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Outer : Many Worlds to Explore

Outer Planets Assessment Group

(OPAG) View of Decadal

Survey Progress

May 2017 Alfred McEwen, OPAG Chair LPL, This presentation will address (relevant to OPAG): • 1. Most important new discoveries 2011-2017 – (V&V writing was completed in late 2010) • 2. Progress made in implementing Decadal advice – Flight investigations • Flagship Missions • New Frontiers – R&A and infrastructure – Technology • 3. Other issues relevant to the committee’s statement of task – Smallsats for Outer Planet Exploration – How to make the useful for Outer Planets – – Coordination with ESA JUICE mission – Adding Ocean Worlds to New Frontiers 4 – Future mission studies to prepare for next Decadal • 4. Summary grade recommendations on Decadal progress • 5. OPAG top recommendations to mid-term review

1. Most Important New Discoveries 2011-present • system: – Europa plate tectonics (Prockter et al., 2014) – Europa cryovolcanism (Quick et al., 2017; Prockter et al., 2017) – Europa plumes (Roth et al., 2014; Sparks et al., 2017) – Confirmation of subsurface ocean in (Saur et al., 2015) – Evidence for extensive melt in ’s mantle (Khurana et al., 2011; Tyler et al., 2015) – Fabulous results from (papers submitted) • System: – MUCH from Cassini—see upcoming slides • Uranus and Neptune systems: – Standard interior models do not fit observations; Uranus and Neptune may be quite different (Nettelmann et al. 2013) – Intense auroras seen at Uranus (Lamy et al., 2012, 2017) – Weather on Uranus and Neptune confined to a “thin” layer (<1,000 km) (Kaspi et al. 2013) – Ice Giant growing around nearby TW Hydra (Rapson et al., 2015) – Triton’s tidal heating and possible subsurface ocean (Gaeman et al., 2012; Nimmo and Spencer, 2015) • Pluto system—lots of results from – The Pluto system is complex in the variety of its landscapes, activity, and range of surface ages. (Stern et al., 2015; Weaver et al., 2016; Moore et al., 2016; Grundy et al., 2016; Gladstone et al., 2016; McKinnon et al., 2016) • Planet 9 (or X) predicted to exist (Trujillo and Sheppard, 2014; Batygin and Brown, 2016) 1. Most Important New Discoveries 2011-present (Continued) • Giant Planets Comparative Atmospheric Sciences – Intriguing similarities and differences in the polar atmospheric dynamics (Sromovsky et al. 2012, review by Sayanagi et al. 2016/in press) • Theory: Atmospheric Dynamics – Explanation of Saturn’s Hexagon (Morales-Juberias et al. 2011, 2015) – Explanation of Giant Planet Polar Vortices (O’Neil et al. 2015, 2016) – Moist convection’s effect on energy balance (Li and Ingersoll, 2015) – These theories explain observed phenomena • Theory: Interior Structure – Relationship between Interior Structure and Rotation Rate (Helled and Guillot 2013) – Atmospheric Jet Stability may predict interior rotation rate (Read et al. 2009) – These theories have implications for the moment of intertia of giant planets measurable through gravity. • Theory: Outer Solar System Evolution – Nice Model (Levison et al. 2011, Bottke et al. 2012…) – Grand Tack Model (Walsh et al. 2011, 2012…) – These theories have implications for the bulk composition and isotopic ratios of giant planets Cassini Accomplishments • 1. Post-2011 Enceladus:

– CDA finds salty water: H2O, Na and K salts discovered in plume particles (Postberg et al., 2011) – Internal heat source: warm south polar tectonic fractures ("Tiger Stripes” ) (Spencer et al., 2006; Howett et al., 2011; Goguen et al., 2013; Spencer et al., 2013) – Plume activity correlated with tidal stresses (Hedman et al., 2013) – RSS gravity data show that Enceladus interior is differentiated (Iess et al., 2014) – RSS gravity and ISS libration show a global liquid water ocean (Iess et al., 2014; McKinnon et al., 2015, Thomas et al., 2015) – ISS images show >100 jets and/or curtains erupt from tiger stripes (Porco et al., 2014; Spitale et al., 2015)

