection (low biosignature potential). Consider the case, for example, of an ocean world teeming with life but with no mechanisms by which diagnostic evidence for life is transported to the planetary exterior. This is why Investigations 5 and 6 are essential. In NASA’s continuing search for life, all currently funded or proposed ocean world missions are predicated on an ability to detect evidence of life and/or of conditions suitable for life at the exterior of an ocean world. Accordingly, in this synthesis activity, we seek to provide the scientific basis for interpreting any such observations, and their significance, with confidence. The biosignature potential, for any given ocean world will be governed not just by the creation of specific biogenic features, but also by their transport, modification, and destruction. This balance of factors defines a residence time, τi = [i]/Ji , where [i] and Ji, are the concentration and flux, respectively of a constituent, i. Residence time can be thought of as the time scale required for accumulation to a given concentration, or the average time a particular species or tracer spends in a pool of specified concentration before consumption and/or destruction. In our study, Investigation 5 will quantify how rapidly any evidence of life, or of conditions suitable for life, is delivered from its point of origin to a point where it can be observed. The extent to which any (bio)signature might be altered during transport, for any given tracer type (i.e. how detectable or diagnostic it would be by the time it reaches that point of observation) will be explored in Investigation 6.

43 The residence time relationship is a key concept in ocean system science and will be central to our approach. It relates the concentration of a specific analytical target – a direct measure of detectability – to the processes and time scales that govern its cycling. In this activity we will begin by creating relatively simple box models to integrate constraints on Figure 3.16 Example of a simple box model used to the ocean circulation gained from investigate coupled cycling of Fe and organic carbon Investigation 5 with information on associated with submarine venting ant its impact on Earth’s rates for formation and destruction global biogeochemical cycles (German et al., 2015). of key particle-bound tracers (Investigation 6). Even such a relatively modest conceptual approach can be extremely powerful. In recent work, German et al. (2015) used a 7-box model (Fig.3.16) to investigate the coupled cycling of Fe and organic C in deep sea hydrothermal systems and their impacts on Earth’s ocean biogeochemical cycles. That study yielded two important predictions relevant to ocean worlds: (1) Fe-stimulated productivity in the deep ocean can be sufficient to drive a particulate organic flux to Earth’s deep ocean floor that is significant, even on a planet that hosts photosynthesis. (2) the dominant driver of this biogeochemical cycle arises from low-temperature hydrothermal flux, not the visually more spectacular high-temperature fluid flow. Co-I Thurnherr has extensive experience in creating similar, directly relevant, numerical codes for a range of interdisciplinary oceanographic applications (Thurnherr, 2000, 2006; Hardy et al., 2015). He and PI German have also worked successfully together, previously, to develop a first interdisciplinary approach to quantify physical and biogeochemical export fluxes from a seafloor vent-site to the ocean (German et al., 2010). Here, we will adapt the same approach outlined, above, for assessing biological potential. During Phase 1 of the project we will look forward to working with the rest of our team and the wider NAI community and using our experience in studying Earth’s ocean system to develop an appropriate conceptual model for tracer transport and (bio)geochemical reactivity in the oceans of ocean worlds. In Phase 2, once results become available, we will use the inputs and constraints provided from Investigations 5 and 6, coupled with access to NASA’s High End Computing facility, to investigate, on a tracer by tracer basis, which (bio)geochemical tracers would be the most powerful to analyze across the full array of ocean circulation scenarios considered, including the survivability of those tracers under different radiation environments once they are expressed onto an ocean world’s surface.

Concluding Remarks Completion of our Synthesis Activities will allow us to meet our two key objectives. By considering ocean worlds at the systems level, connecting all the way from geophysical underpinning to biological potential, we will have established a new theoretical framework with which to consider which ocean worlds, with which physico-chemical properties have the greatest potential to host and sustain life. By introducing considerations of physical and (bio)geochemical cycling within the oceans of ocean worlds we will, additionally, provide a new theoretical framework to predict which ocean worlds are most likely to yield evidence of any such life, where that evidence is most likely to be found, and which combinations of measurements would be most powerful to detect it.

44 4. Science Management 4.1 Project Structure This project will be led by PI German who will be responsible for the quality and direction of the entire investigation and for the use of all awarded funds. German has a long and successful track record leading complex interdisciplinary programs (see PI curriculum vitae). A four-person Executive Committee (ExCom), drawn from the Co-I team, will advise the PI, help integrate research, and coordinate education, outreach, mentoring, and data management activities across the project. Membership of ExCom will be on a staggered rotating basis (nominal 2 yr term) with members selected to ensure balance and representation across the team membership (e.g. geo- and life scientists; ocean and planetary scientists). Initially, the ExCom will comprise Co-Is Blackman (UCSD), Girguis (Harvard), Hand (NASA-JPL), and Hoehler (NASA-Ames). At WHOI, German will be supported by Project Manager Kim Deisher (who has interacted with the team throughout the preparation of this proposal and will continue to coordinate all meetings and oversee budgets), Multimedia Specialist Matt Barton (Electronic Communications & Collaboration; he will also represent the team on NAI Central’s IT Working Group) and Science Writer/Web Editor Ken Kostel (WHOI Communications). 4.2 Roles and Responsibilities: An Integrated Matrix for Interdisciplinary Research Research conducted within the program will be structured as a matrix of science investigations (Table 4.1). Each Co-I has an active role to play in multiple investigations, reflecting the interconnected nature of the systems-wide approach that we will employ (Fig. 3.2). This is why the depth of each participant’s experience was a critical criterion during our selection of the team’s membership. Importantly, our team of theorists and experimentalists also boasts a wealth of experience in field-based research, on Earth and in Space. This will help to inform the laboratory work to be performed in this project and to ensure that recommendations arising from this research can be readily implemented: from technology development for future space missions to undertaking oceanographic missions most appropriate for Earth analog research.

Each Investigation will be conducted by a team of multiple Co-Is with one or more scientific leads: the precise blend of expertise has been selected, in each case, according to that investigation’s interdisciplinary research priorities, hence, intellectual needs.

45 The PI, supported by ExCom, will ensure that each Investigation’s work is progressing, that connections between Investigations are rich, allowing interactions to flourish, and that the team maintains a culture of nurturing cross-disciplinary learning, critical thinking, and collaboration. PI German (0.27 FTE) is an expert in leading interdisciplinary ocean and astrobiology science teams to explore for and characterize novel and diverse forms of seafloor fluid flow. He will lead the program as a whole and use his breadth of experience to contribute to all of Investigations 1-6 and to co-lead the Synthesis. He will look forward to participation on NAI Executive Council. Co-I Blackman (0.10 FTE; PhD student) is a marine geophysicist with broad observational and modeling expertise. She will serve on the initial ExCom, co-lead Investigation 1, and also contribute to Investigations 2, 5 and the Synthesis Activities. Co-I Fisher (0.12 FTE; PhD student) is a marine hydrogeologist, expert in numerical modeling of coupled flows across a range of spatial and temporal scales. He will lead Investigation 2 and also contribute to Investigations 1, 3, 4, 5 and the Synthesis Activities. Co-I Girguis (0.24 FTE; 2 x 2y Post-Doc) develops novel techniques to study marine metabolic processes. He will serve as part of the initial ExCom, lead large-volume experiments in Investigations 4 & 6, and contribute to Investigation 3 and the Synthesis Activities. He will act as liaison for Collaborator Roberson (see below). Co-I Hand (0.14 FTE; 2y Post-Doc) is an expert on the geochemical cycling of ocean worlds. He will serve on the initial ExCom, co-lead Investigation 6 with prime responsibility for surface process studies and contribute to Investigations 3, 4, 5 and the Synthesis Activities. Co-I Hoehler (0.10 FTE; 2y Post-Doc) is an expert in adapting principles of ocean biogeochemistry so that they can be applied to ocean world astrobiology. He will serve on the initial ExCom, co-lead Investigation 3 and the Synthesis Activities, and contribute to Investigations 2, 4, 5 & 6. He will oversee ingestion of all data into the AHED database at Ames. Co-I Huber (0.18 FTE) is a marine microbial ecologist with wide experience of diverse chemosynthetic ecosystems. She will lead all microbial experiments as co-lead of Investigations 4 and 6 and also contribute to Investigation 3 and the Synthesis Activities. Co-I Marshall (0.12 FTE; 2 x 2y Post-Doc) is an authority on 3-D modelling of planetary scale ocean circulation on Earth (both past and present). He will co-lead Investigation 5 and contribute to Investigations 1, 2, 6 and the Synthesis Activities. Co-I Seewald (0.20 FTE; PhD student) has extensive field, laboratory and theoretical experience studying the geochemistry of fluid-rock reactions. He will lead abiotic experimental work in Investigation 4 and also contribute to Investigations 3 and 6 and the Synthesis Activities. Co-I Sotin (0.10 FTE) is an expert in the geophysics of ocean worlds in the outer solar system including the interior structure and tidal heating of Europa and Enceladus. He will co-lead Investigation 1 and contribute to Investigation 2 and the Synthesis Activities. Co-I Shock (0.04 FTE; PhD student) is an expert in predicting how planets can support life using field work, experiments and theory across multiple disciplines. He will co-lead Investigation 3 and contribute to Investigations 2, 4, 6 and the Synthesis Activities. Co-I Thurnherr (0.10 FTE) has particular expertise in applying knowledge gained from studying the physics of deep ocean circulation to interdisciplinary research projects. He will co-lead Investigation 5 and the Synthesis Activities and also contribute to Investigations 1, 2 and 6. Co-I Toner (0.12 FTE, PhD student) is an aqueous geochemist with particular expertise in the grain by grain analysis of (bio)geochemical particles. She will co-lead all aspects of Investigation 6 and will contribute to Investigations 3, 4 and 5 and the Synthesis Activities. Collaborator Roberson is President of Roxbury Community College (RCC), a recognized Minority Institution. Our project will award RCC’s students a total of five competed three-month research project placements among our team’s laboratories (physics, modeling, microbiology).

46 4.3 Project Plan, including anticipated Milestones (see next page) Within each Investigation, we have identified a series of Tasks and a timeline for completion of each, which are presented in Table 4.2 on a quarterly basis. Completion of Tasks and combinations of Tasks will lead to a series of project-wide Milestones, described below. In addition, we have also identified a series of key top-level Activities to ensure that (a) communication and collaboration are sustained internally throughout the duration of the five- year period of performance (see following section) and (b) our project remains closely tethered to the work of the wider NAI community. Prominent among these Activities will be three NAI Workshops Without Walls, in which we will engage with the widest possible intellectual “gene pool” interested in ocean world exploration, as drawn from the astrobiology and ocean science communities. Co-I Hoehler has directly relevant recent experience in organizing and leading the WWW on “Serpentinizing System Science” as part of the NAI CAN7 RPL team, and will bring that experience to the organization of the workshops planned here. As discussed elsewhere (see 7. Other Institute Objectives), PI German has extensive complementary experience in the use of telecommunications for remote interactions. In Year 1 we will present, and seek feedback on, the initial plan for activities presented in this proposal, as an integral part of the first Synthesis activity. In so doing, we will ensure that the expertise and inputs of the broader community are fully considered as we develop a conceptual framework for assessing biological and biosignature potential. In Year 3 we plan to organize a second WWW meeting, following the same partnership with NAI. While this will be an opportunity to provide a community-wide update on our research, the primary motivation for this workshop will be to capture new, relevant developments from the broader community and solicit feedback on research activities and priorities planned for the second half of the project performance period. This is essential to ensure that “course corrections” (as needed) are informed by emerging research findings, both from within our team and from the broader astrobiology, planetary, and ocean sciences communities. Of course, we will not be conducting our research in isolation in between the NAI WWW meetings. We will continue to participate in other relevant national and international meetings including, prominently, active participation of the entire team in the Astrobiology Science Conference meetings that are scheduled for Y2 and Y4 of the CAN 8 cycle. We anticipate that Ocean Worlds will continue to be a prominent and pervasive theme in both meetings. Finally, in Y5, we will plan a final Workshop Without Walls in partnership with NAI, to capture the intellectual state of knowledge as this project approaches completion. A specific emphasis will be on aspects of our findings that can help provide recommendations for near- and longer-term technology development and Earth-analog field research. Project-wide Milestones: We anticipate four major team-wide milestones within this project: MS#1 (Y2, Q1-2) Refinement of the conceptual theoretical framework for our study, drawing on new information from: preliminary tasks conducted in each of Investigations 1-6; team-wide interactions (Y1, Y2 meetings); and community input from the Y1 WWW discussions. Expected outcomes: presentation of our deliberations to AbSciCon; publication of a “State of Knowledge” peer-reviewed journal article on assessing ocean world biological and biosignature potential. MS#2 (Y3, Q4) Completion of Phase 1 modelling and experimental tasks across Investigations. Expected outcomes: Feedback between teams to inform Phase 2 modeling and experiments. Community-wide consultation via Y3 WWW to inform any Phase 2 course corrections. Reaction path data base complete. Begin quantitative Synthesis; teach “Ocean Worlds” graduate seminar. MS#3 (Y5, Q2) Completion of all Phase 2 modelling and experimental tasks. Expected outcomes: Present results to NAI community via Y5 WWW and discuss emerging recommendations including those from Phase 2 Synthesis Activities. MS#4 (Y5, Q4) Completion of all Synthesis Activities. Report out conclusions of project as a whole, including recommendations to NASA for future ocean world exploration missions.

48 4.4 Within-Project Communication A key to the success of this project will be regular and effective communications within our team to ensure the level of cross-investigation coordination required for a true ocean system approach. We recognize that this aspect of our work will be challenging, given a geographically distributed team and the scientifically diverse methodologies we will bring to bear, but PI German has extensive experience in ensuring exactly this sort of coordination in projects of this scale. We will achieve this coordination through a nested communications approach that consists of bi-weekly 30-minute meetings within the ExCom (for project management) and monthly 90-minute meetings of the entire Science Team. The latter will include both time for tag- up and communicating out news from across NAI (e.g. from PI German’s participation in NAI Executive Council) and a formal research summary from one of the Co-Is (this role will rotate among the Investigations, with each Investigation presenting twice per year). We will conduct these meetings via video-conferencing using Zoom.us, which has been utilized effectively for a diverse range of telepresence applications in ocean research, as well as for the communications within at least one NAI CAN7 team. We also plan annual face-to-face team meetings, separate from the national/international meetings discussed above, to ensure that ample time is available for integrating new results and fully coordinating research efforts going forward. These will also offer important venues for our early career scientists (5 PhD students and 2-3 post-docs at each meeting) to present the newest results emerging from their research. We will host the first of these meetings at WHOI, with subsequent meetings alternating between East and West Coast, Ocean Science and NASA laboratories: Ames, Harvard & JPL. The final team meeting will be held in the vicinity of Kennedy Space Center, to coincide with the launch of the Europa Clipper mission.

