The goal of NASA’s Europa Clipper mission is to assess the habitability of Jupiter’s moon Europa. After entering Jupiter orbit in 2030, the flight system will collect science data while flying past Europa 49 times at typical closest approach distances of 25–100 km. The mission’s objectives are to investigate Europa’s interior (ice shell and ocean), composition, and geology; the mission will also search for and characterize any current activity including possible plumes. The science objectives will be accomplished with a payload consisting of remote sensing and in-situ instruments. Remote sensing investigations cover the ultraviolet, visible, near infrared, and thermal infrared wavelength ranges of the electromagnetic spectrum, as well as an ice-penetrating radar. In-situ investigations measure the magnetic field, dust grains, neutral gas, and plasma surrounding Europa. Gravity science will be achieved using the telecommunication system, and a radiation monitoring engineering subsystem will provide complementary science data. The flight system is designed to enable all science instruments to operate and gather data simultaneously. Mission planning and operations are guided by scientific requirements and observation strategies, while appropriate updates to the plan will be made tactically as the instruments and Europa are characterized and discoveries emerge. Following collection and validation, all science data will be archived in NASA’s Planetary Data System. Communication, data sharing, and publication policies promote visibility, collaboration, and mutual interdependence across the full Europa Clipper science team, to best achieve the interdisciplinary science necessary to understand Europa.

Jupiter's icy moon, Europa, harbors a subsurface liquid water ocean; the prospect of this ocean being habitable motivates further exploration of the moon with the upcoming NASA Europa Clipper mission. Key among the mission goals is a comprehensive assessment of the moon's composition, which is essential for assessing Europa's habitability. Through powerful remote sensing and in situ investigations, the Europa Clipper mission will explore the composition of Europa's surface and subsurface, its tenuous atmosphere, and the local space environment surrounding the moon. Clues on the interior composition of Europa will be gathered through these assessments, especially in regions that may expose subsurface materials, including compelling geologic landforms or locations indicative of recent or current activity such as potential plumes. The planned reconnaissance of the icy world will constrain models that simulate the ongoing external and internal processes that act to alter its composition. This paper presents the composition-themed goals for the Europa Clipper mission, the synergistic, composition-focused investigations that will be conducted, and how the anticipated scientific return will advance our understanding of the origin, evolution, and current state of Europa.

Selected in 2019 as a NASA SIMPLEx mission, Lunar Trailblazer is in implementation for flight system delivery at the end of 2022. The mission's goal is to understand the form, abundance, and distribution of water on the Moon and the lunar water cycle. Lunar Trailblazer also collects data of candidate landing sites to inform planning for future human and robotic exploration of the Moon and evaluate the potential for in situ resource utilization. Lunar Trailblazer's two science instruments, the High-resolution Volatiles and Minerals Moon Mapper (HVM3) and the Lunar Thermal Mapper (LTM) provide simultaneous high-resolution spectral imaging data to map OH/water, crustal composition, and thermophysical properties from a $100\pm 30$ km lunar polar orbit. The ∼210-kg flight system deploys from an ESPA Grande and utilizes a ∼1000 m/s $\Delta\mathrm{V}$ hydrazine chemical propulsion system, similar to that employed by GRAIL. Trailblazing elements include the novel state-of-the-art dataset collected at substantially reduced price point, fully geographically co-registered data products delivered to the Planetary Data System, planetary mission team demographics, Caltech campus mission operations, and student staffing of select mission ops roles. Lunar Trailblazer's pioneering development is providing key lessons learned for future planetary small spacecraft.

DEVELOPMENT STATUS Diana L Blaney1, Charles Hibbitts2, Robert O Green1, Roger Nelson Clark3, James B Dalton4, Ashley Gerard Davies1, Yves Langevin5, Jonathan I Lunine6, Matthew Hedman7, Thomas B McCord8, Scott L Murchie2, Chris P Paranicas2, Frank P Seelos IV2, Jason M Soderblom9, Serina Diniega1, Morgan L Cable1, David R. Thompson1, and the MISE Engineering Team. (1)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (2)JHU-APL, Laurel, MD, United States, (3)Planetary Science Institute Tucson, Tucson, AZ, United States, (4)Self Employed, United States, (5)JPL, Pasadena, CA, United States, (5) Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France. (6)Cornell University, Department of Astronomy, Ithaca, NY, United States, (7)University of Idaho, Physics, Moscow, ID, United States, (8)Bear Fight Institute, Winthrop, WA, United States, (9)MIT, Cambridge, MA, United States.

