¹Liam S. T. McGovern, ¹Bruce L. A. Charlier, ¹Colin J. N. Wilson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14278]
¹School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand
Published by arrangement with John Wiley & Sons

Stepwise acid leaching experiments were performed on the pre-rain CM2 fall Aguas Zarcas to interrogate release patterns and isolate fractions with isotopic anomalies. Acid leachates and a bulk sample were analyzed for elemental abundances via solution ICP-MS, and Sr and Ba isotopic compositions were measured using TIMS. Isotopic systematics reveal diverse values for the bulk sample and leachates, interpreted to reflect the Aguas Zarcas parent body history. Compared with the NBS987 standard, μ84Sr values for the bulk sample average + 90, while the leach fractions yield +326 to −2089, with the largest μ84Sr depletions in the strongest acid leachates. For Ba isotopes, the bulk sample shows resolvable depletions (μ values) in 130Ba (−210), 135Ba (−64), 137Ba (−73) and 138Ba (−89). Early leachates show positive anomalies in 130Ba (up to +2295), 132Ba, 135Ba, 137Ba, and 138Ba. In contrast, final leachates show strong depletions for the same nuclides (up to −60,000 ppm μ130Ba). The Sr and Ba isotopic anomalies found in the earlier leachates suggest that nucleosynthetic signatures were redistributed to more soluble phases during parent body alteration. Moreover, contrasting p-nuclide Sr and Ba nucleosynthetic anomalies suggest that presolar contributions came from a variety of nucleosynthetic sources, including possibly a rotating massive star undergoing a core-collapse supernova or an electron capture supernova.

¹Marie Kepp, ^1,2,3Lu Pan, ¹Jens Frydenvang, ¹Martin Bizzarro
Earth and Planetary Science Letters 648, 119082 Link to Article [https://doi.org/10.1016/j.epsl.2024.119082]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Copenhagen, Denmark
²School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, PR China
³Deep Space Exploration Laboratory, Hefei 230026, PR China
Copyright Elsevier

The Mars Science Laboratory has been investigating the central mound of Gale crater since 2012 and revealed evidence of silica enrichment in several locations, suggesting that the geologic processes related to the formation of hydrated silica could be widespread. A reanalysis of orbital data over Aeolis Mons indicates the existence of an extensive unit rich in hydrated silica. These silica-enriched deposits, found at the base of Aeolis Mons, span elevations from -4513 m to -3351 m. The mapped hydrated silica deposits are spatially adjacent to an erosion-resistant capping unit, previously mapped as the mound skirting unit, which lies beneath the terminal deposits from local canyons and valleys. We hypothesize that the hydrated silica-bearing unit precipitated from groundwater which migrated upwards or deposited as a volcaniclastic silica-rich layer which was rehydrated during the late-stage canyon and valley forming events. The silica-bearing unit beneath the capping unit is protected against erosion by younger fan-shaped deposits and became exposed only recently. The mineralogy and stratigraphic relations with Mount Sharp units imply that the aqueous activities leading to silica diagenesis were likely a basin-wide process that occurred long after the formation of lakes in Gale crater’s geological history and experienced limited water-rock interaction since then.