Letter abstract
Nature Geoscience 1, 355 - 358 (2008)
Published online: 18 May 2008 | doi:10.1038/ngeo207
Subject Category: Planetary science
Clay minerals in delta deposits and organic preservation potential on Mars
Bethany L. Ehlmann1, John F. Mustard1, Caleb I. Fassett1, Samuel C. Schon1, James W. Head III1, David J. Des Marais2, John A. Grant3 & Scott L. Murchie4
Clay-rich sedimentary deposits are often sites of organic matter preservation1, 2, and have therefore been sought in Mars exploration3. However, regional deposits of hydrous minerals, including phyllosilicates and sulphates4, 5, are not typically associated with valley networks and layered sediments that provide geomorphic evidence of surface water transport on early Mars6, 7, 8. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)9 has recently identified phyllosilicates10 within three lake basins with fans or deltas that indicate sustained sediment deposition: Eberswalde crater7, 11, 12, Holden crater12, 13 and Jezero crater14. Here we use high-resolution data from the Mars Reconnaissance Orbiter (MRO) to identify clay-rich fluvial–lacustrine sediments within Jezero crater, which has a diameter of 45 km. The crater is an open lake basin on Mars with sedimentary deposits of hydrous minerals sourced from a smectite-rich catchment in the Nili Fossae region. We find that the two deltas and the lowest observed stratigraphic layer within the crater host iron–magnesium smectite clay. Jezero crater holds sediments that record multiple episodes of aqueous activity on early Mars. We suggest that this depositional setting and the smectite mineralogy make these deltaic deposits well suited for the sequestration and preservation of organic material.
- Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA
- NASA Ames Research Center, Mountain View, California 94035, USA
- Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20013, USA
- Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland 20723, USA
Correspondence to: Bethany L. Ehlmann1 e-mail: bethany_ehlmann@brown.edu
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