4.5 Cost Analysis Throughout the development of this project and especially its research scope and associated budget, we have maintained a sharp focus on what is achievable and realistic, while doing the most to accelerate the pace of discovery in ocean worlds science. Ocean-based fieldwork is expensive, and space missions far more expensive still. Our intent here, therefore, is to add significant context and direction to these endeavours at modest additional cost, with an approach built around theoretical modelling and complemented by carefully selected laboratory experiments. Importantly, this approach builds heavily on the prior modelling work of various Co-I’s for their work in ocean and planetary sciences, and therefore heavily leverages powerful existing codes that have taken extensive efforts to develop (see 9. Facilities & Resources). Here, time and funds will be spent to adapt and integrate these models, rather than develop them from scratch. We envision this deliberative approach to be the most cost effective and expeditious path by which our NAI CAN8 team could produce findings that bear meaningfully on ocean worlds missions, informed by Earth ocean analog research. Our detailed project plan (Table 4.2) shows that our goals are achievable and our long experience, drawing upon the nationally and internationally recognized expertise working within each of our Investigations and Tasks, reassures us that what is proposed here fits well to what can be delivered within this schedule and budget. Our budget, in turn, fits well to the projected resources discussed in the CAN8 briefing and call (Anticipated $9-10M/yr among 5-7 NAI Teams). Funds will be distributed across the project in a deliberate effort to maximize the participation of students and postdoctoral researchers, while still ensuring that the expertise of senior investigators is fully brought to bear. Specifically, the project would cumulatively support 7.5 years of research among our cohort of international experts, together with 12 years’ research effort from postdoctoral investigators and the training of 5 interdisciplinary PhD students.

49 5. Data and Sample Management Plan

5.1 Overview: Ocean World Data Management for Astrobiology and Ocean Sciences This Data and Sample Management Plan meets and exceeds the requirements set out in the NASA Plan for Increasing Access to the Results of Scientific Research (NASA, 2014b). As such, PI German and Co-I Hoehler will lead the team’s effort to ensure that all information is disseminated widely throughout the astrobiology and ocean science research communities. To that end, we have developed a four-component approach to data and sample management that ensures both complete and efficient access to all materials: First, at the beginning of the program, we will establish a web-based data portal on our NAI team’s internet home-page. Members of the team and broader public will be able to access all processed data that has been through the appropriate quality assurance/quality control (QA/QC). Second, throughout the lifetime of this NAI, we will bank copies of all raw and QA/QC processed data products in dedicated open-access repositories that are commonly used by ocean and space science researchers (see below) Third, we will deposit complete sets of our data products to the emergent Astrobiology Habitable Environments Database (AHED) hosted at the NASA Advanced Supercomputing Division (NAS) at NASA Ames. Research associate Som (a member of Co-I Hoehler’s team) has been involved in the development of this database and will be responsible for developing the mechanisms that will ingest our data products into AHED. An important and obvious opportunity arising from this project is that, from its outset, templates for all future Ocean World data assimilation within AHED can be informed by best data-management practices already established through over a decade of effort conducted under NSF’s Division of Ocean Sciences. Fourth, while physical objects are not typically considered in this context, we have established a pilot program with the Ocean Genome Legacy to develop a deposition and archiving system for experimental products of astrobiologically-relevant experiments.

5.2 Digital Data Source code: As specified by NASA, “any and all source code developed within this NAI, with associated documentation sufficient to enable the code’s use, will be made publicly available via GitHub (https://github.com/NASA-Planetary-Science)”. At this time, the volumes of such source code are unclear, but it will likely not be in excess of 1 GB. Rocky Interior, Sub-seafloor Hydrogeology and Ocean circulation model data: Interior convection simulation outputs, with run parameters, and results of 1-D and 2-D geophysical modeling will be archived (~10 GB total) in the Marine Geoscience Data System within Interdisciplinary Earth Data Alliance (IEDA; www.marine-geo.org/). The IEDA is extremely robust and funded long-term by NSF, ensuring long-term data preservation, discovery and dissemination. Sub-seafloor fluid circulation data types include ASCII input and output files for coupled simulations, formatted for FEHM (primary numerical simulator; Zyvoloski, et al, 2011) and for post-processing with Paraview and Matlab. Each large simulation (500k to 1M nodes) generates up to 1 GB. These data will be deposited in the National Centers for Environmental Information (www.ncei.noaa.gov). Co-Is generating ocean circulation models will follow current practices, archiving outputs in Dataverse (www.dataverse.org/), an open source web application to share, preserve, cite, explore, and analyze research data. The Dataverse indexing system will be used in conjunction with bulk storage resources purchased from the regional Northeast Storage Exchange (NESE - http://projectnese.org), which is budgeted to cover an expected 75 TB for a 6-yr term coinciding with this project. Ultimate retention as archived material will emphasize outputs, and associated run parameters, related to published results and selected outputs with long term value.

50 Geochemical, biogeochemical and microbiological phenotypic data: Geochemical data, including but not limited to water chemistry data, X-ray absorption spectra, X-ray and electron diffractograms, X-ray and electron microscopy images, will be submitted to IEDA, and in many cases specifically to the EarthChem (www.earthchem.org/) division of the database. EarthChem, in particular, is configured to allow easy, searchable access to chemical and geochemical data. Biological data, including but not limited to strain information, media information, experimental contextual data, physiological data such as metabolic and growth rates, and other similar data will be available in ASCII, .xls, or .fasta file format. Past experience indicates that these data will total less than 10 GB. They will be deposited in the Biological and Chemical Oceanography – Data Management Office (BCO-DMO; www.bco-dmo.org). This NSF-funded facility is tailored to host biogeochemical and microbiological data that does not readily fit into other repositories. When appropriate, any DNA, RNA or protein sequence data will be made publicly available through the genome repositories GenBank (NCBI) and the Small Read Archive (SRA).

5.3 Policies for Data Access and Sharing All team members will be required to submit their raw and processed data to the appropriate database (e.g. MGDS) as soon as available, and no later than 12 months after data acquisition. These data will be available to the entire NAI team through a password-protected data portal, ensuring that all team members have an opportunity to easily share and exchange data while further protecting said data from accidental loss. Second, all team members will be required to make their raw and QA/QC’d data fully public within 24 months of acquisition. When appropriate, such as when protecting a student’s dissertation, we will seek permission for a six- month extension to 30 months. Finally, without exception, all data products will be shared with the public domain -in entirety- no later than 12 months after the conclusion of this effort. Monitoring the progress of this data deposition and dissemination will be the primary task of a member of the coordination team. This task will be assigned to Co-I Hoehler initially, but may be re-assigned each year per the coordination team’s suggestions. Decisions on data management best practices, however, will be made by the entire team (with input from NAI Central whenever appropriate) during our annual in-person meetings.

5.4 Long-term Physical Sample Repository Physical samples arising from any project are of great value in allowing corroboration of our assessments by independent investigators, as well as enabling future analyses using other techniques. Accordingly, all physical samples generated through laboratory experiments by the relevant Co-Is of this program will be submitted to the Ocean Genome Legacy (www.northeastern.edu/ogl/), a non-profit foundation tailored to archive tissues and genomic material of marine animals. In collaboration with director Dr. Dan Distel, we will adopt his highly successful database to accommodate all our biological samples, as well as abiotic synthesis products. We will send all physical samples to him for archiving at -80°C. The objective is to assess the efficacy of such long-term archiving, and to discuss among the team and the broader community whether such efforts facilitate the exchange of materials for cross-lab comparisons. Of course, all samples will also be preserved long-term in individual Co-Is archives and will be available for access. A complete inventory of samples will be maintained on the dedicated web- pages to be established that will form part of our NAI team’s web-presence beyond the lifetime of this project (www.whoi.edu/exploringoceanworlds).

51 Table of data type, attributes, and target repositories

Repository Repository Repository Data type Format Volume #1 #2 #3 Investigator Source code Text <1 GB GitHub institutions Convection National Astrobiology simulation Interdisciplinary Centers for Habitable outputs, results ASCII, Earth Data ~10 GB Environmental Environments of 1-D & 2-D FEHM Alliance Information Database geophysical (IEDA) (NCEI) (AHED) models Astrobiology Ocean Northeast Habitable Up to Storage Circulation ASCII Dataverse Environments 75 TB Exchange models Database (NESE) (AHED) Marine Astrobiology Geochemical, Geoscience Habitable mineralogical ASCII, .xlsx <10 GB EarthChem Data System Environments data (MGDS) Database (IEDA) (AHED)

Biological and Astrobiology Chemical GenBank Habitable Oceanography - Small Read Biological data .xlsx, .tiff, <10 GB Environments Data Management Archive (SRA) Database Office (AHED) (BCO-DMO)

Physical Ocean Genome Material Investigator sample N/A Legacy samples institutions repository (OGL)

Table summarizing the data products and the repositories in which they will be deposited. Note that all data products will be accessible via the NAI’s “Exploring Ocean Worlds” website (www.whoi.edu/exploringoceanworlds), where a dedicated data page will link to repositories.

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72 7. Other Institute Objectives

7.1 Community and Collaboration The PI and our entire team are excited to engage in, and contribute actively to, the objectives of the NAI as a collaborative consortium. As a team rich in ocean science expertise, we believe that we have much to contribute to the astrobiology community and, in turn, much that we can learn and communicate outward to the wider oceanographic community. Importantly, in keeping with the ethos of astrobiology, we have been trained in the pursuit of interdisciplinary research to investigate Earth-Ocean-Life interconnections throughout our professional careers. We enjoy a shared vision and are well placed for fruitful and meaningful collaboration. The PI and ExCom team for Exploring Ocean Worlds, in particular, feel that we will have valuable contributions to bring to the functioning of the NAI Executive Council and our interactions with NAI Central and its Director. Of the three specific roles of the Executive Council, we believe that we will be especially well placed to help (i) share our expertise in the use of telepresence to conduct real-time collaborative field programs using a single remote asset and a distributed network of science Co-Is (Section 7.5); (ii) develop a new graduate student level course on Ocean World Astrobiology for NAI (see section 7.2) and (iii) catalyze new conversations between NASA and other agencies and private institutions pertinent to Ocean World investigations (Section 8.3). In addition to our team’s long track record in leadership of national and international deep ocean research programs, PI German is currently a member of the advisory board for NOAA’s Ocean Exploration and Research program and Co-I Blackman has recently returned to research from a 3 year rotation as a program officer for NSF’s Division of Ocean Sciences. Among private foundations, Co-I Girguis advises the Ocean Exploration Trust, and PI German enjoys strong relationships with the Schmidt Ocean Institute and the Dalio Fund for Ocean Exploration (ship operations managed at WHOI). All share a passion to advance the use of novel technologies in ocean world exploration. Key to building a community is an effective use of collaborative communications tools. As researchers who have pioneered the use of telepresence for deep ocean investigations (see section 7.5) we stand ready to contribute, share, and learn from current best practices already enjoyed within the NAI community. We are particularly excited about the opportunity to make meaningful use of the Workshops Without Walls, which NAI has implemented, as a cornerstone of our proposed program of work. Co-I Hoehler already organized and led a WWW activity on serpentinizing systems, and brings this directly relevant experience to our team. As described in our project plan (Section 4.3) we will make use of this capability across the span of our program, not just to share our own ideas, but to actively solicit feedback from the NAI community and ensure that the work we undertake remains closely tethered to both the collective knowledge and the anticipated future needs of the wider astrobiology community. We will, of course, be keen to contribute to and participate in all NAI activities including the Director’s seminar series and the bi-annual Astrobiology Science Conference which our entire team will attend and contribute to. In Phase 2 of our program we also propose a formal semester-long graduate-level “Ocean Worlds” course, building from an already established base at WHOI, that we would make accessible to the entire NAI community (Section 7.2). A further ambition of this team’s proposal would be to not just broaden but also deepen collaboration within the existing NAI community. Our team is extremely well placed to bridge between, and build out collaboratively from, the work already being undertaken by two teams, in particular: Rock Powered Life (RPL) led from U.Colorado and Icy Worlds led from NASA-JPL. Indeed, much of the content and approach specific to this proposal arose directly from conversations between members from those teams during face-to-face meetings of the Europa Lander Science Definition Team (EL-SDT) in Summer 2016. Those conversations focused on what was missing, intellectually, from the NAI community’s collective knowledge base for future ocean world investigations. While not the specific focus of the EL-SDT deliberations, those

73 opportunities did present an opportunity for the PI of this proposal to build new and positive working relationships with RPL PI Alexis Templeton and Icy Worlds Co-I Mike Russell. In particular, our conversations highlighted the need to entrain more Earth oceanography expertise in developing strategies for ocean world exploration, and this significantly shaped the scope of the proposed work and the membership of our team. For example, the Rock Powered Life program is focussed primarily on the potential to support life through water-rock interactions with a specific interest in serpentinization reactions. That team is organized around two themes: one is focussed on a series of three major field- study sites, two on land and one at sea, that have an emphasis on low-temperature serpentinization; the other is focussed upon a series of complementary experimental and theoretical modelling studies of low-temperature reaction pathways. In this proposal, where theoretical considerations of the functioning of ocean worlds as potential abodes for life is more prominent, Co-I’s Shock and Hoehler, who are already active members of RPL, will take advantage of NASA’s High End Computing capabilities to vastly expand the range of conditions currently under consideration within RPL and then use those outcomes to help target the research directions of the laboratory experiments to be conducted in this work. Because the Co- Is involved in our experimental investigations (Seewald, Girguis, Huber, Toner, Hand) are already intimately familiar with so many of their counterparts within RPL, we will be able not only to ensure that there is no duplication of effort in what we undertake, but also to share results collected to common standards and using shared protocols. The Icy Worlds program has four key investigations. By design, our approach has been to recruit a team with expertise that is complementary to that team and, given the wide absences in our current State of Knowledge for ocean worlds, a complementary set of Investigations. For example, we plan no research focus on the emergence of metabolisms (Icy Moons Investigation 1) nor with associated experiments focussed on chemical gardens and green-rust catalysed reactions undertaken in their Investigation 2. Likewise, we do not propose any research on the processes that cause evolution of ocean signatures as they are transported through an ice shell and are expressed into the vacuum of space. Rather, we keep to our primary areas of expertise – everything that can occur within an ocean up to delivery of any potential evidence for life (or conditions suitable to sustain life) as far as the base of an icy moon’s outer shell, coupled with investigation of the same materials, on a like-for-like basis, after arrival at an ocean world’s exterior. Collectively, our teams’ efforts will provide new insights on the whole trajectory. Where our team has maximum potential for collaboration, however, is with the Icy Worlds Investigation III where our Co-I’s Sotin, Hand and Marshall already have strong collaborations. Sotin is a Co-I on both proposals; his emphasis in Icy Worlds, in collaboration with Icy Worlds Co-I Vance (JPL), is on convection within ice shells. By contrast, his role in our Exploring Ocean Worlds program is primarily focussed on the solid interior processes of ocean worlds, beneath the seafloor. Co-I Hand has recently co-authored a pioneering first paper with Vance investigating the potential to use geophysical considerations to investigate the geochemical compositions of ocean worlds’ oceans. Our Investigations 1, 2 and 3 will expand the theoretical basis for such work considerably, building out from that base, to be followed with dedicated experimental investigations to test those theoretical models (Investigations 4 and 6). Finally, Icy Worlds Co-Is Goodman and Vance have also been developing 1-D models for ocean circulation within the same Icy Worlds investigation. In our proposed work, Co-I Marshall who has collaborated with Goodman for more than 20 years, will build on that work and expand into 2-D and 3-D modelling of the same processes using the state-of-the-art MITgcm global circulation model (Investigation 5). Our team will then integrate those outcomes with studies of the evolution of (bio)geochemical signatures within those ocean pathways (Investigation 6) and also share our new model outputs with the Icy Worlds team.