– CDA finds SiO2 nanograins condense from core-heated H2O (Hsu et al., 2015) – CDA and INMS find CH4 in plume from warm-water chemistry at rock-core interface (Bouquet et al., 2015) – INMS finds H2 in plume: food for life (Waite et al, 2017) • 2. : Cassini and showed us one of the most -like worlds we’ve ever encountered, with weather, climate and geology that provide new ways to understand our home planet; see later slide • 3. Rings: Cassini showed us the complexity of Saturn’s rings and the dramatic processes operating within them. • 4. Icy Moons: Cassini revealed Saturn’s moons to be unique worlds with their own stories to tell. • 5. Saturn and Titan: The length of Cassini’s mission has enabled us to observe weather and seasonal changes, improving our understanding of similar processes at Earth, and potentially those at planets around other stars. See https://saturn.jpl.nasa.gov/mission/top-tens/images/ for top-10 Cassini results for each year.

Seafloor Dust Captured by Cassini

Silica nanoparticles captured by Cassini provides first evidence for ongoing seafloor hydrothermal activity.

Hydrothermal activity occurs when seawater infiltrates and reacts with a rocky core, emerging as a heated, mineral- Earth laden liquid. Titan Discoveries

Year paper Summary of Discovery Accepted (V&V priorities were finalized Sept 2010) 2010 Changing shoreline of northern seas 2011 Titan south polar vortex 2011 rain storm 2012 Global subsurface ocean 2012 Seasonal change in atmosphere circulation 2012 Tropical lakes 2013 Definitive detection of a plastic ingredient 2013 Confirmation of complex in Titan's upper atmosphere 2013 Large Abundances of Polycyclic Aromatic Hydrocarbons in Titan's Upper Atmosphere 2013 Titan’s ionospheric density linked to solar activity 2014 First determination of depth of a Titanian sea 2014 Titan's "Magic Islands": initial discovery 2014 Titan's ocean as salty as Dead Sea 2014 Methane Ice Cloud in Titan’s Stratosphere 2014 Titan Observed Outside of Saturnian Magnetosphere 2015 Titan dissolves to form small lake basins 2016 "Magic Islands" ongoing observations Seasonal Rains Transform Titan's Surface (Turtle et al., 2011) Cassini Mission

56 Flybys

12 Flybys Cassini Makes Historic Passage

On April 26, 2017, Cassini made the first historic passage between Saturn and its rings marking the beginning of Cassini’s Grand Finale.

Unique science goals during the Grand Finale include studying Saturn’s interior structure, measuring the mass and composition of the rings, and analyzing composition of uppermost atmosphere. Read more about it here: https://go.nasa.gov/2poRfE1 2. Progress made in implementing Decadal advice • A. Flight investigations – Flagships – New Frontiers – Discovery (none) discussed later • B. R&A and infrastructure (Earth-based observing, DSN, Pu-238) • C. Technology A. Outer Planet Mission recommendations in V&V • The recommended program: – • Discovery program funded at the current level adjusted for inflation, • How are we doing so – • Mars conducted jointly with ESA, far? – • New Frontiers Missions 4 (includes Saturn • Descoped JEO Europa probes) and 5 (adds Io Observer) Clipper: NASA deserves – • MAX-C (descoped to $2.5 billion), an “A” • Uranus Orbiter and probe: – • Jupiter (descoped), and unlikely to get a new start – • Uranus Orbiter and Probe. this decade, “D” • The cost-constrained program: • New Frontiers 4 underway – • Discovery program funded at the current level but 5 may not make this adjusted for inflation, decade: I (incomplete) – • Mars Trace Gas Orbiter conducted jointly with • Bonus points for adding ESA, Enceladus and Titan – • New Frontiers Mission 4 and 5, • Improved budget picture – • MAX-C (descoped to $2.5 billion), and should lead to NF-6 this – • Uranus Orbiter and Probe. decade • Discovery: I (incomplete) • Improved budget picture: – 1. An increase in funding for the Discovery program, – 2. Another New Frontiers mission, and – 3. Either the Enceladus Orbiter mission or the Venus Climate Mission.

