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Early Evolution of Earth's Geochemical Cycle and Biosphere: Implications for Mars ExobiologyCarbon (C) has played multiple key roles for life and its environment. C has formed organics, greenhouse gases, aquatic pH buffers, redox buffers, and magmatic constituents affecting plutonism and volcanism. These roles interacted across a network of reservoirs and processes known as the biogeochemical C cycle. Changes in the cycle over geologic time were driven by increasing solar luminosity, declining planetary heat flow, and continental and biological evolution. The early Archean C cycle was dominated by hydrothermal alteration of crustal rocks and by thermal emanations of CO2 and reduced species (eg., H2, Fe(2+) and sulfides). Bioorganic synthesis was achieved by nonphotosynthetic CO2-fixing bacteria (chemoautotrophs) and, possibly, bacteria (organotrophs) utilizing any available nonbiological organic C. Responding both to abundant solar energy and to a longterm decline in thermal sources of chemical energy and reducing power, the blaspheme first developed anoxygenic photosynthesis, then, ultimately, oxygenic photosynthesis. O2-photosynthesis played a central role in transforming the ancient environment and blaspheme to the modem world. The geochemical C cycles of early Earth and Mars were quite similar. The principal differences between the modem C cycles of these planets arose during the later evolution of their heat flows, crusts, atmospheres and, perhaps, their blasphemes.
Document ID
20020052391
Document Type
Conference Paper
Authors
DesMarais, David J. (NASA Ames Research Center Moffett Field, CA United States)
Chang, Sherwood
Date Acquired
August 20, 2013
Publication Date
January 1, 1997
Subject Category
Environment Pollution
Meeting Information
Geological Society of America Meeting(Salt Lake City, UT)
Funding Number(s)
PROJECT: RTOP 344-31-01
Distribution Limits
Public
Copyright
Other