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GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 144-4
Presentation Time: 2:25 PM

SURFICIAL EVIDENCE FOR THE VARIED SOURCES OF FACULAE-FORMING BRINES IN OCCATOR CRATER


SCULLY, Jennifer E.C.1, SCHENK, Paul M.2, CASTILLO-ROGEZ, Julie C.1, BUCZKOWSKI, Debra L.3, WILLIAMS, David A.4, PASCKERT, Jan Hendrik5, DUARTE, Kayla6, ROMERO, Vivian N.7, QUICK, Lynnae C.8, SORI, Michael M.9, LANDIS, Margaret E.10, RAYMOND, Carol A.11, NEESEMANN, Alicia12, SCHMIDT, Britney E.13, SIZEMORE, Hanna G.14 and RUSSELL, Christopher T.15, (1)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, (2)Lunar and Planetary Institute, Houston, TX 77058, (3)Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, (4)School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, (5)Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, Münster, 48149, Germany, (6)School of Earth & Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, (7)Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr, Atlanta, GA 30318, (8)Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, (9)Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, (10)Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO 80303, (11)NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, (12)Freie Universität Berlin, Berlin, 12249, Germany, (13)Georgia Institute of Technology, Atlanta, GA 30332, (14)Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, (15)Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095

Dawn observed enigmatic faculae (bright regions) in Occator crater (Russell+, 2016). The faculae are mostly composed of sodium carbonate and ammonium chloride, consistent with the remnants of brines sourced in the subsurface (De Sanctis+, 2016; Raponi+, 2019). Low elliptical orbits provided up to ~3 m/pix Framing Camera images of Occator from as low as ~35 km. We use this data to create a new, highest resolution geologic map of Occator and its faculae. We find that the faculae were emplaced via brine effusion: hydrothermal deposits were emplaced ballistically and as flows, which originated from numerous localized sources of brine that were unresolved in previous data. Many characteristics of the faculae resemble those of terrestrial/Martian hydrothermal deposits (Osinski+, 2013), including an association with fractures and the crater center (which would remain hottest for the longest time). A complex hydrologic plumbing system of fracture and hydrologic networks can explain the deposition of Pasola Facula (PF) on a ledge about the central pit, which contains Cerealia Facula (CF). Both CF and PF were sourced in an impact-induced melt chamber, which is predicted to have formed under the Occator's center (Bowling+, 2019). Our mapping shows that the availability of the faculae-forming brines varied on short spatial scales, and that the system was often brine-limited. Vinalia Faculae (VF) are located in the eastern crater floor, too far from the crater center to be sourced in the impact-induced melt chamber. Instead, VF could be sourced by a deep, long-lived brine reservoir, which existed before the Occator-forming impact and is predicted from thermal modeling (Castillo+, 2019). Surficial evidence for this hypothesis is that VF are significantly thinner and less voluminous than CF. This is consistent with the VF-forming brines, sourced in the deep brine reservoir, taking a longer and more difficult path to the surface than the CF-forming brines, which were locally fed from the shallower impact-inducted melt chamber. In both cases, pathways to the surface were opened by the prevalent impact-induced fracturing throughout the crater (Raymond+, submitted). Part of this work is being carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged.

Session No. 144

T90. The Big Picture from Small Bodies: Dwarf Planets, Asteroids, and Comets
Monday, 23 September 2019: 1:30 PM-5:30 PM
Room 232BC, North Building (Phoenix Convention Center)
Geological Society of America Abstracts with Programs. Vol. 51, No. 5
doi: 10.1130/abs/2019AM-339505
© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
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