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Late-stage formation of Martian chloride salts through ponding and evaporation

Brian M. Hynek, Mikki K. Osterloo and Kathryn S. Kierein-Young
Late-stage formation of Martian chloride salts through ponding and evaporation
Geology (Boulder) (August 2015) 43 (9): 787-790


Small deposits of chloride salts have been documented at hundreds of locations on Mars through the use of multispectral orbital data. Given the small spatial extent of these deposits, their formation mechanisms, timing, and relation to other aqueous processes in Mars' history are presently poorly constrained. Here we detail one of the chloride deposits near Meridiani Planum, the location of the Opportunity rover. This chloride deposit likely formed from fluviolacustrine processes, implying an active hydrologic cycle. Late-stage activity led to valley incision in the surrounding highlands and ponding of water to form a lake in a local basin. The lake level eventually rose and breached the drainage divide, leading to significant outflow. The remaining water evaporated and eventually precipitated the chlorides at the lowest levels. Through digital terrain models, the lake and salt flat volumes were used to calculate the salinity of the lake, which at full lake extent was approximately 8% of the salinity of Earth's oceans. Crater density measurements on the terrain cross-cut by the outlet valley constrain the maximum age to 3.60 Ga. This hydrological episode occurred after regional widespread fluvial incision and also post-dates formation of the sulfate bedrock being investigated by Opportunity. We conclude that this and other similar chloride deposits represent some of the last vestiges of habitable surface water on Mars as recorded in the mineralogical record.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 9
Title: Late-stage formation of Martian chloride salts through ponding and evaporation
Affiliation: University of Colorado-Boulder, Department of Geological Sciences, Boulder, CO, United States
Pages: 787-790
Published: 20150805
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2015-087065
Categories: Extraterrestrial geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015269
Illustration Description: illus. incl. geol. sketch map
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201537
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