The Importance of Field Studies for Closing Key Knowledge Gaps in Planetary Science

White paper for the 2023–2032 Decadal Survey on Planetary Science and Astrobiology by the National Academies of Science / Engineering / Medicine

Authors (Content contributors, editors, and supporters)

Patrick L. Whelley, (patrick.l.whelley@nasa.gov, 410-206-7362) University of Maryland - NASA Goddard; Cherie N. Achilles, NASA Goddard; Alice M. Baldridge, Saint Mary’s College of CA & The Planetary Science Institute; Maria E. Banks, NASA Goddard; Ernest Bell, University of Maryland; Hannes Bernhardt, Arizona State University; Janice Bishop, SETI Institute; Jennifer G. Blank, NASA Ames; Dina M. Bower, University of Maryland; Shane Byrne, University of Arizona; Jaclyn Clark, Arizona State University; David A. Crown, Planetary Science Institute; Larry S. Crumpler, New Mexico Museum of Natural History and Science; Sean Czarnecki, Arizona State University; Ashly Davies, Jet Propulsion Laboratory; Andrew de Wet, Franklin & Marshall College; Jake W. Dean, Arizona State University; Steven Dibb, Arizona State University; Chuanfei Dong, Princeton University; Lauren A. Edgar, USGS Astrogeology Science Center; Sarah Fagents, University of Hawaiʻi at Mānoa; Timothy D. Glotch, Stony Brook University; Timothy A. Goudge, The University of Texas at Austin; Alison H. Graettinger, University of Missouri-Kansas City; Trevor G. Graff, NASA Johnson; Amber L. Gullikson, USGS Astrogeology Science Center; Christopher W. Hamilton, University of Arizona; Casey I. Honniball, NASA Goddard; Kevin Hubbard, Arizona State University; Laura Kerber, NASA Jet Propulsion Laboratory; Laszlo Kestay (Keszthelyi), USGS Astrogeology Science Center; Shannon Kobs-Nawotniak, Idaho State University; Melissa D. Lane, Fibernetics LLC; Graham Lau, Blue Marble Space Institute of Science; Emily Law, NASA Jet Propulsion Laboratory; Einat Lev, Lamont-Doherty Earth Observatory; Alexandra Matiella-Novak, Johns Hopkins APL; Amy McAdam, NASA Goddard; Jeffrey E. Moersch, University of Tennessee, Knoxville; Catherine Neish, The University of Western Ontario & The Planetary Science Institute; Gordon Osinski, The University of Western Ontario; Rutu Parekh, DLR Institute of Planetary Science; Kristen Paris, Arizona State University; Edward L. Patrick, Southwest Research Institute; Elizabeth Rampe, NASA Johnson; Jacob Richardson, University of Maryland - NASA Goddard; Rodrigo Romo, Pacific International Space Center for Exploration Systems; M. Elise Rumpf, USGS Astrogeology Science Center; Kirby Runyon, Johns Hopkins, APL; Alicia M. Rutledge, Northern Arizona University; Stephen P. Scheidt, Howard University; Nicholas Schmerr, University of Maryland; Steven Semken, Arizona State University; Brian Shiro, USGS Hawaii Volcano Observatory; Everett L. Shock, Arizona State University; John Roma (J.R.) Skok, SETI Institute; Sarah S. Sutton, University of Arizona; Jessica Swann, Arizona State University; Michael T. Thorpe, NASA Johnson; Ingrid A. Ukstins, University of Iowa; Paul J. van Susante, Michigan Technological University; Nicole Whelley, University of Maryland - NASA Goddard; David A. Williams, Arizona State University; R. Aileen Yingst, Planetary Science Institute; Kelsey Young, NASA Goddard; Jon Zaloumis, Arizona State University; James R. Zimbelman, National Air and Space Museum, Smithsonian Institution; Co-signed by the Goddard Instrument Field Team (GIFT) 1. The Role of Field Based Studies in Planetary Science Field based studies (i.e., fieldwork) provide unique and essential perspectives on planetary processes. Our basic understanding of planetary bodies is primarily derived from our understanding of Earth as a planet. Scientific examination of geological features and active processes on Earth provides the critical ground truth that enables scientists to infer processes from products in other planetary systems. Where aspects of the environment or physical process are similar, scientists are able to learn about planetary systems through analogy. In the preface of their 2011 Geological Society of America Special Paper on planetary analog field sites, the authors put it this way:

“Historically, there has been an instinctive nature to use aspects of Earth to explain observations of other planets and moons; from early descriptions of areas on the moon resembling “seas” and “oceans” to the interpretation of “canals” on Mars. If we look closely, our own planet can serve as a Rosetta Stone or analog for understanding the geology in the solar system.” (Garry and Bleacher, 2011)

