Cynthia B. Phillips

The Europa Clipper spacecraft is located about 1 au downstream from the interstellar comet 3I/ATLAS around its perihelion. Here we model the propagation of pickup ions and cometary dust originating from 3I/ATLAS to examine their detectability by the Europa Clipper spacecraft. Our results suggest that while pick up detection is possible, the dust tail will not reach the Clipper spacecraft, Mars, nor the Jovian system.

Impact craters are rare on the icy ocean world Europa: only 24 ≧ 10 km in diameter are currently observed. Craters ≳20 km in diameter, such as Pwyll and Manannán, display unusual morphologies, perhaps because they excavate down close to the subsurface ocean. Previous work suggests that Manannán may have impacted into liquid, slushy ice or thinner ice than at Pwyll. Here we show that impact craters, via their intrinsic morphologic and compositional properties, as well as impact‐excavation of otherwise unobservable materials, provide windows into subsurface structure and composition, making them natural laboratories for investigating Europa's habitability. We find that both Pwyll and Manannán excavated dark material from ∼3.1 km deep, which could be intriguing non‐ice materials such as H ₂ SO ₄ or hydrated minerals. We calculated that Pwyll impacted into a solid ice shell of ≧10.7 km thickness. We hypothesize that Manannán may have impacted into less viscous material, and detail how this can be tested with future Europa Clipper data. We also hypothesize that a reservoir of sub‐surface impact‐induced material sourced the lobate material within Pwyll. This hypothesis can also be tested with Europa Clipper data and, if confirmed, would provide targets to observe salts derived from potentially some of the most processed brines on Europa.

Impact gardening is the fundamental Solar System process by which repeated impacts mechanically churn the near surfaces of airless planetary bodies. In the absence of an Iapetus-specific analysis of gardening, the analogy of the lunar gardening rate by primary impacts was invoked in initial analysis to diminish the importance of gardening compared to sublimation for the evolution of Iapetus’ extreme albedo dichotomy [1]; however, gardening on the Moon is not like gardening on Iapetus. The Moon is rocky, is struck primarily by near-Earth asteroids, has relatively high surface gravity, and impacts by secondaries vastly outpace impacts by primaries in the uppermost meter. Thus, gardening must be unique on Iapetus, following the unique combination of its icy surface, location in orbit around Saturn, and encounters with comets, Phoebe ring, and E ring dust.We present new and unique calculations of impact gardening depth and rate specific to Iapetus. We use the generalized model, validated when parameterized for the unique lunar case [2], and deployed to investigate the distinct gardening conditions on Jupiter’s icy satellite Europa [3] and the dwarf planet Ceres [4]. Here, we tailor the gardening model to Iapetus, utilizing models of secondary crater production on Iapetus [5] and recent updates to knowledge of the impact rate at Iapetus [6]. The model demonstrates that gardening can exceed the depths eroded by sublimation, cycling fresh material below an evolved layer of thermal lag upward toward less thermally stable conditions at the surface, and contributing to the evolution of Iapetus’ extreme albedo dichotomy to an extent far greater than previously assumed. [1] Spencer, J. R., & Denk, T. (2010). Formation of Iapetus’ extreme albedo dichotomy by exogenically triggered thermal ice migration. Science, 327(5964), 432-435.[2] Costello, E. S., Ghent, R. R., & Lucey, P. G. (2021). Secondary impact burial and excavation gardening on the Moon and the depth to ice in permanent shadow. Journal of Geophysical Research: Planets, 126(9), e2021JE006933.[3] Costello, E. S., Phillips, C. B., Lucey, P. G., & Ghent, R. R. (2021). Impact gardening on Europa and repercussions for possible biosignatures. Nature Astronomy, 5(9), 951-956.[4] Costello, E. S., Ghent, R. R., & Lucey, P. G. (2021). Impact gardening on Ceres. Geophysical Research Letters, 48(8), e2021GL092960.[5] Bierhaus, E. B., McEwen, A. S., Robbins, S. J., Singer, K. N., Dones, L., Kirchoff, M. R., & Williams, J. P. (2018). Secondary craters and ejecta across the solar system: Populations and effects on impact‐crater–based chronologies. Meteoritics & Planetary Science, 53(4), 638-671.[6] Bottke, W. F., Vokrouhlický, D., Nesvorný, D., Marschall, R., Morbidelli, A., Deienno, R., ... & Levison, H. F. (2024). The bombardment history of the giant planet satellites. The Planetary Science Journal, 5(4), 88.