74 7.2 Training Our program will train a new cohort of five PhD students and six 2-year post-doctoral researchers over the course of the program. We will also seek to enhance the formal training activities that we can offer through participation in the NASA Astrobiology Post-Doctoral Fellows program and through recruitment to other fellowships and scholarships offered among our home institutions. Further, because the majority of the early career researchers contributing directly to this program will be conducting astrobiological research in laboratories where they will be interacting with peers focused on Earth-based oceanographic research, the reach of our program outward into the next generation of interdisciplinary research scientists will be much greater than just those funded directly through this program. From a formal training perspective, a highlight of our program will be the development of a semester-long class designed primarily for graduate students, which will be taught during Phase II of our proposal. The course will build on WHOI’s Geodynamics Seminar Series, established in 2001 and taught annually ever since: an integrated program that fosters interdisciplinary research in geo- and life sciences among graduate students, post-doctoral fellows and faculty. Each year, the course is offered as a spring seminar series that focuses around a common theme from the perspective of a wide variety of different disciplines. The program has consistently attracted a broad array of international speakers to participate (http://www.whoi.edu/programs/geodynamics/). As indicated in Table 4.2 we will plan to develop this course during Phase 1 of the program and then seek to offer the course (“Searching for Life on Ocean Worlds”) in the Spring Semester of 2021, at the outset of Y4 of our program. While the format of the Geodynamics Seminar Series is to invite each speaker to visit WHOI and interact with students and post-docs for 2-3 days, the program has always live-streamed the flagship 2h weekly seminar given by each speaker to MIT so that graduate students and faculty there can also participate actively through live Q&A discussions. It would be trivial, technologically, to expand that access more widely to the entire NAI community. More importantly, we would be keen to expand the reach of this course, both in planning and content, beyond the host institution at WHOI through partnership with our team members, NAI Central and the PIs of the other NAI teams. At WHOI, a final aspect of the Geodynamic Seminar Series has been that it culminates with a study tour to visit critical field locations related to each year’s central theme. Again, we would be interested to work with NAI Central and the Executive Council to explore the possibility to expand the reach of such an activity. The Geodynamics Seminar Series at WHOI is funded independently and would be offered at no cost to this proposal. Upon successful completion it would, we anticipate, be beneficial to capture the materials so that variations of the same course could be taught again in future years, beyond the lifetime of our NAI CAN 8 proposed work. One way to ensure that would be through publication of a graduate-student level text. Both PI German and Co-I Blackman have relevant past experience, here, having previously served as lead editor for AGU Geophysical Monographs that captured the outcomes from RIDGE and InterRidge Theoretical Institute activities. Specifically, those monographs explored the interdisciplinary intellectual space between geophysicists and ocean scientists studying seafloor spreading centers and submarine venting (Phipps Morgan et al., 1992; German et al., 2004).

7.3 Engagement and Collaboration with Minority Institutions Women, minorities, and people from impoverished communities are woefully underrepresented within astronomy, astrophysics and the ocean sciences (Stassun, 2003; Holbrook, 2012; Gilligan et al, 2007). Promoting and sustaining diversity among these scientific communities is a critical aspect of advancing science, as studies have shown that diverse groups of problem solvers are far better at accomplishing their tasks (Page, 2008). Fostering and maintaining strong, diverse scientific communities in these and other disciplines is essential

75 to ensuring that US investigators continue to play a major role in advancing scientific discovery and technological innovation in the coming years. There is mounting evidence that developing and sustaining more diverse scientific communities is enhanced by providing opportunities for under-represented groups to participate in postgraduate-level research, and by increasing access to mentors that can facilitate networking opportunities and job placement in target scientific areas. Our team will work with Roxbury Community College - a Boston-based minority serving institution - to provide paid research opportunities for students from underrepresented groups to participate directly in our research, and to provide continued mentoring and assistance in job placement for those who become interested in working in astrobiology, ocean or space science. Roxbury Community College (RCC) is a co-educational public institution of higher education. RCC's primary objective is to provide its students an opportunity to access a college education that is aligned with their interests and aptitudes, while also reducing the economic, social, and academic barriers to such educational opportunities. Founded in 1973, RCC is an inclusive, multicultural, student-centered, urban community college. Its newly remodeled 16- acre, 6 building campus includes state-of-the-art science and computer laboratories, and is equipped with the latest in molecular biological instrumentation (Fig.7.1) and computational facilities.

Figure 7.1 Roxbury Community College faculty teach courses in advanced molecular biology and biotechnology. Notably, RCC is a lead community college in the Achieving the Dream™ (http://achievingthedream.org), program which is an ongoing national initiative to help community college students, (especially low income students and students of color who have traditionally faced the most significant barriers) to succeed, post-graduation. Through this

76 program, RCC works to increase the percentage of students who complete coursework, advance through programs, and earn certificates and degrees. To gauge the efficacy of their efforts, RCC documents over time the percentage of students who (1) successfully complete the requisite coursework courses with a grade of C or higher; (2) enroll from one semester to the next; and (3) certificates and degrees. Ultimately, through this initiative RCC seeks to help more students achieve their individual goals, which may include obtaining a better job, earning a community college certificate or degree and/or attaining a bachelor’s degree. We intend to offer RCC students the opportunity to work with our team of investigators directly, to be exposed to the latest ideas and technologies in ocean and space science, and to have access to mentoring and advocacy by leaders in these areas. We are excited to work with RCC on this program, as we have an opportunity to make an exciting and substantive impact on the lives of students who, otherwise, would not likely consider pursuing a career in science. This joint effort leverages heavily off the outreach programs developed by many members of our NAI team (Co-I’s Girguis, Huber and Toner have among them developed high-school student and teacher internship programs, community college internship programs, and URM summer bootcamps). We will also leverage heavily off the framework and assessment programs that RCC has already developed as an Achieving the Dream™ lead institution. Specifically, we intend to offer paid research internships to actively engage RCC students in our proposed efforts at all of our institutions. Together with President Roberson (Collaborator for this proposal) and members of the RCC faculty, we will advertise between one and five positions each year, ranging from molecular biological-oriented positions at Harvard, WHOI and the University of Minnesota, to geochemical, geophysical, and computational efforts at MIT, WHOI, Lamont Doherty Earth Observatory, NASA-AMES, NASA-JPL, UC Santa Cruz and Scripps Institution of Oceanography. Each advertisement will include a short description of the research effort, the duration of the program (we expect these projects to take ~25 hours/week, and range from one month to four months in time), a distilled guideline of the basic skills that are required, and the appropriate contact information. RCC faculty will work as mediators to foster conversations among the NAI investigators and the RCC students. When needed, RCC faculty will teach the prospective students the required skills over the course of a semester, prior to the student’s participation in a research lab. Once a student and NAI investigator have agreed to move forward, the program will be structured to accommodate the more practical needs of the student. Those RCC students that can reside out of state for several weeks or months would be provided full travel support and a stipend to ensure that this internship does not come at a personal financial cost. Some RCC students may not be able to leave due to personal obligations. In that case, we will have the student pay a short visit to the lead laboratory, but then work with a member of the RCC faculty who will supervise their day-today activities. The NAI investigators will meet with the students frequently, e.g. weekly, via ZOOM.us or other appropriate methods. All interns will be required to produce a data product for their efforts. By design, those data products will be a part of our research activities, so when appropriate the interns will be among the co-authors on the respective publications. In addition to the internships, we will develop and host an RCC “soft skills” workshop at Harvard University (support for this program will come from Harvard discretionary funds). While students from under-represented groups can often excel in the classroom, there can be social and cultural barriers that prevent a student from pursuing particular careers. This two-day “soft skills” workshop will be led by Co-I Girguis, and will include team members Huber and German (and all other Co-Is, as available in person or by Zoom). The first day will consist of an introduction to academic networking, and a Q&A session about job searches and applications. We will also host a resumé and CV workshop, in which RCC students will bring a completed document for review, or will generate their first one in consultation with our team members. We will end day one with dinner at Harvard’s faculty club, which we hope will help reduce any

77 conscious or unconscious barriers about interacting with faculty during interviews at prominent research universities. Day two will consist of mock interviews, both in person and via Zoom. Finally, day two will end with a customized “networking plan” for each student that includes information and resources relevant to their career pursuits, the names of scientists and engineers in their area of interest, and the names of two members of the NAI team who will be their “advocates” while they are completing their studies and in pursuit of jobs. As mentioned, these internships will be paid positions, providing the RCC students with $20 USD per hour (to ensure there are no structural barriers to student engagement, this salary will be constant across all internships, regardless of previous experience). Co-I Girguis will serve as the RCC coordinator, and participating RCC students will be paid through Harvard University. This arrangement provides the most pragmatic approach to employment, allowing Co-I Girguis to leverage other Harvard resources for this program, and reducing the administrative burden on RCC administrators.

Figure 7.2 Roxbury Community College students have routine access to internship opportunities in applied physics and chemistry. Our Exploring Ocean Worlds team will add to their repertoire of options for advanced research in the physical and chemical sciences.

According to RCC leadership, RCC's students are typically looking for exciting, gainful employment in molecular biology and biotechnology, environmental sciences (in particular geochemistry), civil engineering (geophysics) and information technology (Fig.7.2). Many are returning students who perceive that such employment is inaccessible to them. This misconception is propagated by the lack of opportunities to engage in “R1-style” research, which in turn limits the number of students who apply to technical positions at R1 (Doctoral, Highest Research Activity) universities and similar academic institutions, or who pursue more advanced degrees in sciences and engineering. It is our belief that this effort serves to provide a greater number of students to support the proposed research, while simultaneously reducing the

78 barriers that commonly exist among members of underrepresented groups. It is also our hope that this program will continue well beyond the lifetime of this NAI, and that it will serve as a catalyst for a more formal arrangements among RCC and our team’s local R1 institutions. In addition, we expect our co-Is to benefit from more in-depth insights into viewpoints and learning styles through interactions with this group of students and the RCC faculty and to have a chance to develop additional skills in conveying ideas and work methods for diverse teams.

7.4 Professional Community Development An important priority for NAI is the expansion of the astrobiology research community. An immediate contribution that this team would offer to NAI is that our small but experienced and well integrated research team would add astrobiology to the prominent research portfolio of seven well recognized oceanography laboratories across the United States, where the field of astrobiology is not currently prominent. Indeed, for four of our Co-Is, preparation of this proposal has already provided their first direct exposure to NAI and NASA’s Astrobiology program. Within the ocean sciences, however, these same Co-I’s are internationally recognized as leaders in their field. Inevitably, therefore, because our team’s efforts involve the pursuit of astrobiological research within traditionally Earth-centric oceanography research institutions, the reach of NAI will extend out, through our team’s other professional research, education and communications activities, across the international Earth and Ocean Sciences. For example, while travel funding solicited within this proposal includes support for our team members to participate actively in bi- annual AbSciCon meetings, it is inevitable that we will continue to engage actively – including as session organizers and invited speakers – at related international interdisciplinary meetings (not least, bi-annual AGU Ocean Sciences meetings and Goldschmidt Geochemistry conferences) where our work, hence, the field of astrobiology as a whole, will propagate out among our peers. As well as extending the reach and the membership of the astrobiology community, we anticipate that we will contribute new knowledge and capabilities to that community, beyond just the intellectual research to be conducted within this project and the training of a cohort of early career scientists engaged in the investigation of ocean worlds. Specifically, while the program of work proposed here is primarily based on theoretical modelling, validated by complementary laboratory experiments, the majority of the team members that we bring to NAI are also highly seasoned field scientists with many person-decades of experience organizing and leading research expeditions to the deep ocean. For example, through NSF’s national Ridge 2000 program, which was chaired for 3 yrs by Co-I Blackman, all of Co-Is Blackman, Fisher, Huber, Seewald, Thurnherr and Toner, along with PI German, have established past collaborations, in various combinations, conducting interdisciplinary research to investigate interactions between mid-ocean ridge volcanism and tectonism, the physics and chemistry of hydrothermal activity, the functioning of associated chemosynthetic ecosystems, and their impacts on global-scale biogeochemical cycles and ocean budgets. Both Fisher and Blackman have notable experience in deep sea drilling via the International Ocean Discovery Program and its predecessors, the (Integrated) Ocean Drilling Programs. Thus, while all oceanographers, by training, consider the specific processes that they study within the broader context of a single coherent ocean system, our team has an even greater strength in that our shared experience has involved more aggressive pursuit of interdisciplinary ocean research than the majority of our peers. We will stand ready to offer all of that expertise to future NAI ocean worlds programs and researchers. For example, we will be well placed to mentor other members of the NAI community, interested in ocean worlds but new to conducting ocean-based research, in how best to design and implement interdisciplinary ocean research programs, how to gain access to the deep ocean and make best use of key assets including research ships and current state-of-the-art advanced technologies (submersibles, robots, in-situ sensors), and, where required, in designing and testing new systems and sensors to meet future ocean world mission needs.

79 A final important consideration, when discussing contributions to professional development, is that with WHOI as lead institution, PI German would be able to offer partnership to NAI central with one of the most prominent and well-established communications departments in Ocean Science, Engineering and Education, worldwide. The team conducts a full portfolio of activities across traditional and social media and employs specialists in science writing and illustration, web and graphic design, animation and video production as well as a team dedicated to public information. In addition to serving interactions with outside (print and televisual) media the team also maintain dedicated WHOI web-presence, twitter and Facebook profiles and publish the Oceanus magazine which has a 65 year history of communicating research to the public in both printed and, more recently, digital form. From within this team, Ken Kostel (Web Science Writer/Editor) is already internally funded by WHOI to interact directly with PI German in the development of resources related to emerging Ocean Worlds research at WHOI (web.whoi.edu/oceanworlds). For this proposal, they will be joined by Multimedia Technician Matt Barton, who will serve as the dedicated Information Technology specialist for the Exploring Ocean Worlds team. Barton previously took the lead, technologically, in establishing two telepresence research laboratories that German has founded at WHOI (one as an on-campus Institution-wide resource, the other as a dedicated facility in PI German’s laboratory). The latter has ample capacity to also house the videoconferencing unit to be provided by NAI Central for this project (Fig.7.3).

Figure 7.3 PI German’s Telepresence and Videoconferencing facility at WHOI including, at right, telepresence capabilities used most recently for real-time remote direction of robotic exploration for and characterization of new seafloor venting at Pito Seamount in the remote South East Pacific (hydrothermal vents visible on large monitor) in Jan-Feb. 2017.

