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Microscopic physical biomarkers in carbonate hot springs: implications in the search for life on MarsPhysical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms--submillimeter to submicrometer. The four moderate-temperature (57 to 72 degrees C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditions. Some of the microbes coexist with travertine deposits in endolithic communities. In other cases, the microbes are rapidly coated and destroyed by precipitates but leave distinctive mineral fabrics. Some microbes adapted to carbonate hot springs produce an extracellular polymeric substance which forms a three-dimensional matrix with living cells and cell remains, known as a biofilm. Silicon and iron oxides often coat the biofilm, leading to long-term preservation. Submicrometer mineralized spheres composed of calcium fluoride or silica are common in carbonate hot spring deposits. Sphere formation is biologically mediated, but the spheres themselves are apparently not fossils or microbes. Additionally, some microbes selectively weather mineral surfaces in distinctive patterns. Hot spring deposits have been cited as prime locations for exobiological exploration of Mars. The presence of preserved microscopic physical biomarkers at all four sites supports a strategy of searching for evidence of life in hot spring deposits on Mars.
Document ID
20040088796
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Allen, C. C.
(Lockheed Martin Space Operations, Houston, Texas 77058, United States)
Albert, F. G.
Chafetz, H. S.
Combie, J.
Graham, C. R.
Kieft, T. L.
Kivett, S. J.
McKay, D. S.
Steele, A.
Taunton, A. E.
Taylor, M. R.
Thomas-Keprta, K. L.
Westall, F.
Date Acquired
August 21, 2013
Publication Date
September 1, 2000
Publication Information
Publication: Icarus
Volume: 147
Issue: 1
ISSN: 0019-1035
Subject Category
Exobiology
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center JSC
NASA Discipline Exobiology

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