Determining the internal structure of Uranus is a key objective for planetary science. Knowledge of Uranus’s bulk composition and the distribution of elements is crucial to understanding its origin and evolutionary path. In addition, Uranus represents a poorly understood class of “intermediate-mass planets” (intermediate in size between the relatively well studied terrestrial and gas giant planets), which appear to be very common in the Galaxy. As a result, a better characterization of Uranus will also help us to better understand exoplanets in this mass and size regime.
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Recognizing the importance of Uranus, a Keck Institute for Space Studies (KISS) workshop was held in September 2023 to investigate how we can improve our knowledge of Uranus’s internal structure in the context of a future Uranus mission that includes an orbiter and a probe. The scientific goals and objectives of the recently released Planetary Science and Astrobiology Decadal Survey were taken as our starting point. We reviewed our current knowledge of Uranus’s interior and identified measurement and other mission requirements for a future Uranus spacecraft, providing more detail than was possible in the Decadal Survey’s mission study and including new insights into the measurements to be made. We also identified important
knowledge gaps to be closed with Earth-based efforts in the near term that will help guide the design of the mission and interpret the data returned.
Our report focuses on the following topics:
• Uranus’s atmosphere (noble gas, elemental, and molecular abundances and the pressure-temperature profile)
• Its gravity field and interior models
• The planet’s magnetic field, heat flux, and energy balance
• The potential for Uranian seismology
In the words of the Decadal Survey, the Uranus Flagship mission can produce “transformative, breakthrough science across a broad range of topics.” We argue that to fulfill its promise, great progress should be made in terms of mission design, theoretical calculations, numerical modeling, experiments, ground-based observations, and bringing communities together to plan the mission and interpret the data it returns.
", "doi": "10.7907/1k6kh-fjs61", "publisher": "Keck Institute for Space Studies", "publication_date": "2024-09-03" }, { "id": "authors:bjfe5-72f35", "collection": "authors", "collection_id": "bjfe5-72f35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220222-212156808", "type": "monograph", "title": "Revolutionizing Access to the Mars Surface", "author": [ { "family_name": "Culbert", "given_name": "Christopher J.", "clpid": "Culbert-Christopher-J" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Fraeman", "given_name": "Abigail A.", "orcid": "0000-0003-4017-5158", "clpid": "Fraeman-Abigail-A" }, { "family_name": "Albert", "given_name": "Sam", "orcid": "0000-0002-7013-7649", "clpid": "Albert-Samuel-W" }, { "family_name": "Banfield", "given_name": "Don", "orcid": "0000-0003-2664-0164", "clpid": "Banfield-Don" }, { "family_name": "Bapst", "given_name": "Jonathan", "orcid": "0000-0003-1176-7613", "clpid": "Bapst-Jonathan" }, { "family_name": "Bearden", "given_name": "Dave", "clpid": "Bearden-David-A" }, { "family_name": "Bonnet", "given_name": "Kevin", "clpid": "Bonnet-Kevin" }, { "family_name": "Burdick", "given_name": "Joel", "orcid": "0000-0002-3091-540X", "clpid": "Burdick-J-W" }, { "family_name": "Calvin", "given_name": "Wendy", "orcid": "0000-0002-6097-9586", "clpid": "Calvin-Wendy-M" }, { "family_name": "Cohen", "given_name": "Barbara", "orcid": "0000-0001-5896-5903", "clpid": "Cohen-Barbara-A" }, { "family_name": "Crain", "given_name": "Tim", "clpid": "Crain-Tim" }, { "family_name": "Edwards", "given_name": "Charles (Chad)", "orcid": "0000-0001-5835-0044", "clpid": "Edwards-Charles-Chad" }, { "family_name": "Falcone", "given_name": "Giusy", "clpid": "Falcone-Giusy" }, { "family_name": "Frank", "given_name": "Elizabeth", "clpid": "Frank-Elizabeth" }, { "family_name": "Horchler", "given_name": "Andrew", "orcid": "0000-0002-0449-1674", "clpid": "Horchler-Andrew" }, { "family_name": "Johnson", "given_name": "Mark", "clpid": "Johnson-Mark" }, { "family_name": "Kennedy", "given_name": "Brett", "clpid": "Kennedy-Brett" }, { "family_name": "Kerber", "given_name": "Laura", "orcid": "0000-0002-6092-9722", "clpid": "Kerber-Laura" }, { "family_name": "Manning", "given_name": "Rob", "clpid": "Manning-Robert-M" }, { "family_name": "Masten", "given_name": "David", "clpid": "Masten-David" }, { "family_name": "Matthies", "given_name": "Larry", "clpid": "Matthies-Larry-H" }, { "family_name": "Munk", "given_name": "Michelle", "clpid": "Munk-Michelle" }, { "family_name": "Murrow", "given_name": "David", "clpid": "Murrow-David" }, { "family_name": "Niles", "given_name": "Paul", "orcid": "0000-0001-7612-1421", "clpid": "Niles-Paul-B" }, { "family_name": "Panning", "given_name": "Mark", "orcid": "0000-0002-2041-3190", "clpid": "Panning-Mark-P" }, { "family_name": "Putnam", "given_name": "Zachary (Zach)", "orcid": "0000-0002-0077-8555", "clpid": "Putnam-Zachary-Zach-R" }, { "family_name": "Scheller", "given_name": "Eva", "orcid": "0000-0002-9981-5802", "clpid": "Scheller-Eva-L" }, { "family_name": "Sheppard", "given_name": "Rachel", "orcid": "0000-0002-7561-9735", "clpid": "Sheppard-Rachel" }, { "family_name": "Stein", "given_name": "Nathan", "orcid": "0000-0003-3385-9957", "clpid": "Stein-Nathaniel-T" }, { "family_name": "Wei", "given_name": "Skylar", "clpid": "Wei-Skylar-X" }, { "family_name": "Woolley", "given_name": "Ryan", "orcid": "0000-0003-1641-0621", "clpid": "Woolley-Ryan-C" }, { "family_name": "Wooster", "given_name": "Paul", "clpid": "Wooster-Paul" } ], "abstract": "Under the auspices of the Keck Institute for Space Studies at Caltech, we convened a group of Mars scientists and engineers, representing multiple academic institutions, NASA Centers, and commercial companies in March 2021 to address the challenge of revolutionizing access to the Mars surface. Following a 3-month summer study period where working groups addressed specific programmatic, cultural, and engineering challenges, we then convened a second workshop in September 2021. The report that follows represents the product of the\ndiscussions. \n\nWe first outline why Mars\u2014and particularly landed access to Mars\u2014is a priority over the next decades of scientific exploration (Section 1). We then review the challenges to achieving increased numbers of missions accessing the Mars surface (Section 2) as well as near-term trends in the space sector that provide means to overcome these challenges (Section 3). We then describe the intertwined elements of the Frequent, Affordable, Bold (FAB) strategy to achieve access (Section 4). Finally, we discuss the means by which a FAB strategy can be implemented, developing similar sets of science mission types and employing a services model that fosters increasing commercial capabilities over a set of the mission types (Section 5).", "doi": "10.7907/d1sm-mj77", "publisher": "California Institute of Technology", "publication_date": "2022-02" }, { "id": "authors:nb3f9-s8p96", "collection": "authors", "collection_id": "nb3f9-s8p96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201026-101616800", "type": "monograph", "title": "Controls on the Global Distribution of Martian Landsliding", "author": [ { "family_name": "Roback", "given_name": "Kevin P.", "orcid": "0000-0001-5209-2873", "clpid": "Roback-K-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" } ], "abstract": "Recent acquisition of high-resolution satellite imagery of the Martian surface has permitted landsliding to be studied on a global scale on Mars for the first time. We apply the Scoops3D software package to compute slope stability for select regions of the Martian surface, combining calculations of slope stability with number of observed landslides, as reported in a recently published (Crosta et al., 2018a, b) inventory of Martian landslides, to understand controls on the global distribution of landsliding on Mars. We find that the distribution of landsliding does not simply follow the distribution of unstable slopes. In particular, there is an increase in landsliding in the Tharsis Rise area, and especially in Valles Marineris and Noctis Labyrinthus, that is not explained by an abundance of unstable topography alone. We analyzed for but did not find a clear local lithologic or stratigraphic control on landslide occurrence from subsurface heterogeneities. Other possibilities to explain the increased occurrence of landslides in