7.5 Innovative and Effective use of Communications Throughout its history, NAI has pioneered the use of innovative and effective use of communications and information technologies to build and support the astrobiology community. Similarly, over the past five years, PI German has pioneered the use of telepresence in oceanography, seeking to migrate out from the simple one-way communications used

80 previously as an effective outreach method to communicating the excitement of deep sea exploration in real time to a viewing public (for example through the Ocean Exploration Trust’s Nautilus Live and NOAA’s Ocean Explorer portals). Most recently, German has just completed a project funded through the Integrated NSF Support Promoting Interdisciplinary Research and Education (INSPIRE) program. That project sought to establish best practices for the employment of telepresence for deep ocean research and education. The goals were met through an innovative collaboration, funded jointly through NSF’s Divisions of Ocean Sciences, Computer and Information Science and Engineering, and Human Resources and Education and involved interactions with specialists in Ethnography (Kennedy School, Harvard) and Educational Research (the Concord Consortium) as well as Ocean Scientists and Engineers. That work led to the identification of the most intuitive, hence user-friendly web-based information sharing and video communications tools to be used for this project. Indeed, our Exploring Ocean Worlds team members have already been trained to be proficient in using these tools during the preparation of this proposal. Perhaps the best reassurance that this approach has merit for future work within NAI research can be drawn from the success already achieved during our deep ocean investigation. Over the course of the project (www.whoi.edu/treet) we successfully recruited a team of six early career scientists interested in Deep Submergence Science who we mentored over two years so that, together with undergraduate students (rising juniors) that they recruited from their home laboratories, they were able to lead their own series of deep ocean research investigations, remotely, from shore. During year 1 of the project we taught a seminar series online, distributed between nine faculty and six laboratories spanning four time zones, to teach the students about the technologies to be used during the field expedition and the research opportunities available among both the early career team and the mentor team that PI German had assembled. The seminar series culminated, after Spring Break, with the students working in pairs and presenting back to the faculty and their peers on proposals for work that they would also like to undertake during the cruise, in pursuit of their own senior year honors projects. At the outset of Year 2 of the project (coordinated to coincide with the start of the undergraduates’ senior academic year) we assembled our entire team at the Inner Space Center in RI, where, for one week, they worked together in person, populating a rotating 24h watch cycle, to maintain continuous real- time scientific direction of robotic investigations at a suite of seafloor fluid flow sites (arc-volcano vents and subduction-related cold seeps) on the Caribbean seafloor. After a first week of training, the team was then split into two separate groups and the research was continued at the seabed, but with science direction now distributed through two separate institutions, one team each based at the University of Rhode Island and in the first of the Telepresence centers established by PI German at WHOI. The research continued seamlessly for the second week of the expedition, with operations teams at sea aboard the EV Nautilus interacting collaboratively in real-time with scientists simultaneously involved in the research at both shore locations (Fig.7.4). Once the cruise was completed, all participants, equipped with access to a common digital data base, returned to their home laboratories. The following January, one year on from the Y1 seminar series, a second semester-long course was initiated in which, on a week by week basis, the various research teams presented their results to the rest of the community. Outcomes from the cruise were included in a special session on Telepresence-enabled Ocean Research at the most recent AGU Ocean Sciences meeting, two ocean research papers submitted for peer review by the early career teams (Michel et al., In Review; Mittelstaedt and Smart, In Review) and two papers in the educational research literature (Pallant et al., 2016; Stephens et al., 2016). With the completion of the grant in Spring 2017, two final synthesis papers are now being written, one on the ethnography research (Mirmalek & Jasanoff, In Review) and the other capturing best practices and recommendations for future use of telepresence across the national deep ocean research fleet (German et al., In Review).

81 Figure 7.4 PI German’s remotely conducted field program that investigated methods in using telepresence for exploration, Fall 2014. Anti-clockwise from top right: a) early career geophysicist Eric Mittlestaedt (far right) with geology and biology undergraduates from U.Idaho and Harvard as they prepare to take command of scientific operations from their telepresence station, WHOI; b) location map showing trajectory of the research ship EV Nautilus between the Kick’Em Jenny seamount (KEJ) and the Barbados Mud Volcanos (BMV); c) live video-feed of mussel community associated with active methane-rich fluid flow at BMV site; d) & e) contemporaneous photographs of U.Idaho student Taylor Westlund directing real-time ROV operations at the BMV cold seeps, from WHOI, while in direct contact with PI German who provided real-time mentoring from URI.

We look forward to an opportunity to share the knowledge gained from this project with NAI and the wider Astrobiology and NASA space exploration communities. Superficially, our investigations, conducted in a deep ocean exploration context, may appear to be relevant only to astrobiology researchers interested in Ocean World research. What we believe will be found to be of much wider significance, however, will be the experiences gained, and the lessons learned, as we have developed methods that allow multiple PI led teams to work together, across multiple locations and with diverse and often conflicting research priorities, to make maximum time-critical but effective use of a single high-value asset that was, in turn, remote from the operational centers for any of the PIs involved in the exploration. Indeed, just as this proposal was being finalized one such application was funded by NASA’s PSTAR program – using our experience in latency in communications during deep ocean exploration to prepare for future astronaut-led missions to Mars (see Current & Pending for PI German: Project SUBSEA).

82 8. Relevance

Ocean worlds have become a prominent focus of NASA’s Planetary Sciences endeavor. During the last three years, NASA has selected instruments for the Europa Clipper mission, conducted a detailed study of a possible Europa Lander mission, identified Enceladus and Titan as targets of interest for the current New Frontiers mission opportunity, and established the Roadmap to Ocean Worlds strategic planning activity. The widespread interest in ocean worlds is focused around their potential to host extant life, and astrobiology objectives feature prominently in each of these activities. It is therefore essential that the astrobiology, planetary sciences, and ocean sciences communities partner to provide the scientific context for the exploration of worlds. This must happen now, and continue to inform strategy as the program of ocean world exploration evolves. Our work is proposed in exactly this spirit: our guiding question, our research objectives, and the interdisciplinary team assembled to pursue them are purpose-built to support the astrobiological exploration of ocean worlds.

The relevance of our project to NASA is ultimately traceable to NASA’s Strategic Plan (NASA, 2014a, Strategic Objective 1.5: Ascertain the content, origin and evolution of the Solar System and the potential for life elsewhere) and the Planetary Sciences Decadal Survey for 2013- 2022, Visions and Voyages, Cross-cutting Theme 2: Planetary habitats – searching for the requirements for life… …and do organisms life there now? (NASA, 2011). The work detailed in this proposal will advance our current state of knowledge for assessing whether or not the requirements for life are satisfied within ocean worlds, and our work will inform and enable future efforts to determine if life exists there now now (see section 8.1). In addition, our relevance maps directly to the 2015 Astrobiology Strategy Document’s Major Topic 5: Identifying, exploring and characterizing environments for habitability & biosignatures (NASA, 2015). Our work will directly address Topic 5 (see, specifically, Sections 5.4.I, 5.4.II, 5.4.III; NASA, 2015) by: (i) Providing analysis that enhances the scientific return of current and forthcoming space missions directed at astrobiology targets; (ii) Informing instrument development activities by identifying measurement capabilities that would best support a search for life; (iii) Conducting fundamental research in planetary and ocean system science that will also be of clear and critical longer-term relevance; and (iv) Helping to establish long-term, synergistic collaborations with other agencies that will help advance the development of methods and technologies relevant to ocean world exploration.

8.1 Mission Relevance

We propose work designed specifically to inform and support ocean world astrobiology missions, as articulated in both our guiding question and our specific objectives. Our proposal responds to what we see as an emerging need in ocean world science. At a programmatic level, the emphasis is evolving from characterizing the habitability of ocean worlds to seeking evidence of life thereon. This is vividly demonstrated by the differing goals, formulated just 5 years apart, of the Europa Clipper mission and the Europa Lander mission concept (Clipper: “explore Europa to investigate its habitability”; Lander: “search for evidence of life on Europa”), and by the stated goals of the New Frontiers 4 Announcement of Opportunity (“The Ocean Worlds mission theme is focused on the search for signs of extant life and/or characterizing the potential habitability of Titan and/or Enceladus”). The relevant scientific communities – astrobiology, planetary sciences, ocean system sciences – must respond to this new emphasis with new science that enables the search for life on ocean worlds to be conducted on the best possible footing. Specifically:

83 The presence of life in a given environment does not guarantee that it can be detected. As vividly illustrated by Earth’s diverse ecosystems, the abundance of life and the evidence it presents of itself can vary dramatically. Were all the ocean worlds of the outer solar system inhabited, we could still expect that the nature and abundance of evidence for life might vary dramatically among them. To optimize the potential for detecting life, if it is present, we should ask: On which ocean worlds, and with what measurements, will we have the greatest potential to successfully detect the presence of life? This is, in fact, the single question that motivates and guides the work we propose. We expect that detectability is governed by a complex network of processes and factors, but also that this network can be understood and modelled in order to identify observational constraints thereon.

The emphasis on identifying observations that can meaningfully constrain biological and biosignature potential is motivated in a significant way by the experiences several of our team have had as ocean world astrobiology Science Definition Team members (Europa Clipper: Hand, Hoehler, Shock; Europa lander: Hand (co-chair), German, Hoehler), Project Science Group members (Europa Clipper: Hand, Shock), New Frontiers proposers (Hand, Hoehler, Huber, Sotin), and Roadmap to Ocean Worlds contributors (German (“Oceans” co-lead), Hoehler (“Habitability” co-lead), Hand, Shock, Sotin). At differing levels, each of these activities requires the team to assess how specific measurement capabilities – not just measurement type, but also detection thresholds and precision – address larger astrobiology objectives and goals. Moreover, the reality of payload mass and resource limitations typically requires that measurements be prioritized on the basis of how much information each delivers in relation to specific objectives and overall goals. The scientific underpinning needed to do this analysis in a rigorous way – to provide thorough, quantitative rationale for specific measurement priorities and requirements – is often not as well developed as it needs to be. Our work seeks to address this need. Our intent is to develop an interpretive framework that is not specific to a given place or mission, but is instead transposable across the breadth of ocean worlds and the missions that have visited or will visit them. By this virtue, the proposed work connects to several existing and forthcoming missions:

a) Enhancing the scientific yield of existing and forthcoming mission data

Cassini has, for the last decade, provided a rich source of data for Enceladus, using instruments that were never designed to assess habitability there. (Indeed, the ocean and plumes of Enceladus were not known until their discovery by the Cassini team.) In particular, the Ion and Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA) have provided compositional data that can serve to constrain ocean chemistry and, potentially, also the processes that influence it. These include observations of sodium chloride (Postberg et al., 2009), a number of volatiles (including, recently, H2; Waite et al., 2017), CO2/carbonate ratios that have been used to constrain ocean pH (Glein et al., 2015), and silica nanoparticles used to suggest the occurrence of hydrothermal venting (Hsu et al., 2015). Several efforts have used these data as they emerged to constrain chemistry and processes that might impact biological potential (Glein et al., 2015; Waite et al., 2017). Our work can augment these efforts by placing Cassini data in a context specifically designed to assess biological and biosignature potential. In fact, the reanalysis of Enceladus compositional data in the context of biosynthetic potential is included as an explicit component of Task 3-6. This effort would bring two key advances to the analysis of Cassini data as it bears on Enceladus astrobiology. First, via the massive forward geochemical modelling of Investigation 3, we can eliminate the need for going-in assumptions about composition and reaction conditions on Enceladus, and thus avoid the potential for bias that comes with modelling based on assumed compositional inputs. Moreover, geophysical and geochemical constraints are explicitly coupled in our efforts, and may introduce feedback or

84 control mechanisms that have yet to be fully accounted for. The intent to integrate observational constraints from both geophysics and geochemistry is a hallmark of our effort, not just for Cassini/Enceladus, but also in the broader context of ocean world missions.

In contrast to Cassini at Enceladus, Europa Clipper will bring to bear a payload designed to characterize habitability. Indeed, given that Hand, Hoehler, and Shock served as members of the Clipper Science Definition Team, the conceptual approach reflected in this proposal was also inherent in the formulation of the Clipper science investigations. In particular, Clipper could yield a rich set of compositional constraints on the Europan ocean via observations from MISE (mapping infrared spectrometer), MASPEX, (time of flight mass spectrometer), SUDA (mass spectrometric particle composition analyser that can localize particle source region), and ICEMAG/PIMS (magnetometer and plasma analysis suite). In our analysis, these constraints can serve as indicators of geochemical processes that govern resource fluxes. For example, bulk constraints on salinity (ICEMAG/PIMS) can constrain overall (integrated) water:rock reaction ratios while analysis of salt composition (MISE/MASAPEX/SUDA) can constrain compositional inputs and reaction conditions. These will be complemented by observational constraints on heat flux (E-THEMIS) and ocean thickness and volume (ICEMAG/PIMS and gravity science), which can be integrated via the hydrogeology, ocean circulation, and residence time modelling components of our approach. Moreover, PIMS will yield direct observational constraints on the quality and intensity of surface radiation at Europa, which can be used in conjunction with the irradiation experiments in Investigation 6 to characterize the impact of radiation processing on (bio)geochemical tracers delivered to an ocean world surface. Finally, SUDA is a successor instrument to Cassini’s CDA (cosmic dust analyser), which provided the silica nanoparticle observations used to infer that hydrothermal venting occurs on Enceladus. The particle characterization work of Investigation 6 provides expanded context for comparable observations that might be made at Europa. Thus, our work will provide an interpretive context in which to integrate several of the Clipper science investigations in assessing biological potential. In particular, the suite of instruments plays to the hallmark of our approach – to combine geochemical and geophysical observations as constraints on biological potential. The integrative framework will be in place by the time Clipper commences its observing campaign. Importantly, Hand (SUDA) and Shock (MASPEX) now serve as part of the Project Science Group. This involvement ensures that the findings and tools that emerge from our work can be fully considered and utilized by the Clipper PSG, both in pre-launch planning and once the observing campaign at Europa begins.

b) Preparing for future missions

The Europa Lander mission concept, which has now completed a pre-Phase A Science Definition process and Mission Concept Review, would advance the emphasis at Europa from assessing habitability to searching for life, but does still retain a habitability-themed objective as its second priority. Hand (co-chair), German, and Hoehler served as part of the Lander Science Definition Team, and deliberations as part of that activity provide much of the motivation for this proposal, and the objectives we will pursue. Should Lander move forward, with a prospective launch date in the mid-2020’s, the instrument development and payload integration process would unfold largely in parallel with our proposed work, such that our findings could influence that process as it occurs. In particular, we seek to inform measurement requirements and desirable measurement capabilities in two ways. First, for investigations that seek evidence of life in any of several forms (e.g., Lander Objectives 1A, B, and C), our work will help to constrain estimates of in situ cell abundance, enantiomeric excess, and concentrations of overall or specific organics, and thereby identify desirable measurement capabilities (e.g., detection thresholds) as instruments are being developed. During the science definition process,

85 measurement requirements were set to correspond to low productivity and physically analogous environments on Earth, specifically because the interpretive framework and existing data do not currently support precise estimates for Europa. Our work is intended to fill this need. In fact, it is exactly this experience during the science definition process that motivated our proposal. Second, the Lander SDT emphasized the importance of measurements that establish environmental context (Objective 1D) and constrain habitability (biological potential; Objectives 2A and B). In particular, one intent of these investigations is to constrain detectability, so that an ambiguous or negative result for life detection could be placed in context: Could life be there but, by virtue of low productivity, insufficient transport, or efficient destruction, fail to express itself at a level that our instruments can detect? Our work is purpose-built to this task: it will provide a means of integrating the diverse physical and chemical data products of Clipper and Lander to place quantitative constraints on Europa’s potential to express evidence of itself at the point of sampling.

8.2 Fundamental Research to meet NASA’s long-term strategic needs.

In this proposal, our intent is that our work will provide an interpretive framework that is transposable across all ocean worlds and missions, so that it can be used to inform the strategy for ocean world exploration going forward. Specifically, as articulated in our guiding question, our work is designed to provide a scientific basis for prioritizing both specific targets for ocean world exploration and the development of new measurement capabilities that will best enable that exploration. Consistent with this, our work will be relevant to three goals in the Roadmap to Ocean Worlds Goals, Objectives and Investigations report (NASA 2017b): Goal II: Characterize the ocean on each ocean world (PI German is co-lead for this goal) Goal III: Characterize the habitability of each ocean world (Co-I Hoehler is co-lead). Goal IV: Understand how life might exist at each ocean world...