NASA’s Europa Clipper mission will explore Jupiter’s icy moon via multiple flybys in the early 2030s. The ocean world Europa is one of the most promising locations to search for life elsewhere in the solar system, and thus Europa Clipper’s main goal is to characterize Europa’s habitability. In the future, especially if Europa Clipper finds that Europa is habitable, a follow-on landed mission may explore Europa’s surface to search for evidence of life. Here we show that 12 of the 49 prime-mission Europa Clipper flybys are “reconable,” meaning they contain at least one portion of the ground track where the requirements for collecting data necessary for terrain relative navigation (TRN) are fulfilled. TRN would be used by a future mission to navigate to a landing site. Using data from the prior Galileo mission, we study what is currently known about these reconable areas and rank them. Three reconable flybys are ranked highest because of their particular scientific potential, which we discuss based on existing studies. We also identify and rank supporting flybys, which are not themselves reconable but provide data for additional characterization of reconable areas. These current rankings demonstrate the process for assessing reconable areas and reflect present-day knowledge. Future decisions on landing site location(s) would be based on new knowledge from Europa Clipper and would likely yield different priorities than the current rankings. We conclude that there are areas on Europa with particular scientific interest that Europa Clipper will be able to fully characterize for potential future in situ exploration.

The NASA Europa Clipper mission will explore Jupiter’s icy moon Europa via multiple flybys in the early 2030s (Pappalardo et al., 2024). The ocean world Europa is one of the most promising locations to search for life elsewhere in the Solar System and thus, Europa Clipper’s main goal is to characterize Europa’s habitability (Vance et al., 2024).In the future, a follow-on landed mission may possibly explore Europa from its surface (Phillips et al., in revision). Based on current technology, terrain relative navigation (TRN) would be used to safely navigate to a landing site. Here we show that 12 of the 49 currently designed Europa Clipper flybys contain at least one portion where the fundamental requirements for TRN are fulfilled: - daytime illumination with incidence angle ~30° to 60°; - and 0.5 to 1 meter pixel scales, which for acquisition by the EIS instrument means that the altitude is 50–100 km.We use the term ‘reconable’ to refer to these 12 flybys. Using data from the Galileo mission, we study what is currently known about these reconable areas, and rank them based on scientific criteria. Three of the reconable flybys have exceptional scientific interest, and therefore receive the highest rank 1*, where * denotes a reconable flyby. Rank 1* flybys are E5, E19 and E22. The remaining nine reconable flybys are a lower rank of 2*, where * also denotes a reconable flyby.We also identify and rank supporting flybys, which are not reconable in themselves but provide supporting data that can be used to further characterize the reconable areas. Rank 2 supporting flybys provide particularly insightful and/or necessary contextual data. Rank 3 are default supporting flybys. The current rankings reflect our present-day knowledge, and are highly likely to change with Europa Clipper’s in-depth study of the moon’s geological, geochemical and geophysical characteristics.Our work demonstrates the process that can be used by the Europa Clipper team to assess reconable areas. We conclude that there are areas on Europa with particular scientific interest that Europa Clipper will be able to fully characterize for potential future in-situ exploration.

In planetary exploration, once a landing site has been selected and a mission has successfully landed, one of the next decisions will be sampling location. Stationary missions that do not have the benefit of mobility, such as pathfinding landers to ocean worlds like Europa, and those limited by surface lifetime, will require some degree of autonomy in the selection of sampling locations within a reachable workspace (Hand et al., 2022). Therefore, the process of sample location selection is worth constraining.In this work, we investigate Apollo 16 and 17 sampling sites, treating the Moon as our best Europa analogue. We use archival reports, imagery, and other data of four Apollo 16 and three Apollo 17 sites and their corresponding drive tube core samples to constrain how the surface appearance of sampling sites couples with subsurface geology. The surface and subsurface geology are summarized using bin classifications for grain size and shape as first-order representations of regolith formation processes, and then compared with each other and contextualized by descriptions of the astronauts’ sampling decision-making to understand the impact factors in sampling the surfaces of worlds like the Moon. The work is relevant to other data-constrained, short-lived surface sampling missions that will rely on autonomy, as well as future human sampling activities during crewed exploration (e.g., the Artemis program).References Hand, K. P., C. B. Phillips, A. Murray, J. B. Garvin, E. H. Maize, R. G. Gibbs, G. Reeves, et al. 2022. “Science Goals and Mission Architecture of the Europa Lander Mission Concept.” The Planetary Science Journal 3 (1): 22. https://doi.org/10.3847/psj/ac4493.