OPAG Extended Missions: Cassini • From V&V: ”Continue missions currently in flight, subject to approval obtained through the appropriate senior review process. These missions include the Cassini mission to the Saturn system, ... Ensure a level of funding that is adequate for successful operation, analysis of data, and publication of the results of these missions, and for extended missions that afford rich new science return. • NASA has followed this advice OPAG Flagship missions 1. • This mission satisfies V&V recommendation for descoped JEO • Entering Phase B; 9 science instruments accommodated • OPAG strongly supports this mission.

Pop Quiz

What major (known) planets in our Solar System have never had a dedicated spacecraft mission? Uranus and Neptune The Ice Giants: An unexplored class of planet

HST image of Neptune and Triton Uranus: It isn’t always bland OPAG Flagship Missions: 2. Uranus Orbiter and Probes • V&V quotes: – The third-highest-priority flagship mission is the Uranus Orbiter and Probe mission. – …many exoplanets are ice-giant size. – Exploration of the ice giants Uranus and Neptune is therefore the obvious and important next step in the exploration of the giant planets. – ... a Uranus mission is favored for the decade 2013-2022 for practical reasons (no Jupiter gravity assist; cruise time to Neptune exceeded ASRG lifetime) – Many unknowns remain as to how the outer planets formed out of the solar nebula and if and when they migrated into different orbits. • ... testable predictions for noble gas abundances in the other giant planets—definitive answers will require in situ probe measurements—critical data that researchers lack for Saturn, Uranus, and Neptune. – Uranus and Neptune have tilted magnetospheres offset from their centers, configurations that could provide new insights into ice-giant exoplanets. • Icy moons Triton and Ariel might be ocean worlds – Tilted magnetospheres enable probing for conductive interiors

• NASA does not seem to have any intention of starting this mission before 2023. • See Ice Giants SDT presentation, for the next decade.

OPAG Flagship Missions: 3. Enceladus Orbiter

• Recommended in V&V augmented funding scenario • Science Objectives: – Investigate the internal structure, geology, and chemistry of Enceladus and plumes discovered by Cassini – Prepare for potential future landing – Observe interactions between Enceladus and the Saturn system and explore the surfaces and interiors of Saturn’s Moons – Key science issues addressed: • Investigating the nature of Enceladus’s cryovolcanic activity • Providing improved measurements of plume gas and dust • Measuring tidal flexing, magnetic induction, static gravity, topography, and heat flow • Cassini extended mission already accomplished many of these objectives • OPAG steering committee thinks that an emphasis on habitability, prebiotic chemistry, and search for life is more appropriate for future Enceladus missions • Key Question: Is robust life detection possible via New Frontiers, or is a larger mission needed? – Wait for reviews of NF-4 Enceladus proposals New Frontiers Missions to Outer Planets

• Missions from the 1st Decadal survey: – New Horizons • (SBAG and OPAG have joint custody of Pluto) – Juno • Approved candidate missions in V&V: – Saturn Probe (NF-4+5) – Io Observer (to be added in NF-5 if AO released before 2023) – Enceladus and Titan Ocean worlds • recent addition to NF-4 (to be discussed later) • More New Frontiers missions to Outer Planets and Ocean Worlds is a top OPAG priority. – Discovery hasn’t worked out and Flagship missions are infrequent – Note V&V decision rules for an augmented budget scenario includes another New Frontiers mission before a new Flagship mission. Saturn Probe