Writing about Earth-based analogs to Mars in a 2007 book, the author argues for the utility of terrestrial analogs that can be extrapolated to other terrestrial surfaces:

“It is necessary and cost effective to attempt to be certain that our mission instruments and personnel are equipped and trained to detect and discern the nature of Martian terrains before they are deployed on that planet. Therefore, research geologists investigate terrestrial analog environments to develop criteria to better identify the nature of planetary deposits from remote surface measurements and orbiting spacecraft data.” (M. Chapman, 2007)

Analog fieldwork allows scientists to take advantage of the complexity found in natural systems to learn about the fundamental processes that have shaped planetary bodies and their habitability throughout the solar system and beyond and to improve and enhance the science return of planetary missions. Analog fieldwork is relatively low-cost, easy access and low-risk platform which provides a testing ground to mature and validate on board instruments, engineering requirements, technology, and scientific field methods. Analog locations can be used to identify and overcome challenges before missions, troubleshoot off-nominal situations during missions, and understand challenges after missions’ end. Field studies allow for the development of robust operational exploration plans and strategies which then serve as a base to design future planetary missions. Finally, analog field studies provide opportunities to engage the public, promote space exploration, and recruit and train future colleagues.

2. Prior NASA funding of planetary analog fieldwork Analog fieldwork has been an important part of studying modern planetary science for decades. Eugene (Gene) Shoemaker, the founder of planetary geology, was an avid field geologist and advocated for locating the USGS Astrogeology Branch in Flagstaff, Arizona in the 1960s (Chapman, 1997) amongst important examples of volcanic features, impact structures, sedimentary and structural geological wonders. During the Apollo program, locations such as 1 those found in Arizona, Hawaii, Nevada (and elsewhere) were used extensively to train the crews in collecting soil samples, rock specimens and to test geological tools. These sites provided geological and geophysical conditions which were expected to be similar to those on the surface of the Moon. NASA funded studies of impact structures (including Meteor Crater in northern Arizona), solidified the recognition of lunar craters for impact features (Levy, 2002), and paved the way for comparisons of other geological processes between the Earth and terrestrial planets. Comparative planetology that builds on NASA funded analog studies is now commonplace in a variety of geology subdisciplines. For example, Hawaiian shield volcanoes and basaltic volcanic features of the eastern Snake River Plain are studied extensively as analogs to martian features because of similarities in composition, structural features, and morphology (e.g., Greeley and King, 1977; Carr and Greeley, 1980; Mouginis-Mark et al., 2007). Terrestrial lava tubes are considered possible analogs to lunar sinuous rilles because of their similar morphology and provenance (Greeley, 1971). Volcanic domes on Earth provide models for venusian domes because of their similar morphology (e.g., Pavri et al., 1992; Stofan et al., 2000). The hyper-arid Atacama Desert is the focus of studies to understand the potential of the martian sub-surface to support life (e.g., McKay et al., 2004). Arctic and Antarctic ice shelves are used as analogs to the surface of Europa for a variety of astrobiological, geophysical and ice mechanics studies (e.g., Bulat et al., 2011). These are just a few examples of the many possible ways field studies increase our understanding of geological and biological processes in the Solar System. Over the past decade, NASA’s Planetary Science strategic objective has been to “advance scientific knowledge of the origin and history of the solar system, the potential for life elsewhere, and the hazards and resources present as humans explore space” (Vision and Voyages for Planetary Science in the Decade 2013–2022). Analog field science is key to addressing these objectives, and NASA’s Research Opportunities in Space and Earth Science (ROSES) programs specifically solicit such work (Table 1).

Table 1: Selected NASA Science Mission Directorate proposals with a significant field component*

2014 2015 2016 2017 2018 2019 2020 Selected SSW: number 5 (6) 2 (3) 5 (8) 8 (11) 3 (4) Selections pending Proposals with a (percentage of selected) significant field PSTAR: number ° 7 8 6 6 0† 4 0† component* Total: number 12 10 11 14 3 4 (Incomplete) Data were tabulated from “Abstracts of Selected Proposals” [nspires.nasaprs.com]. * These are proposals where the field component was mentioned in the publicly available abstract. ° All proposals, per requirement, have a field component in PSTAR, only the number is given † Not solicited