the Tharsis Rise include (1) regionally widespread Tharsis weak unit(s), such as from interbedded ashes and lavas; (2) seismic activity related to the Tharsis Rise's geological activity, and (3) possible groundwater near Valles Marineris into the Amazonian. Given the apparently young ages of many landslide deposits in Valles Marineris (Quantin et al., 2004), continued modern day analysis of lithologies in Valles Marineris and observations of Martian seismicity may act to strengthen or rebut the first two hypotheses.", "doi": "10.1002/essoar.10504190.1", "publication_date": "2020-09-10" }, { "id": "authors:gtpdj-tmm05", "collection": "authors", "collection_id": "gtpdj-tmm05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201028-085838317", "type": "monograph", "title": "Machine-Learning-Driven New Geologic Discoveries at Mars Rover Landing Sites: Jezero Crater and NE Syrtis", "author": [ { "family_name": "Dundar", "given_name": "Murat", "orcid": "0000-0001-5752-468X", "clpid": "Dundar-M" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Leask", "given_name": "Ellen K.", "orcid": "0000-0002-3220-4003", "clpid": "Leask-E-K" } ], "abstract": "A hierarchical Bayesian classifier is trained at pixel scale with spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) images. Its utility in detecting small exposures of uncommon phases is demonstrated with new geologic discoveries near the Mars-2020 rover landing site. Akaganeite is found in sediments on the Jezero crater floor and in fluvial deposits at NE Syrtis. Jarosite and silica are found on the Jezero crater floor while chlorite-smectite and Al phyllosilicates are found in the Jezero crater walls. These detections point to a multi-stage, multi-chemistry history of water in Jezero crater and the surrounding region and provide new information for guiding the Mars-2020 rover's landed exploration. In particular, the akaganeite, silica, and jarosite in the floor deposits suggest either a later episode of salty, Fe-rich waters that post-date the Jezero crater delta or groundwater alteration of portions of the Jezero crater sedimentary sequence.", "doi": "10.1002/essoar.10501294.1", "publication_date": "2019-12-18" }, { "id": "authors:3gcg3-khn91", "collection": "authors", "collection_id": "3gcg3-khn91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180426-110252898", "type": "monograph", "title": "Methane on Mars and Habitability: Challenges and Responses", "author": [ { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Chen", "given_name": "Pin", "clpid": "Chen-Pin" }, { "family_name": "Nealson", "given_name": "Kenneth", "orcid": "0000-0001-5189-3732", "clpid": "Nealson-K-H" }, { "family_name": "Atreya", "given_name": "Sushil", "orcid": "0000-0002-1972-1815", "clpid": "Atreya-S-K" }, { "family_name": "Beckett", "given_name": "Patrick", "clpid": "Beckett-P" }, { "family_name": "Blank", "given_name": "Jennifer", "clpid": "Blank-J-G" }, { "family_name": "Ehlmann", "given_name": "Bethany", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Eiler", "given_name": "John", "clpid": "Eiler-J-M" }, { "family_name": "Etiope", "given_name": "Giuseppe", "clpid": "Etiope-G" }, { "family_name": "Ferry", "given_name": "James G.", "clpid": "Ferry-J-G" }, { "family_name": "Forget", "given_name": "Francois", "clpid": "Forget-F" }, { "family_name": "Gao", "given_name": "Peter", "orcid": "0000-0002-8518-9601", "clpid": "Gao-Peter" }, { "family_name": "Hu", "given_name": "Renyu", "orcid": "0000-0003-2215-8485", "clpid": "Hu-Renyu" }, { "family_name": "Kleinb\u00f6hl", "given_name": "Armin", "clpid": "Kleinb\u00f6hl-A" }, { "family_name": "Klusman", "given_name": "Ronald", "clpid": "Klusman-R" }, { "family_name": "Lef\u00e8vre", "given_name": "Franck", "clpid": "Lef\u00e8vre-F" }, { "family_name": "Miller", "given_name": "Charles", "orcid": "0000-0002-9380-4838", "clpid": "Miller-C-E" }, { "family_name": "Mischna", "given_name": "Michael", "orcid": "0000-0002-8022-5319", "clpid": "Mischna-M-A" }, { "family_name": "Mumma", "given_name": "Michael", "clpid": "Mumma-M-J" }, { "family_name": "Newman", "given_name": "Sally", "orcid": "0000-0003-0710-995X", "clpid": "Newman-S" }, { "family_name": "Oehler", "given_name": "Dorothy", "clpid": "Oehler-D-Z" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Oremland", "given_name": "Ronald", "clpid": "Oremland-R-S" }, { "family_name": "Orphan", "given_name": "Victoria", "orcid": "0000-0002-5374-6178", "clpid": "Orphan-V-J" }, { "family_name": "Popa", "given_name": "Radu", "clpid": "Popa-R" }, { "family_name": "Russell", "given_name": "Michael", "clpid": "Russell-M-J" }, { "family_name": "Shen", "given_name": "Linhan", "orcid": "0000-0003-3871-655X", "clpid": "Shen-Linhan" }, { "family_name": "Sherwood