Science Objectives (from V&V): • Determine noble gas abundances and isotopic ratios of hydrogen, carbon, nitrogen, and in Saturn’s atmosphere • Determine the atmospheric structure at the probe descent location • Key science issues addressed: – Constraining models of solar system formation and the origin and evolution of atmospheres – Providing a basis for comparative studies of the gas and ice giants – Providing a link to extrasolar planetary systems Io Observer Science Objectives • Study Io’s active volcanic processes; • Determine the melt fraction of Io’s mantle; • Constrain tidal heating mechanisms; • Study tectonic processes; • Investigate interrelated volcanic, atmospheric, plasma-torus, and magnetospheric mass- and energy- exchange processes; • Constrain the state of Io’s core via improved constraints on whether Io generates a magnetic field; and • Investigate endogenic and exogenic processes controlling surface composition. Deep interior (left) vs lithosphere dissipation (right) tidal heating models (Ross et al.,1990) can be Tidal heating driving Io’s activity tested by Io Observer. controls the Jovian system’s habitable zone and understanding it gives into potential habitats in extrasolar planetary systems. Potential existence of active ultramafic volcanism has implications for early volcanism on Earth and terrestrial planets. Voluminous volcanism leading to mass extinctions can only be directly observed on Io. B. Research & Analysis

Quotes from V&V: • The committee recommends that NASA increase the research and analysis budget for by 5 percent above the total finally approved FY2011 expenditures in the first year of the coming decade, and increase the budget by 1.5 percent above the inflation level for each successive year of the decade. • The committee strongly encourages NASA to find ways (e.g., by merging related research programs and lengthening award periods) to increase average grant sizes and reduce the number of proposals that must be written, submitted, and reviewed by the community. – This hasn’t happened? NASA R&A reorganization: • Was the source of much confusion within the science community, and suspicions about its motivation. • Selection rates decreasing • Not clear how Outer Planets research is doing after re-org, given fluctuations – OPAG urges continuation of CDAP well after the end of the Cassini mission B. Infrastructure • Earth-based observing – V&V states in multiple places how valuable HST is for solar system studies, and that it’s unique in its UV capabilities, and that no follow- on is planned. – "The committee recommends that future Discovery AOs allow space- based telescopes to be proposed, and that planetary science from space-based telescopes be listed as one of the goals of the Discovery program.” • There is no such wording in the 2014 Discovery AO – OPAG is concerned about the impending loss of the unique capabilities of HST and urges NASA to support space-based telescopes • Discovery, or Large Ultraviolet-Optical-Infrared Surveyor (LUVOIR) • Pu-238/RPS – OPAG notes the significant progress being made in the area of RPS. OPAG urges PSD to rapidly advance RPS systems to enable the end-of- mission power levels required for outer planet science missions. • Deep Space Network (DSN) – It is imperative that current DSN capabilities be maintained

C. Technology (progress made in implementing V&V) V&V Classification by Technology Element—all relevant to OPAG

24 OPAG Technologies • NASA PSD has done a reasonable job in trying to meet the Decadal Survey recommendations, especially in light of the budget downturn earlier in this decade. – Instrument Concepts for Europa Exploration (ICEE), Homesteader, and ColdTech proposal calls issued for instruments, in addition to PICASSO ands MatISSE – Planetary Science and Technology through Analog Research (PSTAR)-- ocus on identification of life • Tech development for power is a high priority to OPAG – in V&V, the highest priority for multi-mission technology investment was the Advanced Sterling Radioisotope Generator (ASRG). • There is now some urgency to technologies for Ocean Worlds – Technology investment is needed as soon as possible for the potential Europa Lander and potential competed missions, including new life detection instrumentation. – Expert reviewers with a better understanding of novel life instruments and extreme environment technologies may have to be sought from a broader swath of the community (including those with biological expertise). • Continue developing the technologies needed for Ice Giant mission - eMMRTG and HEEET • A pathway to infusing technologies in future missions and a plan for their management are needed so that PSD develops these technologies with a view to using them. 3. Other Issues relevant to the committee’s statement of task • A. Smallsats for Outer Planet Exploration • B. How to make the Discovery Program useful for Outer Planets • C. Europa Lander • D. Coordination with JUICE • E. Adding Ocean Worlds to New Frontiers 4 • F. Future mission studies to prepare for next Decadal