Historically, considerations of habitability had been predicated on a simple “binary” approach (e.g. Cockell et al., 2016). More recently, however, approaches to our understanding of habitability have become increasingly nuanced (NASA, 2015). It is now widely accepted that the key ingredients for habitability that likely need to be met include not just water but also: key bio- essential elements (starting with the CHNOPS elements), a source of exploitable energy available to sustain life, a suitable combination of physical and chemical environmental conditions to render a system habitable; and sufficient time for life to become established and, hence, detectable. Just as Earth provides a spectrum of inhabitable niches, so too do the biological abundance and biodiversity that can be observed vary widely across our home planet in response to a wide-ranging diversity of environmental parameters. We should anticipate that the same diversity of habitability and life should also arise on other habitable and/or inhabited ocean worlds. Herein lies the strength of our team’s approach: It is not specific to any given world, nor to any specific set of observations. Rather, we will establish a framework that can accommodate a diverse set of observational constraints, such as might be delivered by differing payloads, in pursuit of the same basic objective – to assess biological and biosignature potential.

By adopting an ocean systems approach to ocean world exploration, blending geophysical as well as geochemical approaches to arrive at assessments of biological potential and biosignature potential we will achieve two major objectives. First, we will provide the astrobiology and planetary sciences communities with a new tool for use in the exploration of ocean worlds – an interpretive framework that links geophysical and (bio)geochemical observations to biological and biosignature potential. Second, our project will help NASA to identify what new measurements will offer the most diagnostic indicators for biological and biosignature potential when added to an existing suite of measurements

86 available for future spacecraft missions. This would certainly be important in the case of a New Frontiers mission to Enceladus, where Cassini has already delivered a diverse set of compositional constraints. Importantly, our analysis will unfold within a timeframe that could inform priorities for measurement capability as instruments are being optimized for flight. Perhaps as important as the results and tools that we will bring to this endeavour however, when considering NASA’s long term research needs, is that this project will establish a team that adds new and valuable expertise in ocean system science to the study of ocean worlds: by partnering that expertise with established researchers in astrobiology and planetary science we will be able to work integratively to understand how the complex network of processes that govern biological and biosignature expresses itself among the Solar System’s ocean worlds.

8.3 Synergistic Collaborations

This project is focussed on developing a theoretical basis for predicting the potential to detect evidence for life on Ocean Worlds beyond Earth. But the team members selected for this work were selected precisely because they also share a wealth of experience in the planning and implementation of complex and integrated inter-disciplinary field programs of deep ocean exploration and characterization. (Note, for example, that the images used on the cover of this proposal were all collected by members of our research team, in the field. Top: during first under ice ROV dives searching for hydrothermal venting on the Gakkel Ridge; middle: investigating chemosynthetic microbial activity associated with novel asphalt flows in the Gulf of Mexico (courtesy of Ian MacDonald); bottom: investigating ~100°C, hydrogen-rich serpentinization- related hydrothermal venting on the Mid Cayman Rise). This is important because, both in parallel with this project and beyond the lifetime of the CAN8 cycle, adding our team to the NAI community will open up a network of new pathways for collaborations between NASA’s astrobiology community interested in Ocean World research and other Federal Agencies, notably the National Science Foundation’s Division of Ocean Sciences, NOAA’s office of Ocean Exploration and Research and the US Navy’s Office of Naval Research. Our team members have strong track records of funded research through all of those agencies to study different processes relevant to the work proposed here and also, importantly, to the development of advanced robotic vehicles and in situ sensor payloads to conduct that research. As the exploration of the Solar System’s ocean worlds progresses, we anticipate that partnerships to be developed through this research program will prove invaluable. A major anticipated outcome from this program will be to identify priorities for new technology requirements for future ocean world missions that can be prototyped and time-efficiently field tested at suitable Earth analog settings as important first steps along the path of Technical Readiness Level evolution that needs to be completed prior to spaceflight. Examples of how such partnering can succeed are already becoming apparent through programs with which members of our team are already involved. Expertise that has been pioneered within the ocean sciences community but which is now being investigated for possible adaptation to astrobiology needs includes development of in situ instrumentation for the study of seafloor life (Co-I Girguis; PSTAR) and operational research, investigating the appropriate blend of autonomy and humans-in-the-loop for both robotic and human-led missions of exploration (PI German; PSTAR, NOAA Ocean Exploration Program, Office of Naval Research). Continuing collaboration between astrobiologists, planetary scientists and ocean scientists will provide a natural synergy in which to develop and provide for further technological development to meet astrobiology needs. The importance of the work proposed here is that it will establish the scientific basis upon which to identify and prioritise those needs as we continue the search for life beyond Earth and, specifically, the exploration of ocean worlds.

87 9. Facilities and Resources

This project will draw upon expertise among theoretical and experimental scientists drawn from across the planetary, astrobiology and ocean sciences. The key facilities and resources, beyond conventional office-level computing equipment, that will be brought to bear in this project, therefore, are a combination of sophisticated modeling approaches with which our team has well established experience (many of the models have been developed by our Co-Is) together with a suite of purpose developed research laboratories in which our (bio)geochemical and microbiological experiments will be undertaken.

9.1 Theoretical Models

Physical Models: Co-I’s Sotin and Blackman (Investigation 1) will utilize a suite of proprietary geophysical models developed over the course of their careers for investigating tidal dissipation in the rocky interiors of outer solar system satellites and seafloor flexure, respectively. Of particular note for our hydrogeology work (Investigation 2), Co-I Fisher will use the Finite Element Heat and Mass (FEHM) model developed at Los Alamos National Laboratory (Zyvoloski et al., 2011). FEHM is a node-centered rock-fluid-solute flow simulator and uses a finite-volume approach to represent properties and solve for coupled and transient fluid flow and heat transport. FEHM solutions are calculated using a fully implicit solver with upstream weighting. FEHM also has capabilities in solute and reactive transport, dual-porosity/dual permeability domains, and multiphase flow. Simulated regions are represented using unstructured grids with tetrahedral or hexagonal geometry that are constructed with LaGrit. UCSC and LANL collaborators have built numerous pre- and post-processors for use with FEHM, run simulations on multiprocessor workstations, and visualize model output using custom scripts developed with Matlab, Python and Paraview. For Ocean Circulation (Investigation 5) Co-I Marshall will use MITgcm - a state of the art General Circulation Model of the ocean developed by John Marshall and his group (Marshall et al., 1997a,b; Adcroft et al., 2004), which includes the capability to represent a global ice shell and the associated ocean-ice processes. The MITgcm has been used with success in a range of aquaplanet, planetary and exoplanet applications (e. g. Goodman et al., 2004; Marshall et al., 2007; Ferreira et al., 2011, 2014; Kaspi et al., 2009; Parmentier et al., 2016) as well as numerous (more than 1000) studies of the Earth's ocean.

Geochemical Models: Co-I’s Shock and Hoehler (Investigation 3) will predict the consequences of fluid-rock reactions using an automated and integrated system of computer codes (EQ3, EQ6, DBCreate, SUPCRT, CHNOSZ). All calculations will be conducted from 0 to 400°C at pressures up to 500 MPa, and will utilize the thermodynamic data for aqueous species generated by Co-I Shock and members of his research group (Shock et al., 1989, 1997; Sverjensky et al., 1997; Plyasunov and Shock, 2001; Dick et al., 2006; LaRowe & Dick, 2012; Canovas & Shock, 2016). The reaction path calculations and operations on the resulting database will be conducted using the Pleiades supercomputer at NASA Ames. In preparation for this proposal, Research Associate Sanjoy Som, who has previous experience in coding for the parallel architecture of Pleiades, assessed its performance on a suite of benchmark calculations that correspond closely to those proposed for Tasks 3-5 and 3-6. On this basis, we estimate that Pleiades at full capacity would complete 10 million reaction path simulations in approximately 10 minutes, whereas a typical desktop would require > 1 year. More realistically, given the typical subscription rate of Pleiades, we estimate that the task could be completed in approximately 3 hours.

88 9.2 Experimental Laboratories

Geochemical Laboratory (WHOI): Co-I Seewald (Investigation 4) has a modern laboratory at WHOI equipped with hoods, balances and deionized water. The laboratory houses a state-of- the-art experimental hydrothermal facility equipped with 4 sets of flexible-cell hydrothermal apparatus and an all titanium flow-through apparatus. There are 8 isobaric gas-tight fluid samplers in the lab that will be used for conducting microbial incubations at in situ pressure. All necessary furnaces, temperature controllers, and pressure measurement and control devices necessary to conduct this study are present in the laboratory. Analytical equipment includes two Dionex DX-500 ion chromatographs equipped with anion and cation columns, conductivity and electrochemical detectors, and autosamplers, a Hewlett Packard 6890-5973 gas chromatograph - mass spectrometer equipped with on-column and split-splitless injectors, flame ionization detector, and autosampler, a Hewlett Packard 5890 II gas chromatograph equipped with serially connected thermal conductivity and flame ionization detectors, and a Hewlett Packard 5890 gas chromatograph equipped with thermal conductivity and helium ionization detectors. Both the Hewlett Packard 6890 GCMS and 5890 II GC have cryogenic cooling capabilities and are directly interface to a purge and trap device. A flow injection analysis that involves membrane diffusion separation and conductivity detection is available for analysis of ΣNH3. A Finnigan MAT DELTAplusXL that can be configured for GC-IRMS carbon and hydrogen isotope analysis is also located in Seewald’s laboratory. The WHOI ICP-MS facility include a Finnigan MAT ELEMENT II high resolution ICP-MS that is available for analysis of dissolved metals and major cations. Also available for this study are a Horiba LabRam HR800 confocal Raman spectroscopy system and a Hitachi TM3000 scanning electron microscope with an energy dispersive spectrometer (SEM-EDS).

Geobiology Laboratories (Harvard): For this project, Co-I Girguis (Investigations 4 and 6) will make primary use of his ~2,500 sq. ft. physiology lab which includes a full high- pressure/temperature bioreactor facility (HPRF). The HPRF (Fig.9.1) is unique in that it allows for up to twelve flow-through high-pressure vessels to be run indefinitely and independently (yet concurrently when needed) at quasi-in situ conditions. Eight counter-current exchange gas equilibration columns, equipped with gas mass flow controllers and proportional pH controllers allow for up to eight different geochemical compositions, which can be used independently or mixed to provide thousands of different geochemical compositions. Six high-pressure industrial diaphragm pumps as well as numerous high-pressure liquid chromatography pumps are used to maintain flow. The HPRF hosts six 500 mL titanium vessels, four 1. 5L titanium vessels, and four 3L acrylic lined vessels (useful for trace metal experiments). The Figure 9.1 The HPRF facility at Harvard can be configured to HPRF also hosts numerous host up to 12 flow-through high-pressure systems. small pressure vessels that can be used in batch. All are

89 capable of operating at pressures >300 atmospheres (~4,300 PSI). In addition, five Parr™ high- pressure reactors also reside in this laboratory, and are capable of incubating samples at in situ pressures and –as needed- at elevated temperatures for studying extremophiles. The lab also houses our mobile mass spectrometer for respirometric studies. The physiology lab also hosts two chemostats (a BioFlo 1L and a Sartorius 10L) as well as numerous smaller-scale flow- through reactors. All reactors can also be fed by our 8,000 liter flow-through seawater system that is filter and UV-sterilized, as well as aerated and pH and salinity controlled via proportional control systems. The lab is also equipped with two anaerobic hoods, anAgilent™ UV-visible diode array spectrophotometer, temperature controlled circulating waterbaths, two in situ mass spectrometers, an in situ stable carbon isotope analyzer, two Agilent™ gas chromatographs equipped with a TCD and FID detector respectively, and a new Agilent™ 5977A GC/MSD system for metabolomics analyses.

Microbiology Laboratory (WHOI): Co-I Huber (Investigations 4 and 6) has recently moved into a new 950 sq. ft. laboratory space in the Watson building on WHOI’s Quissett campus that is designed for microbial biogeochemistry. Instruments include pH meters, balances, Beckman centrifuge, Eppendorf microcentrifuge, filtration systems, shakers, chemical flow hoods, refrigerators, -20°C and -80°C freezers, Stratagene 2400 UV crosslinker, and SpeedVac concentrators. Microbial analysis will be supported by anoxic bioreactors for batch-fed and chemostatic cultivation with gas, temperature, and pH controls; a gassing manifold for vacuum evacuation and gas flushing of liquids and vials; a Coy anaerobic chamber for anoxic media and sample preparation; and forced-air growth incubators. Additional items include steam autoclave, Air Clean PCR workstations, real-time PCR thermal cycler, Eppendorf electroporator, rotary hybridization oven, Eppendorf MasterCyclers, Invitrogen Qubit Fluorometer, LabChip GX, Bio- Rad gel documentation systems, Zeiss Axioskop 2 microscope, preparative ultrancentrifuge with rotors, deionized water systems, and DNA/RNA electrophoresis equipment for nucleotide quantification and separation.

Biogeochemistry Laboratory (UMN): Co-I Toner (Investigation 6) has an aquatic geochemistry laboratory at UMN that is equipped with the basic equipment needed for synthesis and handling of samples in controlled particle and redox conditions (glove bags and laminar flow benches). Other relevant resources for this project include, a 6-foot Thermo Scientific 1300 Series A2 Biological Safety Cabinet with HEPA-filtered airflow pattern (laminar flow hood), a Coy Vinyl Anaerobic Chamber Type B with positive-flow interlock, a ceiling mounted HEPA work area (where MilliQ water system is located), and transportable bench-top HEPA work station. The Toner lab has re-useable field sampling and shipping materials from previous cruises for oxygen-sensitive samples: e. g. portable glove bags, mylar heat sealers, gas regulators, extension cords, hard-sided coolers and gel packs. Most important for this project, however, will be Toner’s use of Synchrotron-Radiation Facilities. These are national user facilities operated by the U. S. Department of Energy. X-ray diffraction and absorption spectroscopy approaches will be used to characterize the chemistry, structure, and morphology of particles. Micro-probe X-ray fluorescence (µXRF), X-ray diffraction (µXRD), and X-ray absorption spectroscopy (µXAS), and scanning transmission X-ray (spectro)microscopy (STXM) will be conducted at the Advanced Light Source (ALS), Berkeley, CA. Access to this synchrotron facility is earned through a competitive external peer review process, and will be Co-I Toner’s responsibility. Toner has a proven track record of more than 15 years of continuous and successful access to these facilities for her research.

90 Icy Worlds Simulation Laboratory (NASA-JPL): Co-I Hand (Investigation 6) runs this laboratory jointly with R. W. Carlson. The laboratory (Fig.9.2) hosts two ultra-high vacuum chambers (named Minos and Rhadymanthus after features on Europa) that serve as ‘Ocean world in a can’ experiment facilities. Each chamber is equipped with a cryostat, an electron gun (Minos with Emax of 100 keV and Rhad with Emax of 100 keV) and a Fourier Transform infrared spectrometer (FTIR). The systems are constructed of machined stainless steel component (Kimball Physics) and use Conflat® flanges with Cu gaskets throughout. The central chambers have ports for the horizontally-oriented cryostats. Minos has a Faraday cup on a rotation stage for monitoring electron beam current, and a MKS quadrupole mass spectrometer (1-300 amu) capable of residual gas analysis (RGA). The chambers have Varian 300 l/s turbopumps, with purging to protect the bearings from corrosive gases. The turbopumps are backed oil-free Alcatel forepumps, also with purging for corrosive and condensable chemicals (NH3, H2S, H2O, etc.). Films are grown by vacuum deposition of mixed gases. The chambers are not baked but have a base pressure of ~ 1×10-8 Torr with the cryostat off. When operating, the pressure is ~5×10-9 Torr. The Rhad chamber has a high-performance mass spectrometer (Hiden IDP) capable of RGA plus secondary ion mass spectroscopy (SIMS) and sputtered neutral mass spectroscopy (SNMS). This chamber also has a 5 keV ion gun and a translation stage with bellows that allow for up to 12 samples to be irradiated during a single run. Both chambers were custom built by Carlson and Hand with previous funding and they both represent highly-unique capabilities, especially the Rhad chamber with SIMS, irradiation with ions + electrons, and a sample translation stage.