Scheduled to launch in October 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s icy ocean world Europa. After a 5.5 yr cruise that includes gravity assists at Mars and Earth, the spacecraft will enter orbit around Jupiter and will perform nearly 50 flybys of Europa over a four-year period. To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives to characterize: (1) the ice shell and ocean including their heterogeneity, properties, and surface–ice–ocean exchange; (2) Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) Europa’s geology including surface features and localities of high science interest. Additionally, several cross-cutting science topics will be investigated through searching for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. These science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS) consisting of a wide and a narrow angle camera (WAC, NAC), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be obtained using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system.Assembly, test, and launch operations (ATLO) of the Europa Clipper spacecraft are progressing well, and the flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. Currently, the flight system is undergoing operations testing, and in May 2024, the spacecraft will be shipped to NASA’s Kennedy Space Center at Cape Canaveral, Florida. There, the remaining integration activities will occur for the solar array and REASON antennas followed by final flight system tests. The launch period begins on 10 October 2024. To provide details on the mission’s instruments and planned investigations, the Europa Clipper science team is publishing manuscripts in a special issue of Space Science Reviews, and the team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. As well, collaborative science opportunities with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter and make observations of Europa, are being discussed informally among the science teams. Onward to Europa!

In November 2023, the Europa Clipper science team held their group meeting in San Juan, Puerto Rico, chosen in part because of the existing partnership with University of Puerto Rico (UPR) and Here2Observe (H2O) program [1, 2]. Leveraging this opportunity, several moments were dedicated to interact with the broadest audience possible around bilingual events in English and Spanish (when possible). Overall, these activities required 56 volunteers and reached over 1500 people. Why include education activities in a science team meeting?The prime objective of science team meetings is to share updates on mission and science topics and encourage collaborations. However, leveraging this concentration of scientists and engineers in one location can be a great tool to build connections with local communities all over the country, especially underserved communities. NASA missions are a great vector to engage the public, inspire the next generation, and help provide a sense of ownership of these publicly funded projects to a broader audience. It is also a cost, carbon and time efficient way to connect with the community. Secondary school students: hands-on activities15 local schools traveled to the conference where they engaged with different hands-on activities modeling complex concepts in an easily-understood way led by Clipper team members. All activities were aligned with Next Generation Science Standards [4], relevant to their curriculum and easily adaptable to different age groups. Four activities were selected from JPL’s Education Office for their relevance to Europa: Solar system scroll [5]: comprehending distances in the solar system Ocean worlds density [6]: playing with the mass and density of known elements to predict Europa’s interior layers Ocean worlds magnetism [7]: exploring the relationship between magnetism and electricity to model how scientists discovered Europa’s salty ocean Mapping alien worlds [8]: build a planetary surface from simulated radar measurements using colored building blocks Such an event is scalable to the number of volunteers and type of venue available. Here, we had a high engagement of science team members which allowed us to maximize the impact to the extent the local infrastructure allowed.Fig. 1: Ocean worlds magnetism in action.Fig. 2: Mapping alien worlds in action.University students: Poster session and panel discussion Europa Clipper sponsored a poster session for 105 university students which followed the model of a professional science conference. They presented their work to Clipper team members, as well as representatives of NASA’s Science Mission Directorate’s Planetary Science Division (PSD), giving plenty of opportunities for small group discussions about science and career. The session was accompanied by a panel discussion with Lori Glaze, PSD director, Bonnie Buratti, Deputy Project Scientist on Europa Clipper, and UPR professors Abel Mendez, Raiza Quintero, Carmen Pantoja, Mayra Santos, and Desiree Cotto-Figueroa, who spoke about research opportunities for students at UPR.Fig. 3: UPR student presenting their work to scientists of the Europa Clipper mission.Fig. 4: UPR students presenting their work to Lori Glaze, director of PSD.Elementary schools: Livestream event in Spanish The reach and accessibility of in-person events is always limited. To expand beyond that, a live stream broadcast in Spanish was organized for elementary schools across Puerto Rico - 82 schools signed up. An interview-style conversation between Brandon Rodriguez, Education Specialist at JPL, and Tim Larson, Deputy Project Manager for Europa Clipper was followed by a Q&A session. Participating classrooms also received a packet of information and activities to continue the experience beyond the stream. Public: Star Party in a unique locationFinally, a public event was organized in collaboration with local Solar System Ambassadors, the science museum EcoExploratorio and Sociedad de Astronomía de Puerto Rico, at the National Historic Site Castillo San Felipe del Morro in Old San Juan. Sadly, the weather did not cooperate and we had to contend with the rain. Under a tent, the audience attended a series of presentations by Europa Clipper’s leadership and our hosts. The highlight was a reading of Ada Limon’s “Praise Of Mystery” poem in English by Roque Raquel Salas Rivera followed by their own translation in Spanish. Fig. 5: Roque Raquel Salas Rivera at star party.Lessons learnedIncluding outreach and education activities during the Europa Clipper science team meeting was very successful. It deepened the team’s relationship with Puerto Rico and demonstrated the commitment of the mission to our local partners with whom we built these events in the context of a broader and consistent relationship. Team members found these interactions both fun and meaningful, and a large majority want to continue to include significant outreach activities in future science team meetings. We also learned valuable lessons:More Spanish speakers needed: despite most students in Puerto Rico studying English in schools, we found varying levels of English fluency. The assistance of our few Spanish-speaking team members and Observers was essential and greatly appreciated. Audience knowledge shouldn’t be assumed: e.g. the solar system scroll activity assumes the audience knows the names of the planets and their order. We adjusted in real time by providing images of all the planets with their names in English and Spanish. Navigating technical difficulties: many schools were unable to log in to the live stream event, but a recording was shared with students the same day. Contingencies for outdoor events: we can’t control the weather! The presence of the science team meeting of NASA’s latest flagship mission in Puerto Rico was significant and highly covered by the local media. These events showed how much the public is...