A. Are Smallsats useful for Outer Planets? • Cubesats are great in low-Earth orbit because: • Released directly into orbit—no large propulsion system needed • Close to Earth—no large telecom system needed • Within Earth’s magnetosphere—little radiation design needed • Close to Sun—no power challenge • Mission can start immediately—long life does not need to be demonstrated • None of these advantages apply to the outer Solar System! • Only possibility is a smallsat that rides along with large mission • Concepts considered and rejected for Europa Clipper • Enceladus-like water plumes on Europa would be only ~20 km high, so a smallsat could be released to fly through the plume for in-situ analyses • Smallsats must not endanger the expensive mission • Selections for Planetary Science Deep Space SmallSat Studies (PSDS3): • Small Next-generation Atmospheric Probe (SNAP) • Atmospheric entry probe to measure vertical cloud structure, stratification, and winds to help understand the chemical and physical processes that shape the atmosphere of Uranus. • JUpiter MagnetosPheric boundary ExploreR (JUMPER) • SmallSat to explore Jupiter’s magnetosphere, including characterizing the solar wind upstream of the magnetosphere to provide science context for future missions such as the Europa Clipper. • Conclusion: Smallsats may be useful in special cases, but this is not a new paradigm for exploration of the outer Solar System

B. The problem with Discovery for OPAG

Congressional Direction:

From the Commerce, Justice, Science, and Related Agencies Appropriations Bill, 2016:

“...The Committee directs NASA to create an Exploration Program whose primary goal is to discover extant life on another world using a mix of Discovery, New Frontiers and flagship class missions consistent with the recommendations of current and future Planetary Decadal surveys.” Outer Planet Missions in Discovery? • will go to 5 AU but does not visit a planetary system • Missions proposed but declined: – INSIDE Jupiter (evolved into Juno in New Frontiers) – (TiME) (made it to step-2; ASRGs) – Journey to Enceladus and Titan (JET) – (ELF) – Life Investigation for Enceladus (LIFE) – (IVO) – Kuiper (UV to NIR telescope) • Outer Planets exploration is challenging via Discovery – Mission/instrument lifetime requirements • Discovery 13 change putting Phase E outside cost cap has helped, but still need to demonstrate lifetime of S/C and instruments – High radiation environment at Jupiter – Cold environments (plus hot during Earth/Venus gravity assists) – Challenging for power at >5 AU • Very large LILT solar arrays or radioisotope power – Need large propulsion system to be captured into orbit – Need large telecom system to return significant amounts of data • Either NASA needs to change the AO rules or Discovery will not help OPAG or Ocean Worlds (e.g., congressional language) – RTGs as GFE without cost cap penalty? – Raise Discovery cost cap for challenging missions? – Accept higher risk? • Fly an extra New Frontiers mission in place of 2 Discovery missions?

C. Europa Lander

• Separate from Clipper. • Target launch: 2024-2025. • Battery powered mission: 20+ day surface lifetime. • 42.5 kg allocation for science payload. • Baseline science includes: – Analyses of 5 samples, – Samples acquired from 10 cm depth or deeper (beneath intensely radiation processed regolith) – Each sample must have a minimum volume of 7 cubic centimeters. Europa Lander Goals & Objectives Addressed with a Focused Model Payload

GC-MS Microscope Raman spectrometer Context cameras

Raman Raman spectrometer spectrometer Microscope

GC-MS GC-MS

Context Context cameras cameras

Geophone Geophone

Pre-Decisional Information — For Planning and Discussion Purposes Only What does V&V say relevant to a Europa Lander?