Fig.9.2 The “Icy Moons Simulator Laboratory at NASA JPL

91 Christopher R German (P-I) Geology & Geophysics Woods Hole Oceanographic Institution 266 Woods Hole Road, MS #24 Woods Hole, MA 02543 508-289-2853

Experience Related to the Investigation: PI German is an internationally recognized scientist with >25 years’ experience pursuing interdisciplinary research programs across the Earth-Ocean-Life Sciences and leading national and international programs (see: Fit to NAI section, below). His specialization is in marine geochemistry with a particular expertise in the exploration for and investigation of novel seafloor fluid flow systems: their geologic controls, their impacts on planetary-scale biogeochemical cycles, the chemosynthetic ecosystems that they can support, and the advanced technologies required to locate and characterize them. His work has led to the discovery of new hydrothermal fields in every major ocean basin on Earth and his research has converged, increasingly, with that of astrobiology over the past decade. Most recently, he has served as a member of both the Europa Lander Science Definition Team (NASA, 2017a) and NASA (OPAG)’s Roadmap to Ocean Worlds group, where he is Co-Lead for Goal II: Characterize the ocean on each ocean world (NASA, 2017b).

Education: B.A. – Natural Sciences (Geology & Chemistry), University of Cambridge, UK –1984 Ph.D. – Marine Geochemistry, University of Cambridge, UK –1988

Appointments: Senior Scientist, Geology & Geophysics, WHOI - 2005-present Chief Scientist, National Deep Submergence Facility, WHOI - 2006-2014 Senior Principal Scientific Officer, Southampton Oceanography Center, UK – 2002-2005 Principal Scientific Officer, Southampton Oceanography Center, UK – 1995-2002 Principal Scientific Officer, Institute of Ocean Sciences, UK – 1994-1995 Senior Scientific Officer, Institute of Ocean Sciences, UK – 1992-1994 Higher Scientific Officer, Institute of Ocean Sciences, UK – 1990-1992 NATO Post-Doctoral Research Fellow, Earth, Atmos & Planet Sci., MIT – 1988-1990

Honors/Awards: Smith Chair for Excellence in Oceanography, WHOI – 2016 Fellow, The Explorers Club - 2015 Research Prize, Alexander von Humboldt Foundation, Germany – 2014 Excellence in Partnering Award, National Ocean Partnership Program – 2011 Research Prize, Peterson Foundation, Germany - 2010 Outstanding Research Paper Award, NOAA –2006 MBE Medal, HM Queen Elizabeth II, UK – 2002 Edward A Flinn III Award, International Lithosphere Panel – 2000 Scientist for the New Century Award, Royal Institution, UK – 2000 Fellow, Challenger Society for Marine Science, UK - 2000 Outstanding Research Paper Award, NOAA – 1996 John Murray Student Prize, Royal Society, UK – 1988

92 Select Recent Publications (*Student or Post-doc mentored by CRG) *J.M.McDermott, S.P.Sylva, S.Ono, C.R.German & J.S.Seewald. Geochemistry of fluids from Earth’s deepest ridge-crest hot-springs: Piccard hydrothermal field, Mid-Cayman Rise. Geochim. Cosmochim. Acta, in review. *J.N.Fitzsimmons, S.G.John, C.M.Marsay, C.L.Hoffman, S.L.Nicholas, B.M.Toner, C.R.German & R.M.Sherrell. Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange. Nature Geoscience 10, 195-201, doi:10.1038/NGEO2900, 2017. C.R.German, K.A.Casciotti, J.C.Dutay, L.E.Heimbürger, W.J.Jenkins, C.I.Measures, R.A.Mills, H.Obata, R.Schlitzer, A.Tagliabue, D.R.Turner and H.Whitby. Hydrothermal impacts on trace element and isotope ocean biogeochemistry. Phil. Trans. Roy. Soc. A 374, doi: 10.1098/rsta.2016.0035, 2016. B.M.Toner, C.R.German, G.J.Dick & J.A.Breier. Deciphering the complex chemistry of deep-ocean particles in the ocean using complementary synchrotron X-ray microscope and microprobe instruments. Accounts of Chemical Research 49, 128-137, 2016. C.R.German, S.Petersen & M.Hannington. Hydrothermal exploration of Mid-Ocean Ridges: where might the largest sulfide deposits be forming? Chem. Geol. 420, 114-126, 2016. *M.L.Estapa, J.A.Breier & C.R.German. Particle dynamics in the rising plume at Piccard Hydrothermal Field, Mid-Cayman Rise. Geochem. Geophys. Geosystems 16, 2762-2774, 2015. J.A.Resing, P.N.Sedwick, C.R.German, W.J.Jenkins, J.W.Moffett, B.M.Sohst & A.Tagliabue. Basin- scale transport of hydrothermal dissolved metals across the South Pacific Ocean. Nature 523, 200-203, 2015. *J.McDermott, J.Seewald, C.R.German & S.Sylva. Pathways for abiotic organic synthesis at submarine hydrothermal fields. PNAS 112, 7668-7672, 2015. C.R.German, L.L.Legendre, S.G.Sander, N.Niquil, N.Lebris, G.W.Luther III, L.Bharati, X.Han & N.Le Bris. Hydrothermal Fe cycling and deep ocean organic carbon scavenging: model-based evidence for significant POC supply to seafloor sediments. Earth Planet Sci Lett. 419, 143-153, 2015 C.R.German and W.E.Seyfried Jr. Hydrothermal Processes. In: Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, Vol. 8, pp. 191-233, Oxford: Elsevier.

Fit to NAI: Research Leadership: PI German is an internationally recognized scientist who is held in high regard for his ability to lead complex interdisciplinary teams of highly talented scientists - whether in pursuit of his own deep-ocean research or, more broadly, in support of International Programs. In the past decade he has served as Co- Chair for international programs in each of the Earth, Ocean and Life Sciences with, respectively: • InterRidge / Interdisciplinary Studies of Mid-Ocean Ridges (Co-Chair, 2007-2009) • SCOR WG 135 / Impacts of venting on the global C cycle (Co-Chair, 2009-2014) • Census of Marine Life / Chemosynthetic Ecosystems (Co-Chair, 2003-2010) German’s ability to bring vision to such positions has not only been recognized through his research. In the UK, he was called upon to chair the Research Development Committee, tasked with developing the first coherent research strategy spanning the Nation's Southampton Oceanography Centre (2002-05). In the US, as Chief Scientist for the National Deep Submergence Facility at Woods Hole (2006-2014), his responsibilities included working with US scientists and WHOI engineers on the complete overhaul and rebuild of the Alvin submersible - a project with an anticipated legacy of the order of 50y. Most recently he has served on the Europa Lander Science Definition Team (NASA, 2017a), Co-Led the Goal II team for the Roadmap for Ocean Worlds (NASA, 2017b) and organized and served as lead co-chair for the most recent Ocean Worlds meeting hosted at the National Academy of Sciences in August 2016.

93 Vision: German first presented his long-term vision to use autonomous underwater vehicles to seek out life- sustaining sites of seafloor fluid flow beneath ice covered oceans during his Scientist for the New Century award lecture at the Royal Institution, London in 2001. That led to invitations to share his ideas at NASA-JPL in 2002, and again in 2005, after he had completed the first successful demonstration of the approach: finding the first submarine vents in the South Atlantic. In 2003, German was a founding member of the Astrobiology Society of Britain and served on its inaugural steering committee until he left the UK in 2005. From 2009-2014, German led a NASA-ASTEP research team using a prototype hybrid ROV to locate new sites hosting abiotic organic synthesis in the deep ocean – a project that also provided new insights into how planetary-scale tectonics can shape patterns in marine biogeography. In a successor PSTAR program for which German is the PI, he successfully led the first combined autonomous and remotely tethered dives to the seafloor of an ice covered ocean (Arctic Ocean, Sept-Oct 2016), using a successor to the ASTEP prototype vehicle, and helped discover the first high temperature vents in that ocean.

Interpersonal Skills & Communication: German’s communication skills have been honed from many years of research at sea where the diverse community working together in close quarters, often in arduous conditions, relies upon everybody aboard ship working together to a common purpose - to keep the ship functioning as both home and research platform for all, to keep morale high, and to ensure that all equipment remains fully operational for the program to proceed - whether as used in ship-board science laboratories or as deployed to the bottom of a hostile ocean. His ability to harness the desires and potential of multiple interests and points of view and channel them into a coherent forward path were developed further during his term as Chief Scientist for Deep Submergence at WHOI where his responsibilities included representing the science needs of the entire US research community and conveying those into recommendations and implementation plans for the engineers at WHOI who operate the National Deep Submergence Facility (NDSF). Two particularly notable outcomes were: • the most significant upgrade of the Alvin human-occupied vehicle over its 50y history • the introduction of autonomous robotic vehicles into the national facility

Innovation & Technology: German is an aggressive user of innovative technology. His most recent research in this area concerns the relative merits of human- vs robotics-led exploration – a topic that that informs astrobiology and space research as much as it does the deep ocean. German’s most recent interests, therefore, have focused upon investigating the intellectual space between the two approaches: seeking out the optimal blend of autonomy and maintaining humans in the loop via telepresence: co-exploration. In his recent NSF- INSPIRE project, spanning multiple NSF directorates (Computer and Information Science, Human Resources, Ocean Sciences), his team investigated how to make more effective use of telepresence in the pursuit of research and education as well as outreach. At one level, the project provided research opportunities for a cohort of early career scientists and their students to explore and investigate the deep ocean together, in real time, without ever leaving dry land. But at a higher level, the lessons learned, from the social scientists on the project, are of wider applicability across any distributed scientific network. Indeed, German’s expertise in this area has recently been included in a successful bid to NASA’s PSTAR program where he will serve as Deputy PI, investigating how the introduction of latency into telepresence-led investigations in the deep ocean could be used to prepare for future astronaut-led expeditions to the Moon and Mars. In parallel, his latest NOAA Ocean Exploration program funding is in the field of Co-Robotics, seeking to add further layers of autonomy to robots so that they can report back processed and analyzed data sets to science leads, via satellite, to accelerate decision making processes in the robotics-led exploration of remote oceans.

94 Donna K. Blackman [email protected] Research Geophysicist Scripps Institution of Oceanography UCSD, La Jolla, CA 92093-0225 Education Major Degree Yr Pasadena City College, Pasadena CA Geology A.A. 1979 University of California, Santa Cruz CA Earth Science B.S. 1982 Massachusetts Institute of Technology, Cambridge MA Marine Geophysics M. Sc. 1986 Brown University, Providence, RI Marine Geophysics PhD. 1991

Positions Held 7/03-present Research Geophysicist, Scripps Institution Oceanography, La Jolla CA 07/12-06/15 Program Director, National Science Foundation, OCE/MGG 8/95-7/96 Lecturer, Dept Earth Sciences, University of Leeds, Leeds, UK 5/92-6/03 Postdoc/Asst./Assoc. Research Geophysicists, Scripps Inst. of Oceanography 3/91-12/91 RIDGE Office admin., & research postdoc, University of Washington 8/80-8/83 Field/Lab Assistant, USGS, Pacific Marine Geology Branch, Menlo Park CA 11/78-6/79 Lab Assistant, Jet Propulsion Laboratory, Pasadena CA

Participation in geophysical/geological data acquisition during 24 research cruises since 1981, 3-8 wks each throughout the worlds oceans. Led/designed acquisition and sailed as chief scientist on 8 of these.

Professional & Synergistic Activities Editorial Board, Geophysical Journal International, 2017- Proposal review panels- Sweden (2014), Canada (2014, 2017), NASA (2016), NSF (8 during 1995-2012) IODP Science Planning Committee, Nov 2008-2012; SSEP 2001-2004 Ridge 2000, Chair 2005-2008, Steering Committee 2002-2005

Select Publications. Wei, S.S., D.A. Wiens, Y. Zha, T. Plank, S.C. Webb, D.K. Blackman, R.A. Dunn, J.A. Conder, Seismological evidence of effects of water on mantle melt transport beneath the Lau back-arc basin, Nature 518, doi:10.1038/nature14113, 2015. Blackman, D. K., A. Slagle, G. Guerin, & A. Harding , Geophysical signatures of past and present hydration within a young oceanic core complex, GRL 41, doi 10.1002/ 2013GL058111, 2014. Blackman, D.K., B. Ildefonse, B.E. John, Y. Ohara, D.J. Miller and Exp. 304/305 Science Party, Drilling Constraints on Lithospheric Accretion and Evolution at Atlantis Massif, Mid-Atlantic Ridge 30°N, J. Geophys. Res.116, B07103, doi:10.1029/2010JB007931, 2011. Blackman, D.K., J.P. Canales, and A. Harding, Geophysical signatures of oceanic core complexes, REVIEW ARTICLE Geophys. J. Int. 178, 593–613, doi: 10.1111/j.1365-246X.2009.04184.x, 2009. Blackman, D.K., Solid Earth Cycles & Geodynamics, Stein, R., D. Blackman, F. Inagaki, H-C. Larsen (editors), Earth and life processes discovered from subseafloor environments, Dev. Marine Geology 7, Elsevier, 10.1016/B978-0-444-62617-2.00016-5, 2014. Blackman, DK, RP von Herzen, LA Lawver, "Heat flow and tectonics in the western Ross Sea, Antarctica", in AK Cooper and FJ Davey (eds.), The Antarctic continental margin: geology and geophysics of the western Ross Sea, Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, vol. 5B, 179-189, 1987.

95 Andrew T. Fisher (Co-I) University of California, Santa Cruz (UCSC) Earth and Planetary Sciences Department 1156 High Street, Santa Cruz, CA 95064 831-459-5598

Experience Related to the Investigation: A. T. Fisher has >25 years of experience in marine hydrogeology and geothermics, with an emphasis on hydrothermal systems, including observational, laboratory, instrumentation, and numerical modeling studies. Fisher and his students and colleagues study coupled flows in the volcanic ocean crust, fluid-heat and fluid-solute transport, water/rock interaction, and links between fluid, chemical, and microbiological systems. Fisher is a co-PI for the NSF Science and Technology Center for Dark Energy Biosphere Investigations (C-DEBI).