Introduction: In October 2024, NASA’s Europa Clipper will launch on a journey to explore the habitability of Jupiter’s moon Europa. At the beginning of the next decade, the spacecraft will orbit Jupiter, flying by Europa nearly 50 times over a four-year period to: (1) Characterize the ice shell and any subsurface water, including their heterogeneity, ocean properties, and the nature of surface-ice- exchange; (2) understand the habitability of Europa’s ocean through composition and chemistry; and (3) understand the formation of surface features, including sites of recent or current activity, and characterize high science interest localities. In addition, the search for current activity cross-cuts these three principal science objectives.Flight System: The Flight System (Figure 1) comprises the Propulsion Module, which provides the thermally-controlled spacecraft structure, propulsion subsystem, and solar array (not shown); the Avionics Module, which enables spacecraft guidance, navigation, and control operations, provides power conditioning and computer resources which stores and prioritizes science data for downlink; the Radio-Frequency (RF) Module, which provides telemetry uplink and science data downlink capabilities; and a highly capable suite of remote-sensing and in-situ instruments (Figure 2) to achieve the science objectives of the mission. The spacecraft is solar-powered with large batteries for use during the flyby and playback periods, uses reaction wheels for precise attitude control, and has a bipropellant system for propulsion and coarse attitude control. The Avionics Module consists of a radiation vault, nadir platform, and secondary structures. The module supports multiple instruments, components, and elements from other modules. The vault provides radiation protection and thermal interface control to internal electronics, and mounting support for various external instruments and spacecraft components. The telecom system includes a high-gain antenna for communication at X- or Ka-band, a co-aligned medium-gain, three low-gain antennas, and three fan beam antennas.Figure 1: Europa Clipper flight systemInstrumentation: The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft’s telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. All instruments are body mounted, and the spacecraft points the remote sensing instruments toward nadir during most of the flybys, while the in-situ instruments face the ram direction at closest approach. The MISE instrument has an internal mirror that further allows it to scan along-track to compensate for target motion when close to Europa. The narrow-angle camera has a two-axis gimbal to allow for acquisition of stereo coverage and to extend its field of regard to off-nadir targets.Figure 2: Europa Clipper suite of instrumentsMission Status: The assembly, testing, and launch operations (ATLO) phase is in its final stage. System-level testing has been completed at the Jet Propulsion Laboratory, and the flight system has been integrated with the solar array at Kennedy Space Center. The Operations and Mission Readiness Reviews have been successfully completed, and the Europa Clipper will be encapsulated in the Falcon 9 Heavy rocket in early October. The launch period begins on 10 October 2024, and once lifted off, the Europa Clipper will be cruising to the Jupiter System with gravity assists by Mars followed by Earth on the way. Go Europa Clipper!