V&V has extensive comments about the search for life: • “The primary goals of NASA’s PSD are to ascertain the origin and evolution of the solar system and to understand the potential for life beyond Earth. “ • Priority question #6: “Beyond Earth, are there contemporary habitats elsewhere in the solar system with necessary conditions, organic matter, water, energy, and nutrients to sustain life, and do organisms live there now? Important objects for study: Enceladus, Europa, Mars, and Titan. “ • “Satellites provide many of the most promising environments for the evolution of , or for understanding the processes that led to the evolution of life on our own planet.” • “Important objectives relevant to this goal include ... Is there evidence for life on the satellites?” • “The search for evidence of life is an emerging science priority for the moons of the outer solar system. Studies of the plume of Enceladus and any organics on the surface of Europa (or in potential Europa plumes) may provide evidence of biological complexity even if the organisms themselves are no longer present or viable.”

Only one specific reference to a Europa Lander: • “A key future investigation of the possibility of life on the outer planet satellites is to analyze organics from the interior of Europa. Such analysis requires either a lander in the far term or the discovery of active Enceladus-style venting, which would allow analysis from orbit with a mission started in the next decade.” A Science Strategy for the Exploration of Europa, National Academies (Greeley et al., 1999)

“COMPLEX concludes that Europa should have a priority for future investigation equal to that accorded to Mars.” “…the report underlines the need for a systematic approach to obtaining a global view of Europa science, rather than attempting a rapid and possibly poorly conceived rush to detect life.”

Summary of prioritized mission recommendations 1. Comprehensive Europa science mission (satisfied by Europa Clipper) 2. Lander to understand in situ determination of the composition of the ice and of any non-ice surface components, including the bulk material, trace elements, isotopes, and mineralogy; analyses of any organic molecules at or near the surface, and identification of endogenic or exogenic sources; determination of the composition and properties of the atmosphere and of any materials sputtered from the surface; and estimation of the absolute ages of surface materials. 3. Access water to search for life (they did not advocate searching for life on Europa’s surface)

Findings of the Outer Planets Assessment Group (OPAG) from the meeting in Atlanta on February 22, 2017 1. Europa Lander • OPAG thanks the Europa Lander Science Definition Team (SDT) for their report and presentation to OPAG. • …exciting to think about examining Europa's habitability and searching for biomarkers, and • we support careful review of the Europa Lander concept and its scientific objectives as part of the Decadal mid-term review and, potentially, the next Decadal Survey. • Part of that review should be assessment of the value of that mission should it not discover life. • We support the SDT recommendations for early work on technologies needed to achieve the Europa Lander's ambitious science and goals. • OPAG notes that the Europa Clipper is critical as a precursor, • for identifying a landing site that is both hazard-free and provides access to very recent deposits from the ocean, and • providing the basic understanding of Europa needed to place lander results in context. • The upcoming town halls (at LPSC and AbSciCon) will help to gather useful community feedback on the mission. • We would also like to reiterate the importance of the Decadal Survey recommendation that any Europa mission should happen "without eliminating any other recommended missions.”

Finding 1: OPAG encourages careful vetting of the Europa Lander mission and how and when to implement this in a way that satisfies the Decadal Survey. D. Coordination with JUICE

• The Jupiter Icy Moons Explorer (JUICE) is the first large-class mission in ESA's Cosmic Vision 2015-2025 programme. Planned for launch in 2022 and arrival at Jupiter in 2030, it will spend at least three years making detailed observations of the giant gaseous planet Jupiter and three of its largest moons, Ganymede, and Europa.

• NASA provided funding for UVS and partial funding for PIMS and RIME.