Lollar", "given_name": "Barbara", "clpid": "Sherwood-Lollar-B" }, { "family_name": "Stamenkovi\u0107", "given_name": "Vlada", "orcid": "0000-0003-2416-3683", "clpid": "Stamenkovi\u0107-V" }, { "family_name": "Staehle", "given_name": "Robert", "clpid": "Staehle-R-L" }, { "family_name": "Stolper", "given_name": "Daniel", "orcid": "0000-0003-3299-3177", "clpid": "Stolper-D-A" }, { "family_name": "Templeton", "given_name": "Alexis", "clpid": "Templeton-A" }, { "family_name": "Vandaele", "given_name": "Ann C.", "clpid": "Vandaele-A-C" }, { "family_name": "Viscardy", "given_name": "S\u00e9bastien", "clpid": "Viscardy-S" }, { "family_name": "Webster", "given_name": "Chris", "clpid": "Webster-C-R" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Wong", "given_name": "Michael", "clpid": "Wong-Michael-L" }, { "family_name": "Worden", "given_name": "John", "orcid": "0000-0003-0257-9549", "clpid": "Worden-J-R" } ], "abstract": "Recent measurements of methane (CH_4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH_4 (\u223c0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH_4 with peak abundances of \u223c7\u2009ppbv. What do these CH_4 revelations with drastically different abundances and temporal signatures represent in terms of interior geochemical processes, or is martian CH_4 a biosignature? Discerning how CH_4 generation occurs on Mars may shed light on the potential habitability of Mars. There is no evidence of life on the surface of Mars today, but microbes might reside beneath the surface. In this case, the carbon flux represented by CH_4 would serve as a link between a putative subterranean biosphere on Mars and what we can measure above the surface. Alternatively, CH_4 records modern geochemical activity. Here we ask the fundamental question: how active is Mars, geochemically and/or biologically? In this article, we examine geological, geochemical, and biogeochemical processes related to our overarching question. The martian atmosphere and surface are an overwhelmingly oxidizing environment, and life requires pairing of electron donors and electron acceptors, that is, redox gradients, as an essential source of energy. Therefore, a fundamental and critical question regarding the possibility of life on Mars is, \"Where can we find redox gradients as energy sources for life on Mars?\" Hence, regardless of the pathway that generates CH_4 on Mars, the presence of CH_4, a reduced species in an oxidant-rich environment, suggests the possibility of redox gradients supporting life and habitability on Mars. Recent missions such as ExoMars Trace Gas Orbiter may provide mapping of the global distribution of CH_4. To discriminate between abiotic and biotic sources of CH_4 on Mars, future studies should use a series of diagnostic geochemical analyses, preferably performed below the ground or at the ground/atmosphere interface, including measurements of CH_4 isotopes, methane/ethane ratios, H_2 gas concentration, and species such as acetic acid. Advances in the fields of Mars exploration and instrumentation will be driven, augmented, and supported by an improved understanding of atmospheric chemistry and dynamics, deep subsurface biogeochemistry, astrobiology, planetary geology, and geophysics. Future Mars exploration programs will have to expand the integration of complementary areas of expertise to generate synergistic and innovative ideas to realize breakthroughs in advancing our understanding of the potential of life and habitable conditions having existed on Mars. In this spirit, we conducted a set of interdisciplinary workshops. From this series has emerged a vision of technological, theoretical, and methodological innovations to explore the martian subsurface and to enhance spatial tracking of key volatiles, such as CH_4.", "doi": "10.7907/Z990220K", "publisher": "Astrobiology", "publication_date": "2018-01" } ]