Since 2014, two of the main programs in ROSES that have had calls for analog fieldwork are the Solar System Workings Program (SSW) and Planetary Science and Technology Through Analog Research (PSTAR). While there are other avenues for NASA funded fieldwork (e.g., Solar System Exploration Virtual Institutes, Exobiology, and instrument proposals) the most nimble and recurring calls for funding fieldwork are these two ROSES solicitations. SSW explicitly calls for “field studies of terrestrial analogs of planetary environments” while PSTAR “solicits proposals for investigations focused on exploring the relevant environments on Earth in order to develop a sound technical and scientific basis to conduct planetary research on other

2 solar system bodies”. Both programs continue the NASA legacy of funding analog fieldwork. However, on average, the two programs together select 10 proposals each year containing analog field-based science (Table 1). In addition, NASA announced on July 6th 2020 that PSTAR will only be solicited biannually, further reducing support for field science. The raw number of selected proposals is quite small, thereby limiting the variety of field-based studies that can be achieved. Furthermore, there are important field studies that require observations to be collected on short notice or over many years (particularly of active processes) that do not fit the ROSES timelines. The limited number of field-science funding opportunities places unique pressure on filed-science proposers to submit to every call which in turn reduces the number of available reviewers with relevant and current experience. Analog fieldwork in the next decade will build on a rich history of NASA funded research. With sufficient support and dedication, field science can close critical knowledge gaps in a range of Planetary Science disciplines.

3. Science Gaps and Goals for the 2023–2032 decade

Earth Science fieldwork is conducted for many reasons on Earth including economic exploration, geohazards, environmental, and fundamental research. In support of planetary science, analog fieldwork generally falls under three broad categories: (a) to improvise scientific knowledge related to physical and biological processes; (b) to better understand the analog environment and its habitability; and (c) to better understand data and how spacecrafts or astronauts will make surface or orbital observations at other planets. Each has unique (but sometimes overlapping) implications for where fieldwork is done, what data are collected, and how existing gaps in our understanding (Table 2) will be addressed in the next decade.

a) Understand the process Geological processes have been at work on all terrestrial bodies since the time of their formation. In many cases, field studies show that remote sensing-based interpretations are mistaken about the physical processes that govern the formation of geologic features. Studying landforms on Earth that are diagnostic of physical processes can teach us to recognize subtle differences that can guide instrument development, observation strategies and experiment design. Terrestrial analog field studies provide the ground-truth for studying geological processes and bridges the gap between direct sample observations and remote sensing interpretations, key to understanding unique aspects of geologic processes beyond Earth. Analog studies of both recent and active terrestrial processes provide critical constraints for formulating, testing, and validating numerical and analytical models that are applied to planetary landforms.

b) Understand the environment Before habitability interpretations of planetary environments can be made, we first must understand how biological activity interacts with the Earth’s environment. In terrestrial settings, biology plays a key role in shaping the environment in ways that are not always observable in a laboratory. Field based studies provide the ground-truth for controlled laboratory studies as well as computational modeling and known points for model interpretation. Through understanding interactions within our own environment, and the implications they have, we can better understand alien environments and be better equipped to search them for life.

3 c) Understand the data Innovations in spacecraft instrumentation (surface and orbital) and technology present new opportunities for increasingly quantitative measurements and descriptions of surface features and deposits. Terrestrial analog fieldwork is needed to complement these new observations. High- resolution data acquired from orbit can provide broad spatial coverage, but cannot yet reveal all the details of surface features that are necessary to answer geologic questions. A key step in interpreting what will be observed on other bodies in the solar system is conducting ground-truth expeditions on Earth using similar scale (e.g., in space, duration, etc.) and similar measurement types and parameters (e.g., spectral wavelengths, etc.) to better interpret spacecraft data. Such ground-truth exercises include field-testing flight hardware in geologically well-studied regions or in-situ observations that validate remote sensing data to reconcile ground and remote perspectives. Each new mission and observation would benefit from a coupling with parallel field studies to make planetary interpretations more robust.

Table 2: Key planetary science questions and analog field studies to address them

Broad Key Question Analog Field Study Category

How have the chemical and physical Study analog geologic / geochemical processes in the U

n processes that shaped the solar system field and document landform degradation and d

e operated, interacted, and evolved over time? alteration r s t a n What locations provide real-time Comparative studies of environments permeated by d

t biogeochemical processes and biosignatures life and barren environments. h e

that are relevant to other planetary bodies? P r o c

e What can observable active surface Study analog active processes on Earth and links to s s processes tell us about the hidden deep planetary properties. subsurface?