• There are U.S. Co-Is on other teams who have no funding

• Coordination with Europa Clipper has not been happening so far • Synergistic science, especially comparison of Europa and Ganymede E. Adding Ocean Worlds to New Frontiers 4

• OPAG strongly supports including Titan and Enceladus in New Frontiers • Clearly fits top NASA and V&V priorities: Habitability, search for life, prebiotic chemistry • They were excluded from NF in V&V due to technicalities: • Titan and Enceladus already had Flagship mission studies • Insufficient time to develop NF mission concepts • Tight limit on number of full studies supported for V&V • Many new Cassini discoveries since V&V • The controversy seems to be whether it was appropriate to add them to the NF-4 AO • Congressional language said to include Ocean Worlds in NF and Discovery • Discovery challenging for Ocean Worlds • If not included in NF-4, there could be at least a 5 year delay, not very responsive to congress. • Are Ocean Worlds concepts sufficiently mature for NF-4? • At least four teams think so • Step-1 proposals submitted last week • If not selected for NF-4, they will be more mature for NF-5+

F. Future Mission Studies for Next Decadal

• New mission studies across the Solar System are needed to inform the next Decadal Survey. • Missions to Jupiter and icy Galilean satellites are underway – Wait for results to plan next steps? • Europa Lander SDT completed, more studies? • Missions to Saturn are part of NF-4 competition – Wait until selection to start new studies • Ice Giant Mission SDT study is near completion. • Next space telescope studies underway in Astrophysics • Far-Infrared Surveyor, X-Ray Surveyor, Habitable-Exoplanet Imaging Mission (HabEx), and Large Ultraviolet-Optical-Infrared Surveyor (LUVOIR) • What’s left to study? – Io Observer (next slide) – Future Ocean Worlds mission concepts (later slide) – Missions to Large KBOs • (OPAG-SBAG joint custody of planet-like worlds) • Could include flyby of giant planet Io Mission Study for next Decadal Survey • An Io Observer was listed by New Frontiers in the Solar System, the 2003 Decadal Survey, as a Deferred high-priority mission, and by Visions and Voyages as one of seven high-priority medium-class mission candidates. • Vision and Voyages recommended an Io Observer for inclusion among the candidates for the New Frontiers Mission 5. – Since the NF-4 AO was only released in late 2016, it seems unlikely that NF-5 will be solicited in the current decade. • An Io Observer, is, therefore, a top OPAG priority for including in the next Decadal Survey and a mission study is an important preliminary step. • There have been significant recent advances in technology and scientific understanding relevant to Io driven by the Europa Clipper and Juno missions. • Open this to alternate Io mission concepts? • Also of interest to heliophysics: Io Electrodynamics Mission ROW: mission studies in advance of next Decadal (these are not prioritized) • Europa missions well studied – But Mr. Culberson wants a probe in the ocean next decade—that needs more study • Ganymede & Callisto awaiting JUICE results • We are ready to take the next steps (characterizing habitability and searching for life) at the known Ocean Worlds Titan & Enceladus – Titan • orbiter • in situ element(s) - boat/submarine/landers/rovers/aircraft – Enceladus • plume sample analysis • sample return • In situ lander, crawler, or submarine • We also want to establish whether oceans are present at possible Ocean Worlds – Triton is a high priority to ROW. • Should be accomplished as part of an Ice Giants mission to Neptune • Triton is a higher priority but Ariel is an alternative for a Uranus mission 4. V&V midterm grades: The OPAG perspective

• Cassini extended mission: A • Europa Clipper: A • Uranus orbiter with probes: D • New Frontiers: I (incomplete) • Discovery: I • Technology: B • Infrastructure: I • R&A: C 5. OPAG Take-Home Messages • OPAG strongly supports more New Frontiers missions • OPAG strongly supports an Ice Giants mission • Discovery program needs modification to be useful for Outer Planets • OPAG strongly supports the Ocean Worlds concept – Europa Clipper, also a lander? – Titan and Enceladus in New Frontiers – Triton (and Ariel) in Ice Giant mission(s) – Surface/subsurface missions to ocean worlds • OPAG strongly supports other outer planet mission concepts – Saturn Probes – Io Observer • Key technologies & infrastructure must be supported – Life-detection instruments, sampling and handling technologies, autonomy, low T electronics, Pin-point landing on Titan, Cryogenic sample return – DSN, RTGs, Earth-based telescopes • R&A must be well supported – New emphasis on Ocean Worlds • New mission studies needed to prepare for next decadal