Education: Ph.D. – Marine Geology and Geophysics, University of Miami, RSMAS – 1989 B.S. – Geology, Stanford University –1984

Appointments: Professor, Earth and Planetary Sciences Department, UC Santa Cruz, 2003-present Asso. Professor, Earth Sciences Department, UC Santa Cruz, 1999-03 Asst. Professor, Earth Sciences Department, UC Santa Cruz, 1995-99 Asso. Scientist, Geological Sciences Department, Indiana University, 1993-95 Staff Scientist and Adj. Asst. Professor, Ocean Drilling Program and Geophysics Department, Texas A&M University, 1989-93

Selected Honors/Awards: Distinguished Lecturer, International Ocean Discovery Program, 2016-17 E. O. Meinzer Award, Hydrogeology Division, Geological Society of America, 2016 Excellence in Teaching Award, University of California, Santa Cruz, 2012 Bennet Lecturer, University of Leicester, 2011 Fellow, Geological Society of America, 2006 NSF-RIDGE Distinguished Lecturer, 2003-04

Selected Related Publications (*student co-authors): • *Winslow, D. M., A. T. Fisher, P. H. Stauffer, C. W. Gable, and G. A. Zyvoloski (2016), Three- dimensional modeling of outcrop-to-outcrop hydrothermal circulation on the eastern flank of the Juan de Fuca Ridge, J. Geophys. Res., 121, 1365–1382, doi:10.1002/2015JB012606. • *Neira, N. M., J. F. Clark, A. T. Fisher, C. G. Wheat, R. M. Haymon, K. Becker, Cross-hole tracer experiment reveals rapid fluid flow in the upper ocean crust, Earth Planet. Sci. Lett. 450, 355-365, 10.1016/j.epsl.2016.06.048. 2016 • Fisher, A. T., K. D. Mankoff•, S. Tulaczyk, S. Tyler, N. Foley•, and the WISSARD Science Team (2015), High geothermal heat flux measured below the West Antarctic Ice Sheet, Science Advances, 1(6), doi:10.1126/sciadv.1500093. • *Winslow, D. M., and A. T. Fisher (2015), Sustainability and dynamics of outcrop-to-outcrop hydrothermal circulation, Nature Comm., 6, doi:10.1038/ncomms8567

96 ADDRESS Peter R. Girguis Harvard University Telephone: 617-496-8328 16 Divinity Avenue, room 3085 Fax: 617-495-8848 Cambridge, MA 02138-2020 E-mail: [email protected]

PROFESSIONAL TRAINING Monterey Bay Aquarium Research Institute (MBARI), Packard postdoc. fellow 2001-2004 Univ. of California, Santa Barbara, Ph.D. in Ecology, Evolution, and Marine Biology 2000 Univ. of California Los Angeles, B.Sc. in Marine Biology 1994

PROFESSIONAL AFFILIATION / APPOINTMENTS Professor of Organismic and Evolutionary Biology, Harvard University 2013-present John L. Loeb Associate Professor of Natural Sciences, Harvard University 2009-2013 Assistant Professor, Harvard University 2005-2009 Adjunct Research Engineer, MBARI 2005-2012

RELEVANT PUBLICATIONS (of 87 peer-reviewed publications) Tang, T., Mohr, W., Sattin, S.R., Rogers, D.R., Girguis, P.R. and Pearson, A. 2017. Geochemically- distinct carbon isotope distributions in Allochromatium vinosum DSM 180T grown photoautotrophically and photoheterotrophically. Geobiology 15(2): 324-339. Bradley, A.S., Leavitt, W.D., Schmidt, M., Knoll, A.H., Girguis, P.R. and Johnston, D.T. 2016. Patterns of sulfur isotope fractionation during sulfate reduction. Geobiology, 14(1):91-101. Picard, A., Gartman, A. and Girguis, P.R., 2016. What do we really know about the role of microorganisms in iron sulfide mineral formation? Frontiers in Earth Science, 4, p.68. Sperling, E. A., Knoll, A. H., & Girguis, P. 2015. The Ecological Physiology of Earth’s Second Oxygen Revolution. Annual Review of Ecology, Evolution, and Systematics, 46(1). Orcutt, B. N., Sylvan, J. B., Rogers, D. R., Delaney, J., Lee, R. W., & Girguis, P. R. 2015. Carbon fixation by basalt-hosted microbial communities. Frontiers in Microbiology, 6. DOI:10.3389/fmicb.2015.00904 Bose, A., Vidoudez, C., Parra, E.A., Gardel, E.J., and Girguis. P.R. 2014. Electron uptake by Rhodopseudomonas palustris TIE-1. Nature Communications. doi:10.1038/ncomms4391 Schrader, P.S., Reimers, C.E., Girguis, P., Delaney, J., Doolan, C., Wolf, M. and Green, D. 2016. Benthic Microbial Fuel Cells Powering Sensors and Acoustic Communications with the MARS Underwater Observatory. Journal of Atmospheric and Oceanic Technology, 33(3), pp.607-617. Wankel, S.D., Huang, Y., Gupta, M., Provencal, B., Leen, J.B., Fahrland, A., Vidoudez, C., and Girguis, P.R. 2013. Characterizing the distribution of methane sources and cycling in the deep sea via a new in situ stable isotope analyzer. Environmental Science and Technology. doi: 10.1021/es303661w Rabaey, K., Girguis, P.R., and Nielsen, L.K. 2011. Metabolic and practical considerations on microbial electrosynthesis. Current Opinion in Biotechnology, 22: 1-7. doi:10.1016/j.copbio.2011.01.010 Girguis, P.R., Nielsen, M.E. and Figueroa, I. 2010. Harnessing energy from marine productivity using bioelectrochemical systems. Current Opinion in Biotechnology, 21(3): 252-258. doi:0.1016/j.copbio.2010.03.015

97 Dr. Kevin Peter Hand Jet Propulsion Laboratory, 4800 Oak Grove Drive • Pasadena, CA 91109 (626) 487-5379 Kevin P. Hand is a planetary scientist at JPL working on numerical modeling, laboratory investigations, missions, and field campaigns related to the physics, chemistry, and habitability of ocean worlds.. EDUCATION Ph.D., Geological & Environmental Sciences, Stanford University, Stanford, CA. (2007) M.S., Mechanical Engineering, focus on robotics (2002), Stanford University, Stanford, CA. B.A. Physics, with minor in Astronomy (1998), Dartmouth College, Hanover, New Hampshire. SELECT PROFESSIONAL EXPERIENCE, SERVICE, AND AWARDS: . Pre-Project Scientist, Europa Lander for Surface Astrobiology (Pre-Phase A), May 2016-present. . Deputy Chief Scientist for Solar System Exploration (4x), JPL, Oct. 2011-May 2016. . United States Navy, Strategic Studies Group, Advisor/Lecturer, Nov. 2013 . X-Prize Foundation, Advisory Council on Space and Exploration, 2013-present . 2011 National Geographic Emerging Explorer . Kavli Frontiers of Science Scholar 2007, 2011 . Europa Flagship Mission Science Definition Team (2007, 2008, 2011 studies). SELECT PUBLICATIONS Trumbo, S. K., Brown, M. E., Fischer, P. D., & Hand, K. P. (2017). A New Spectral Feature on the Trailing Hemisphere of Europa at 3.78 μm. The Astronomical Journal, 153(6), 250. Nordheim, T. A., Hand, K. P., Paranicas, C., Howett, C. J. A., Hendrix, A. R., Jones, G. H., & Coates, A. J. (2017). The near-surface electron radiation environment of Saturn's moon Mimas. Icarus. Vance, S. D., Hand, K. P., & Pappalardo, R. T. (2016). Geophysical controls of chemical disequilibria in Europa. Geophysical Research Letters, 43(10), 4871-4879. Sparks, W. B., Hand, K. P., McGrath, M. A., Bergeron, E., Cracraft, M., & Deustua, S. E. (2016). Probing for evidence of plumes on Europa with HST/STIS. The Astrophysical Journal, 829(2), 121. Fischer, P. D., M. E. Brown, K. P. Hand (2015) Spatially Resolved Spectroscopy of Europa: The Distinct Spectrum of Large-scale Chaos. The Astronomical Journal. C. L. Young, J. J. Wray, R. N. Clark, J. R. Spencer, D. E. Jennings, K. P. Hand, M. J. Poston, and R. W. Carlson (2015) Silicates on Iapetus from Cassini’s CIRS. Astrophys. J. Lett. 811, L27. Carlson, R.W. and Hand, K.P. (2015) Radiation Noise Effects at Jupiter’s Moon Europa: In-situ and Laboratory Measurements and Radiation Transport Calculations. Trans Nuc. Sci. Hand, K.P. & Carlson, R.W (2015) Europa's surface color indicates an ocean rich with NaCl. GRL. 3174. Matheus Carnevali, P.,…Love, G.D., Priscu, J.C…Hand, K.P., Muray, A.E. (2015) Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska. Geobiology. Hand, K.P. and Brown, M.E. (2013) Keck II Observations of Hemispherical Differences in H2O2 on Europa. The Astrophysical Journal Letters, 766:2, L21, doi:10.1088/2041-8205/766/2/L21. Brown, M.E. and Hand, K.P. (2013) Salts and Radiation Products on the Surface of Europa. The Astronomical Journal, 145:4, 110, doi:10.1088/0004-6256/145/4/110. Hand, K.P. and Carlson, R.W. (2012) Laboratory spectroscopic analyses of electron irradiated alkanes and alkenes in solar system ices J. Geophys. Res., 117, E03008, doi:10.1029/2011JE003888. Hand, K.P. and Carlson, R.W. (2011) H2O2 production by high-energy electrons on icy satellites as a function of surface temperature and electron flux. Icarus. doi:10.1016/j.icarus.2011.06.031 Hand, K. P., K. K. Khurana, and C. F. Chyba (2011), Joule heating of the south polar terrain on Enceladus, J. Geophys. Res., 116, E04010, doi:10.1029/2010JE003776. Hand, K.P. (2010) The ocean of Europa and implications for habitability and the origin of life. Astrobiology: from simple molecules to primitive life. Eds. V.A. Basiuk & R. Navarro-Gonzalez. Hand, K.P., Chyba, C.F., J.C. Priscu, Carlson, R.W. & K.H. Nealson (2009) Astrobiology and the Potential for Life on Europa. In Europa. Eds. R. Pappalardo, W. McKinnon, & K. Khurana. UAP. Hand, K.P., Carlson, R. W., & Chyba, C. F. (2007) Energy, chemical disequilibrium, and geological constraints on Europa. Astrobiology. 7:6, 1-18. Hand, K. P., Carlson, R. W., Cooper, J., & Chyba, C. F. (2006) Clathrate hydrates of oxidants in the ice shell of Europa. Astrobiology. 6:3, 463-482. Chyba, C.F. and Hand, K.P. (2001) Life without Photosynthesis. Science 292, 2026-2027.

98 Tori Hoehler (Co-I) Space Sciences & Astrobiology Division NASA Ames Research Center Mail Stop 239-4 Moffett Field, CA 94035 650-604-1355

Experience Related to the Investigation: Tori Hoehler is a chemist with > 20 years experience in quantifying the relationship between energy availability and biological activity through observational, experimental, and theoretical approaches. He served on the science definition teams for the Europa Clipper and Lander mission concepts, was a collaborating scientist on the MSL (Curiosity) mission, and was the astrobiology representative to the MEPAG Goals Committee for 8 years. Education: Ph.D. in Marine Chemistry, University of North Carolina at Chapel Hill, 1998 B.S. in Chemistry with Highest Honors and Highest Distinction, University of North Carolina at Chapel Hill, 1992 Appointments: Research Scientist, Space Sciences & Astrobiology Division, NASA Ames Research Center (2001-present) Honors/Awards: NASA Exceptional Scientific Achievement Medal (2015); NASA Ames Honor Awards for Excellence in Education and Outreach (2014) and Research (2009); Carl Sagan Lecturer, American Geophysical Union (2009); Kavli/NAS Fellow (2007); Fellow of the California Academy of Sciences (2007) Related publications: Hoehler, TM and BB Jørgensen (2013) Microbial life under extreme energy limitation, Nature Reviews Microbiology, 11, 83-94. Alperin, MJ and TM Hoehler (2010) The ongoing mystery of seafloor methane, Science, 329, 288-289. Hoehler, TM, RP Gunsalus, and MJ McInerney (2010) Environmental constraints that limit methanogenesis, in Handbook of Hydrocarbon and Lipid Microbiology, KN Timmis (Ed.), Springer-Verlag, Berlin, pp 636-654. Hoehler, TM (2007) An energy balance concept of habitability, Astrobiology, 7, 824-838. Hoehler, TM (2004), Biological energy requirements as quantitative boundary conditions for life in the subsurface, Geobiology, 2, 205-215. Hoehler, TM, MJ Alperin, DB Albert, and CS Martens (2001), Apparent minimum free energy requirements for methanogenic archaea and sulfate-reducing bacteria in an anoxic marine sediment. FEMS Microbiology Ecology, 38(1), 33-41. Hoehler, TM, MJ Alperin, DB Albert, and CS Martens (1998), Thermodynamic controls on hydrogen concentrations in anoxic sediments, Geochimica et Cosmochimica Acta, 62, 1745- 1756.

99 Julie A Huber (Co-I) Marine Chemistry and Geochemistry Woods Hole Oceanographic Institution 266 Woods Hole Road, MS #51 Woods Hole, MA 02543 508-289-2556

Experience Related to the Investigation: J. Huber has over 15 years of experience as a deep-sea microbiologist. Her research program investigates subseafloor microbial ecosystems in oceanic crust to resolve the extent, function, evolutionary dynamics, and biogeochemical impact of the deep marine biosphere. She serves as Associate Director of the NSF Science and Technology Center for Dark Energy Biosphere Investigations (C-DEBI), focused on subseafloor life.

Education: B.Sc. – Marine Science, Eckerd College –1998 M.Sc., – Ph.D. Biological Oceanography, Univ. of Washington –2002, 2004 Certificate in Astrobiology, Univ. of Washington – 2004

Appointments: National Research Council Research Associate, NASA Astrobiology Institute, 2005-2007 Assistant Scientist, Bay Paul Center, MBL, 2007-2012 Associate Scientist and Director, Bay Paul Center, MBL, 2012-2017 Associate Scientist w/ Tenure, Marine Chemistry & Geochemistry, WHOI, 2017-present

Honors/Awards: National Research Council Research Associateship Award, NASA Astrobiology – 2004 L’Oréal USA Fellowship for Women In Science – 2007 NSF-RIDGE Distinguished Lecturer – 2008 Neal Cornell Career Development Award, MBL – 2010 Kavli Fellow – 2017

Selected Related Publications (*student/post-doc co-authors): • *Fortunato, C.F. and J.A. Huber. 2016. Coupled RNA-SIP and metatranscriptomics of active chemolithoautotrophic communities at a deep-sea hydrothermal vent. ISME J. 10:1925-1938 • *Reveillaud, J., Reddington, E., *McDermott, J., *Meyer, J.L., *Algar, C., Sylva, S., Seewald, J., German, C.G., and J.A. Huber. 2016. Subseafloor microbial communities in hydrogen-rich vent fluids from hydrothermal systems along the Mid-Cayman Rise. Environ Micro. 18:1970–1987. • *Meyer, J.L, Jaekel, U., *Tully, B. Glazer, B.T., Wheat, C.G., H-T, Lin., C-C, Hsieh, Cowen, J.P., Hulme, S.M., Girguis, P.R., and J.A. Huber. 2016. A distinct and active bacterial community in cold oxygenated fluids circulating beneath Mid-Atlantic seafloor. Sci Reports. 6:22541; doi: 10.1038/srep22541 • *Meyer, J.L. and Huber, J.A. 2014. Strain-level genomic variation in natural populations of Lebetimonas from an erupting deep-sea volcano. ISME J. 8: 867–880.