What environmental limits are there on the Seek out habitat boundaries in extreme (acidic, propagation of life? saline, temperature, arid) environments as analogs. U

n What process intersections are beneficial for Explore intersection environments (e.g., glacio- d

e fostering habitable environments? volcanic) as analogs. r s t a n How does terrestrial biology shape the Study biologic interaction with sedimentation, d

t

h geologic landscape & how does this affect weathering, and element cycling. e

our interpretation of planetary data? E n v i

r What locations preserve ancient ecosystems Studies to characterize biochemical and o

n in the rock record that are relevant to morphological signatures of ancient rock formations m

e possible biosignatures on other planetary and deposits representative of different environments n

t bodies? at multiple scales, (e.g., easily observed by the naked eye or probed by portable instruments in the field vs micro-scale laboratory measurements of returned samples).

4 What geo-hazards would a landed crew on Quantify slope, roughness and feature specific the Moon expect? hazards at analog sites.

What are the key remote Ground-truth terrestrial remote sensing data (orbital, sensing observables, and their resolution, aerial and UAS) with field studies at “type” localities required to differentiate the products of for relevant geologic and biologic processes. physical and biological processes?

What are the requirements that must be Systematic field tests of available instruments at

U levied on landed instrument X to detect Y? “type” localities for relevant geologic and biologic n

d processes. e r s t a What sampling protocols and documentation Evaluate scientific return of samples with different n

d would a landed crew or rover need to levels of documentation taken during analog surface

t h employ to ensure science fidelity of sample activities. e

D interpretation? a t a How can we interpret geophysical Campaign geophysical observations on Earth with observations of terrestrial bodies? analogous crustal properties (e.g., ice, lava, pyroclastics, river-gravel, sand). Can we use geophysical methods (e.g., seismic, magnetometry, gravity, radar) to find and quantify subsurface voids and volatiles?

4. Solutions to Increase Science Return for NASA Fieldwork Field-based science can be difficult to propose, evaluate, and perform, and the resulting data are hard to archive because the data can be large and of varied types (e.g., photographs, LiDAR scans, notes, GPS points, radargrams, seismograms, spectra, samples, etc.) and necessitate metadata to properly use them. But the work is necessary and the data are important to the community. We present here solutions to some of the challenges that field-based studies face, in hopes that these solutions will encourage community involvement in field science, make expeditions safer, and the data more accessible.

a) Evaluating Field Sites Identifying location in the field is a difficult task and one that is given uneven scrutiny in the review process. Some locations on Earth are truly unique and provide unparalleled insight into geologic processes. Some locations might be easy to get to and can provide ready access to a multitude of science targets, while others might be too difficult to access to justify the cost and complexity. The community needs a clear structure by which proposed field sites can be evaluated and from which proposers, and reviewers, can benefit. Such a framework could be developed with community input and would aid in the proposal and review process. We suggest the community consider including: science potential, uniqueness, impact, heritage, remoteness, cost, complexity, travel requirements, and safety among other topics in a rubric for evaluating field site proposals. Such structure could help reviewers appreciate the value of a proposed project even if they are not a field expert themselves.

b) Safety in the Field

5 Safety in the field should be the first priority of the field team and expedition management alike. An effective way to foster a safe fieldwork environment is to develop a robust field safety plan. Articulating a clear safety plan allows all members of the expedition to understand what is expected of them and provides them with confidence that their safety is being considered with every decision. A field safety plan needs to be unique to the particular field-site, but can have many common attributes, including: clear leadership structure, a code of conduct, an anti- harassment policy including a reporting system and consequences for violations, and plans for fieldwork safety, illness or injury response, search and rescue, vehicle safety, and emergency numbers. While safety plans could also provide legal cover for management, it is essential to foster a culture of safety in the field. Leaders must set an example of being prepared and consistently demonstrate using sound judgement in evaluating the risks and rewards of field activities. All team members must feel empowered to raise safety and harassment concerns. This is again best accomplished by leaders taking the time to listen and thoughtfully communicate how they are including those concerns in their decision making.

c) Field Data Dissemination, Archiving and Accessibility Field data collected by NASA funded work should be archived for the community. Currently this is done individually at universities and through publications. The community needs a central location where all of the data relevant to each planet, environment and process can be searched and downloaded with ease. Archiving field data will make the fieldwork effort go farther, reduce redundancy and provide a community service by making the data accessible to all regardless of resources, ability, aptitude, or infrastructure. As one of the most rapidly developing modern technologies, Virtual Reality (VR) offers a powerful method for visualizing and interacting with data and environments that are inherently 3-dimensional in a manner not possible with traditional 2-dimensional methods and, in many ways, more accessible. VR environments can be built from existing field data or from purpose collected data sets. Meeting the need for data accessibility could be extremely costly to meet without leveraging existing capabilities being developed for terrestrial studies. The added benefit of leveraging systems developed for Earth studies is to improve communication with the broader community of scientists whose work is limited to just the Earth.