The NASA Europa Clipper mission [1] will explore Jupiter’s icy moon Europa via multiple flybys in the early 2030s. The ocean world Europa is one of the most promising locations to search for life elsewhere in the Solar System [2, 3, 4, 5] and thus, Europa Clipper’s main goal is to characterize Europa’s habitability. In the future, a follow-on landed mission may possibly explore Europa from its surface. In the Europa Clipper science team, the work of the Reconnaissance Focus Group has been to assess the trajectory for opportunities [6]. Here we show that 12 of the 49 currently planned flybys for the prime mission of Europa Clipper [7] survey at least one area where the fundamental requirements for terrain relative navigation (TRN) are fulfilled. We use the term ‘reconable’ to refer to these 12 flybys.What is a “reconable” flyby? A ‘reconable’ flyby contains at least one section where the following fundamental (i.e., architecture independent) requirements for terrain relative navigation (TRN) are fulfilled, as based on current technology [8, 9]:Time of day: the data must be taken during the Europan day (i.e. lit by sunlight) Incidence angle of data: 30°- 60° for TRN process to be successful, 20°- 30° may be usable in some instances, but there is a rapid degradation above 60°. Altitude: 50-100 km for sufficiently high spatial resolution data with minimal smearing. 100-105 km altitude may be useable in some instances. Thus, only 12 of the 49 flybys are reconable.Fig. 1: Global map of Europa with the footprint of all 49 flybys currently planned for Europa Clipper’s prime mission. Reconable and supporting flybys are in solid colored lines. Most promising flybysUsing data from the Galileo mission, we study what is currently known about our reconable areas, and rank these flybys based on scientific criteria. The current rankings reflect our present-day knowledge and are highly likely to change with Europa Clipper’s in-depth study of the moon’s geological, geochemical and geophysical characteristics. Three of them have exceptional scientific interest. They all show signs of recent activity and have been covered significantly enough by past missions to make a comprehensive assessment of their potential. Some highlights include Fig. 2: Ground track for planned E5 flyby. Reconable area highlighted by white box. Fig. 3: Ground track for planned E19 flyby. Reconable area highlighted by white box. Fig. 4: Ground track for planned E22 flyby. Reconable area highlighted in white box. ConclusionReconable flybys are relatively rare and important in the prime mission of Europa Clipper: only 12 out of 49. It’s important to recognize that this current assessment is limited by the data available. Rankings will probably evolve as the data from Europa Clipper, and particularly from the Europa Imaging System (EIS) [10] gets processed. This work demonstrates the process that can be used by the Europa Clipper team to assess potential landing sites. Great potential landing sites do exist: there are places on Europa’s surface that are both particularly scientifically interesting (e.g., rank 1* reconable flybys) AND where we will collect data that is suitable for enabling safe and successful landing based on current technologies.The results of this work have been shared with the Geology Working Group (Pappalardo et al. 2024 (under review), Daubar et al. 2024) / the broader science team of Europa Clipper, and will be integrated in the science input provided for observation planning. AcknowledgementsThis work was supported by the Europa Clipper Project. The research described in this manuscript was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Our team would also like to acknowledge the work from the Galileo instrumental teams and the PDS imaging node for making this data publicly available.References[1] Howell & Pappalardo, Nature Comm, 2020.[2] Pappalardo et al. JGR: Planets, 1999.[3] Carr et al. Nature 1998.[4] Vance et al. JGR: Planets, 2018.[5] Cockrell et al. Astrobiology, 2016.[6] Phillips et al. PSJ, in revision.[7] Pappalardo et al. SSR, accepted.[8] Johnson et al. AIAA Guidance, Navigation, and Control Conference, 2015.[9] Neleseen et al. IEEE Aerospace Conference, 2019.[10] Turtle et al. SSR under review.