WITH THE LUNAR TRAILBLAZER MISSION. R. L. Klima1 (Rachel.Klima@jhuapl.edu), B. L. Ehlmann2,3, D. L. Blaney3, N. E. Bowles4 S. Calcutt4, J. Dickson2, K. L. Donaldson Hanna4,5, C. S. Edwards6, R. Evans4, R. Green3, W. Frazier3, R. Greenberger2, M. A. House7, C. Howe8, J. Miura2, C. Pieters9, M. Sampson10, R. Schindhelm10, E. Scheller2, C. Seybold3, D. R. Thompson3, J. Troeltzsch10, T. J. Warren1, K. Shirley1, and J. Weinberg10. 1Johns Hopkins Applied Physics Laboratory, Laurel, MD, 2California Institute of Technology, Pasadena, CA, US, 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, US, 4Department of Physics, University of Oxford, UK, US, 5Department of Physics, University of Central Florida, Orlando, FL, US, 6Northern Arizona University, Flagstaff, AZ, US, 7Pasadena City College, Pasadena, CA, US, 8STFC RAL Space, Didcot, UK, 9Brown University, Providence, RI, US, 10Ball Aerospace & Technologies Corporation, Boulder, CO, US.

TRAILBLAZER MISSION. D. R. Thompson1, R. O. Green1, B.L. Ehlmann1,2, R. Klima4, C. Pieters3, D. Blaney1, W. Williamson1, P. Mouroulis1, N. Bowles5, S. Calcutt5, M. Cannella6, J. Dickson2, K. Donaldson-Hanna7, C. Edwards8, R. Evans5, W. Frazier1, M.A. House8, C. Howe9, B. Marotta5, J. Miura1, M. Sampson5, E. Scire1, R. Schindhelm5, C. Seybold1, K. Shirley5, J. Troelzsch6, T. Warren5, J. Weinberg6. 1Jet Propulsion Laboratory, California Institute of Technology, 2California Institute of Technology, 3Brown University, 4Johns Hopkins Applied Physics Laboratory, 5Department of Physics, University of Oxford, UK, 6Ball Aerospace & Technologies Corporation, Boulder, CO, USA, 7Univ. of Central Florida, Orlando, FL, 8Northern Arizona Univ., Flagstaff, AZ

S.M. Clegg, J. Frydenvang, R.B. Anderson, D.T. Vaniman, P. Gasda, O. Forni, H. Newsom, D. Blaney, S. Maurice, R.C. Wiens, Los Alamos National Laboratory, Los Alamos, NM, sclegg@lanl.gov, Univ. of Copenhagen, Copenhagen, Denmark, USGS, Flagstaff, AZ, Planetary Science Institute, Tucson, AZ, Institut de Recherches en Astrophysique et Planétologie, Toulouse, France, University of New Mexico, Albuquerque, NM, Jet Propulsion Laboratory, Pasadena, CA,

ChemCam is an active remote sensing instrument suite that has operated successfully on MSL since landing Aug. 6th, 2012. It uses laser pulses to remove dust and to analyze rocks up to 7 m away. Laser-induced breakdown spectroscopy (LIBS) obtains emission spectra of materials ablated from the samples in electronically excited states. The intensities of the emission lines scale with the abundances of the related element. ChemCam is sensitive to most major rock-forming elements as well as to a set of minor and trace elements such as F, Cl, Li, P, Sr, Ba, and Rb. The measured chemical composition can then be used to infer the mineralogical composition of the ablated material. Here, we report a summary of inferred apatite detections along the MSL traverse at Gale Crater. We present the geologic settings of these findings and derive some interpretations about the formation conditions of apatite in time and space.