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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, E12007, doi:10.1029/2004JE002321, 2004

Poor preservation potential of organics in Meridiani Planum hematite-bearing sedimentary rocks

Dawn Y. Sumner

Geology Department, University of California, Davis, Davis, California, USA


Abstract

Life is composed of organic compounds, and characterizing preserved compounds provides insights into the presence of specific types of life, including early life on Earth. With growing evidence for a wet early Mars, excitement over the potential of an early Martian biosphere strongly motivates Mars exploration. However, the preservation potential of organic compounds in rocks on either Earth or Mars depends critically on mineralogy. Results from elemental, mineralogical, and morphological characterization of sedimentary rocks by the Opportunity rover team in the vicinity of the Challenger Memorial Station, Meridiani Planum, demonstrate an abundance of Fe(III) and sulfate minerals that formed from liquid water. The composition of these sedimentary rocks suggests that organic compounds are unlikely to be preserved within them, even if present when the rocks were deposited, based on comparisons with iron formation, acid lake deposits, and iron-containing concretions from Earth. No evidence consistent with the presence of organic compounds, such as the presence of Fe(II) minerals, has been reported from Meridiani Planum to date. Thus these Martian sedimentary rocks are not a good target to explore for organic compounds on Mars.

Received 13 July 2004; accepted 22 October 2004; published 28 December 2004.

Keywords: evaporites; hematite; organic preservation.

Index Terms: 6225 Planetology: Solar System Objects: Mars; 5470 Planetology: Solid Surface Planets: Surface materials and properties; 1045 Geochemistry: Low-temperature geochemistry; 1055 Geochemistry: Organic geochemistry; 3675 Mineralogy and Petrology: Sedimentary petrology.

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Citation: Sumner, D. Y. (2004), Poor preservation potential of organics in Meridiani Planum hematite-bearing sedimentary rocks, J. Geophys. Res., 109, E12007, doi:10.1029/2004JE002321.