5. Actionable Recommendations The next decade will result in new science and improved understanding of geologic processes across the solar system. To ensure new conclusions are grounded in fundamentals, we recommend the following:

1. Commit to supporting planetary analog field science by funding it at a level that allows high priority field studies to be conducted across the incredibly wide array of problems of interest to NASA Planetary Science Directorate. In our view, this can be achieved by either starting a new program to specifically fund fundamental field-based studies, or by devoting a larger percentage of the Solar System Working budget to field studies (currently 3% to 11%) and returning to funding PSTAR annually. Table 2 provides a list of science questions that can be addressed in the next decade with sustained commitment. 2. Adopt a rubric for evaluating planetary analog field sites and use it in all programs that solicit fieldwork. This will give proposers a framework to evaluate their own sites before submission and reviewers’ guidelines for evaluating their proposals. 6 3. Develop, with community input, field safety plan standards for all NASA funded fieldwork. A safety plan needs to be adapted for each field site and for local conditions, but a NASA led effort to define standards can be the baseline. 4. Establish a central long-term archive for planetary analog field data (such as a Planetary Data System Node) and make archiving NASA funded field data compulsory. A central archive would improve accessibility, reduce redundancy and ensure long-term preservation. 5. Continue to support the development of data processing, visualization and analytics tools and capabilities standards, technologies and expertise (including VR) to ensure NASA funded field data are properly processed, easily discoverable and accessible for effective use to the fullest extent in support of current and future planetary science, exploration as well as strategic communication.

6. References Bulat, S.A., Alekhina, I.A., Marie, D., Martins, J., Petit, J.R., 2011. Searching for life in extreme environments relevant to Jovian’s Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica). Adv. Sp. Res. 48, 697–701. doi.org/10.1016/J.ASR.2010.11.024 Carr, M.H., Greeley, R., 1980. Volcanic features of Hawaii--a basis for comparison with Mars. Chapman, M.G., 2007. The Geology of Mars: evidence from Earth-based analogs. Cambridge University Press, Cambridge, UK. https://doi.org/10.5860/choice.45-2580 Chapman, M.G., 1997. Gene Shoemaker - Founder of Astrogeology. URL https://astrogeology.usgs.gov/rpif/Gene-Shoemaker (accessed 6.25.20). Garry, W.B., Bleacher, J.E., 2011. Analogs for Planetary Exploration. Geological Society of America. https://doi.org/10.1130/SPE483 Greeley, R., 1971. Lava tubes and channels in the lunar Marius Hills. Moon 3, 289–314. https://doi.org/10.1007/BF00561842 Greeley, R., King, J.S., 1977. Volcanism of the Eastern Snake River Plain, Idaho: A comparative planetary geology-guidebook 308. Levy, D., 2002. Shoemaker by Levy-The Man Who Made an Impact. Princeton University Press., Princeton, NJ. McKay, C.P., Friedmann, E.I., Gómez-Silva, B., Cáceres-Villanueva, L., Andersen, D.T., Landheim, R., 2003. Temperature and Moisture Conditions for Life in the Extreme Arid Region of the Atacama Desert: Four Years of Observations Including the El Niño of 1997– 1998. Astrobiology 3, 393–406. https://doi.org/10.1089/153110703769016460 Mouginis-Mark, P.J., Harris, A.J.L., Rowland, S.K., 2009. Terrestrial analogs to the calderas of the Tharsis volcanoes on Mars, in: The Geology of Mars. pp. 71–94. https://doi.org/10.1017/cbo9780511536014.004 NASA Research and Education Support Services, 2020. NSPIRES - Solicitations Summary. https://nspires.nasaprs.com/external/solicitations/summary!init.do? solId=BA231B0B067C9D42D770848B361FC4CA&stack=redirect (accessed 7.13.20). National_Research_Council, 2011. Vision and Voyages for Planetary Science in the Decade 2013-2022. National Academies Press, Washington, DC. Pavri, B., Head, J.W., Klose, K.B., Wilson, L., 1992. Steep-sided domes on Venus: Characteristics, geologic setting, and eruption conditions from Magellan data. J. Geophys. Res. 97, 13445. https://doi.org/10.1029/92JE01162

7 Stofan, E.R., Anderson, S.W., Crown, D.A., Plaut, J.J., 2000. Emplacement and composition of steep-sided domes on Venus. J. Geophys. Res. 105, 26757–26771. https://doi.org/10.1029/1999je001206

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