100 Vita: John Charles Marshall Cecil and Ida Green Professor of Oceanography, MIT

Address Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology Cambridge, MA 02139-4307, USA email: [email protected] http://oceans.mit.edu/JohnMarshall/

Education Scholarship to Imperial College, London (1973) B.Sc. in Physics (1st Class Hons), Imperial College (1976) Ph.D. in Atmospheric Sciences, Imperial College (1980)

Employment Postdoctoral Researcher, Imperial College (1981) Postdoctoral Researcher, Oxford University (1982-83) Lecturer, Department of Physics, Imperial College (1984-89) Reader, Department of Physics, Imperial College (1989-1991) Associate Professor, Massachusetts Institute of Technology (1991-1992) Professor, Massachusetts Institute of Technology (1993-2009) Cecil and Ida Green Professor of Oceanography at MIT (2009 – present)

Research Interests I am an oceanographer with broad interests in climate and the general circulation of the atmosphere and oceans, which I study through the development of mathematical, numerical and laboratory models of key physical and biogeochemical processes. Research interests include: general circulation of the ocean, ocean convection and thermohaline circulation, ocean gyres and circumpolar currents, geophysical fluid dynamics, the role of the ocean in climate, numerical modeling of ocean and atmosphere.

Author or coauthor of about 170 refereed publications. Coauthor of an undergraduate text book (with Alan Plumb) entitled: Atmosphere, ocean and climate dynamics: an introductory text. Academic Press, 2008.

Mentoring of graduate students and post-doctoral researchers Some 21 students have earned their Ph.D.’s under my direct supervision and I have also worked with 29 young scientists during their postdoctoral studies.

Leadership roles in NASA science I was a lead PI on the initial Earth System Modeling Framework (ESMF) proposal which put in place a software modeling infrastructure for climate modeling. I was the PI of the ECCO2 project which, working with my colleague Carl Wunsch of MIT, has pioneered the field of ocean state estimation for climate science. Currently I am closely collaborating with the ocean modeling group at GISS in the context of climate change research and ocean model development.

101 Jeffrey Seewald Department of Marine Chemistry & Geochemistry Woods Hole Oceanographic Institution Woods Hole, MA 02332 Experience Relevant to the Investigation Implementation of a research program that uses field, laboratory, and theoretical approaches to examine fluid-rock-sediment reactions in geological environments with a focus on chemical processes that regulate the generation and stability of aqueous organic compounds. Extensive experience in the application of laboratory experiments to examine organic-inorganic interactions under hydrothermal conditions.

Education Ph.D., Geology, 1990, University of Minnesota, Minneapolis, MN M.Sc., Geology, 1987, University of Minnesota, Minneapolis, MN B.A., Geology, 1984, Colgate University, Hamilton, NY

Appointments Senior Scientist, Woods Hole Oceanographic Institution, 2008 to present Education Coordinator, Marine Chemistry and Geochemistry Department, WHOI, 2017- Chair, Marine Chemistry & Geochemistry Dept., WHOI, 2010 to 2014 Associate Scientist with tenure, Woods Hole Oceanographic Institution, 2001 to 2008 Associate Scientist, Woods Hole Oceanographic Institution, 1996 to 2001 Assistant Scientist, Woods Hole Oceanographic Institution, 1992 to 1996 Postdoctoral Investigator, Woods Hole Oceanographic Institution, 1991 to 1992 Postdoctoral Scholar, Woods Hole Oceanographic Institution, 1990 to 1991

Honors/Awards J. Seward Johnson Chair in Oceanography, WHOI, 2017 to 2020. Stanley W. Watson Chair for Excellence in Oceanography, WHOI, 2015 to 2018 Fellow, Hanse-Wissenschaftskolleg, Delmenshorst, Germany, 2009-2010 Best Paper in Organic Geochemistry for 1994, Geochemical Society

Relevant Publications (#student or postdoc advised by JSS) #McNichol J., Sylva S.P., Thomas F., Taylor C.D., Sievert S.M., Seewald J.S. (2016) Assessing microbial processes in deep-sea hydrothermal systems by incubation at in situ temperature and pressure. Deep Sea Research Part 1 115, 221-232. #McDermott J.M., Seewald J.S., German C.R., Sylva S.P. (2015) Pathways for abiotic organic synthesis at submarine hydrothermal fields. Proc. Nat. Acad. Sci. 112, 7668-7672. Seewald J.S., Reeves E.P., Bach W., Saccocia P.J, Craddock P.R., Shanks W.C. III, Sylva S.P., Pichler T., Rosner M., and Walsh E. (2015) Submarine venting of magmatic volatiles in the Eastern Manus Basin, Papua New Guinea. Geochim. Cosmoshim. Acta 163, 178-199. McCollom T.M., Seewald J.S., German C.R. (2015) Investigation of Non-volatile Organic Compounds in Deep-sea Hydrothermal Vent Fluids along the Mid-Atlantic Ridge. Geochim. Cosmoshim. Acta 156, 122-144. #Reeves E.P., McDermott J.M., Seewald J.S. (2014) The origin of methanethiol in mid-ocean ridge hydrothermal fluids. PNAS, doi:10.1073/pnas.1400643111. #Proskurowski, G., Lilley, M.D., Seewald, J.S., Olson, E.J., Früh-Green, G.L., Lupton, J.E., Sylva, S.P., Kelley, D.S. (2008) Abiogenic Hydrogen and Hydrocarbon Production at the Lost City Hydrothermal Field. Science 319, 604-607. McCollom T.M. & Seewald J.S. (2007) Abiotic synthesis of organic compounds in deep-sea hydrothermal environments. Chemical Reviews 107, 382-401. Seewald J.S., Zolotov M., McCollom T.M. (2006) Experimental investigation of carbon speciation under hydrothermal conditions, Geochim. Cosmochim. Acta 70, 446-460. Seewald J.S. (2001) Aqueous geochemistry of low molecular weight hydrocarbons at Elevated temperatures and pressures: constraints from mineral buffered laboratory experiments. Geochim. Cosmochim. Acta 65, 1641-1644.

102 Everett L Shock (Co-I) School of Earth & Space Exploration, and School of Molecular Sciences Arizona State University, Tempe, AZ, 85287 480-965-0631 Experience Related to the Investigation: E. Shock studies planetary habitability through the lens of geochemistry, building theoretical methods to predict the consequences of water-rock reactions and organic compound stabilities over wide ranges of temperature and pressure, testing predictions with hydrothermal experiments, and following the energy flow through serpentinizing and hydrothermal ecosystems. He is a co-investigator on the MASPEX- Europa team that will supply the mass spectrometer for NASA’s Europa Clipper mission and interpret the molecular and isotopic data it obtains. Education: B.Sc. – Earth Sciences, UC Santa Cruz –1978 Ph.D. – Geology, UC Berkeley –1987 Appointments: Co-Director, Environmental Life Sciences Graduate Program, ASU (2013-2017). Professor, School of Earth & Space Exploration and School of Molecular Sciences, ASU (since 2002). Director, W.M. Keck Foundation Laboratory for Environmental Biogeochemistry, ASU (since 2002). Director, Environmental Studies Program, Washington University, St. Louis, MO, USA (1993-2001). Professor, Associate Professor, and Assistant Professor, Department of Earth and Planetary Sciences, Washington University, St. Louis, MO, USA: (1987-2002). Honors/Awards: Designation of a hyperthermophilic archeon as Thermogladius shockii, 2011 Fellow, Geochemical Society and European Association for Geochemistry, 2009 Steinbach Scholar, Woods Hole Oceanographic Institution, 2007 Fellow, American Geophysical Union, 2005 Hooker Distinguished Visiting Professor, McMaster University, 2004 Selected Related Publications (*student co-authors): Amenabar MJ, Shock EL, Roden EE, Peters JW, Boyd ES (2017) Energy demand, not supply, dictates microbial substrate preference. Nature Geoscience (in press). *Canovas PC III, Hoehler T, Shock EL (2017) Geochemical bioenergetics during low-temperature serpentinization: An example from the Samail ophiolite, Sultanate of Oman. Jour. Geophys. Res. - Biogeosciences (in press). *Glein CR Shock, E.L. (2010) Sodium chloride as a geophysical probe of a subsurface ocean on Enceladus. Geophysical Research Letters L09204, doi:10.1029/2010 GL042446. *Glein C, Shock EL (2013) A geochemical model of non-ideal solutions in the methane-ethane-propane- nitrogen-acetylene system on Titan. Geochim. Cosmochim. Acta 115, 217-240. *Neveu M, Desch SJ, Shock EL, Glein CR (2015) Prerequisites for explosive cryovolcanism on dwarf planet-class Kuiper belt objects. Icarus 246, 48-64. Shock EL, Boyd ES (2015) Principles of geobiochemistry. Elements 11, 395-401. Venturi S, Tassi F, Gould IR, Shock EL, Hartnett HE, Lorance ED, Bockisch C, Fecteau K, Capecchiacci F, Vaselli O (2017) Mineral-assisted production of benzene under hydrothermal conditions: insights from experimental studies on C6 cyclic hydrocarbons. Jour. Volc. Geothermal Res. (in press). *Yang Z, Hartnett HE, Shock EL, Gould IR (2015) Organic oxidations using geomimicry. J. Org. Chem. 80, 12159-12165. *Yang Z, Williams LB, Hartnett HE, Gould IR, Shock EL (2017) Effects of iron-containing minerals on hydrothermal reactions of ketones. Geochim. Cosmochim. Acta (submitted).

103 Christophe Sotin (Co-I) Chief Scientist for Solar System Exploration Jet Propulsion Laboratory 4800 Oak Grove Drive • M/S 321-625 Pasadena, CA 91109, (818) 354-3264

Investigator Roles Will provide models of the interior structure and dynamics of the silicate layer at the interface with the ocean (Investigation 1: Rocky Interiors Geophysics) and will participate in Investigations 2 and 3.

Experience Related to the Investigation Christophe Sotin has over 30 years of experience in planetary science including the Earth. His interests include the simulation of internal processes. He has worked on the interior structure and dynamics of Earth-like planets and icy moons. He has co-authored more than 200 papers in refereed journals and books, including papers dealing with mid-ocean ridges. He is a team member of the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini mission. He was appointed as Chief Scientist for Solar System Exploration at JPL in 2012.

Education • 11/86: Docteur d'Etat ès Sciences at Paris VII University • 09/83: Ph.D. in Geophysics at Institut de Physique du Globe de Paris • 06/81: D.E.A. (Master degree in Science) in Geophysics at Nancy University • 06/81: Master Degree in Geological Engineering from Ecole Nationale Supérieure de Géologie

Honors/Awards Asteroid 54963 named Sotin (February 2012) 2008 recipient of the Runcorn-Florensky medal of the European Geosciences Union 4 NASA team awards and 2 ESA team awards

Related Publications Hussmann, H., Sotin, C., and Lunine, J. (2015) Interiors and evolution of icy satellites, in ‘Treatise in Geophysics’, Schubert et al. (eds), vol. 10: Planets and Moons, Elsevier. Sotin, C., Tobie, G., Wahr, J., and McKinnon, W. B. (2009) Tides and Tidal Heating on Europa; in Europa, Pappalardo R. et al. (Eds), University of Arizona Space Science Series, 85-117. Tobie G., O. Cadek and C. Sotin (2008) Solid tidal friction above a liquid water reservoir as the origin of the south pole hotspot on Enceladus; Icarus, 196, 642–652. Sotin, C. and Prieur, D. (2007)Jupiter’s moon Europa: Geology and Habitability; In ‘Complete Course in Astrobiology’, G. Horneck & P. Rettberg (Eds.), Wiley-VCH, 253-271. Sotin C. and Tobie G., (2004), Internal structure and dynamics of the large icy satellites, C. R. Acad. Sci. Physique, 5, 769-780. Parmentier EM, Sotin C, Travis BJ (1994) Turbulent 3D thermal convection in an infinite Prandtl number, volumetrically heated fluid : implications for mantle dynamics, Geophys. J. Int, 116: 241-251. Sotin C , Parmentier EM (1989) Dynamical consequences of compositional and thermal density stratification beneath spreading centers, Geophys. Res. Lett., 16, 835-838.

104 Andreas M Thurnherr (Co-I) Division of Ocean and Climate Physics Lamont-Doherty Earth Observatory of Columbia University 61 Route 9W Palisades, NY 10964 845-365-8816

Experience Related to the Investigation: A. Thurnherr is an observational physical oceanographer interested in how the ocean works. His most important research interests concern processes acting near topography, hydrothermal circulation, horizontal and vertical dispersal, as well as the large-scale circulation. He has more than 20 years of experience working with oceanographic data, models as well as theory, in particular in the context of interdisciplinary projects.

Education: Ph.D., Physical Oceanography, 2000, Southampton University, Southampton, UK M.Sc., Oceanography, 1996, Southampton University, Southampton, UK Dipl. Ing., Computer Science and Engineering, 1992, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland

Appointments: Lamont Research Professor, LDEO OCP, 2013 to present Adjunct Scientist, WHOI AOPE, 2013 to present Lamont Associate Research Professor, LDEO OCP, 2010-2013 Doherty Research Scientist, LDEO OCP, 2010 Doherty Associate Research Scientist, LDEO OCP, 2003-2010 Research Faculty, FSU Oceanography, 2002-2003 Postdoctoral Researcher, FSU Oceanography, 2000-2002 UNIX Instructor, Digicomp AG, Zürich, 1994-2000 Scientific Assistant, Swiss National Supercomputing Center, 1993 Scientific Assistant, Supercomputing Center of ETH Zürich, 1991-1993 Systems Engineer, Abakus AG, Zürich, 1987-1989 Systems Engineer, Data General, Zürich, 1986-1987 Software Developer, Alfasoft, Rapperswil, 1984-1987

Relevant Publications: Thurnherr, A. M., J. R. Ledwell, J. W. Lavelle, and L. S. Mullineaux (2011). Hydrography and circulation near the crest of the East Pacific Rise between 9◦ and 10◦N. Deep Sea Res. 58, 365–376. Adams, D. K., D. J. McGillicuddy, L. Zamudio, A. M. Thurnherr, X. Liang, O. Rouxel, C. R. German, and L. S. Mullineaux (2011). Surface-generated mesoscale eddies transport deep-sea products from hydrothermal vents. Science 332, 580–583. Jackson, P. R., J. R. Ledwell, and A. M. Thurnherr (2010). Dispersion of a tracer on the East Pacific Rise (9◦N to 10◦N), including the influence of hydrothermal plumes. Deep Sea Res. I 57, 37–52. Thurnherr, A. M., G. Reverdin, P. Bouruet-Aubertot, L. St. Laurent, A. Vangriesheim, and V. Ballu (2008). Hydrography and flow in the Lucky Strike segment of the Mid-Atlantic Ridge. J. Mar. Res. 66, 347–372. Thurnherr, A. M. and K. J. Richards (2001). Hydrography and high-temperature heat flux of the Rainbow hydrothermal site (36◦14′N, Mid-Atlantic Ridge). J. Geophys. Res. 106, 9411–9426.

105 NASA High End Computing

Pre-Request

HEC Request Number: HEC-SMD-17-1183

Computing Request Title: Exploring Ocean Worlds

Division: Planetary Science

PI Name: German Christopher

Co-Investigator(s): Tori Hoehler Everett Shock

Funding Manager(s): Mary Voytek

Organization Name: ARC

Organization Type: NASA

Period of Performance (Months): 60

Justification: The project's goal is to investigate the potential habitability of Ocean Worlds like Jupiter's moon Europa and Saturn's moon Enceladus. We anticipate creating a database that associates biosynthetic potential with a range of potentially observable parameters in these oceans. These observable parameters are quantified here using a program called EQ3/6, which simulates the reaction of water with rock. We want to use Pleiades as we anticipate running the software 1e7 times to explore a large parameter space of water and rock compositions. The ability of Pleiades to run GNU Parallel will enable us the complete dataset to be created and analyzed within the period of performance. SBUs and Storage:

Year SBUs Requested Storage Requested 1 500 1

2 500 1

3 500 1

4 500 1

5 500 1