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A Strategy for Mars ExopaleontologyThere is compelling geological evidence that the climate of early Mars was much more Earth-like, with a denser atmosphere and abundant surface water. Given that life developed on the Earth very quickly (between 4.2 and 3.5 Ga), it is quite plausible that life may have also developed on Mars during this early clement period. If Martian life developed, it is likely to have left behind a fossil record. Thus, an important focus for upcoming Mars missions is to explore for an ancient biosphere. This presents a set of goals and problems that are quite distinct from Exobiology. I call this new activity "Exopaleontology", whose core principles derive from studies of the Precambrian fossil record on Earth, biosedimentology and microbial fossilization. Such studies reveal that the most important factor favoring the long-term preservation of microbial fossils is rapid entombment of microorganisms by fine-grained, stable mineral phases such as silica, phosphate, carbonate and metal sulfides. Terrestrial environments where such aqueous mineral phases frequently entomb and preserve microorganisms include subaerial and subaqueous springs and shallow hydrothermal systems, evaporitic alkaline lakes, "hardpan" soils (e.g. calcretes, silcretes, ferracretes), and frozen soils or ground ice. With the exception of ice, which has a short crustal residence time, such deposits am known to retain a record of terrestrial life for billions of years. Current activities seek to refine and apply this strategy to the Mars Global Surveyor missions and beyond. Ongoing studies of microbial fossilization in each of the target environments identified above are aimed at improving our understanding of how biological information is incorporated into aqueous mineral deposits and preserved. Viking data is being used to target sites for high resolution orbital imaging and spectroscopy during upcoming Mars missions. Such data will provide a basis for selecting sites for future landed missions and eventually, sample return.
Document ID
20020033430
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Farmer, Jack D.
(NASA Ames Research Center Moffett Field, CA United States)
DesMarais, David J.
(NASA Ames Research Center Moffett Field, CA United States)
Chang, Sherwood
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Lunar And Planetary Science And Exploration
Meeting Information
Meeting: Geological Society of America 1995 Fall Meeting
Location: New Orleans, LA
Country: United States
Start Date: November 6, 1995
End Date: November 9, 1995
Sponsors: Geological Society of America
Funding Number(s)
PROJECT: RTOP 185-52-32
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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