Microscopic Physical Biomarkers in Carbonate Hot Springs: Implications in the Search for Life on Mars

Authors: Allen C.C.¹; Albert F.G.²; Chafetz H.S.³; Combie J.²; Graham C.R.⁴; Kieft T.L.⁵; Kivett S.J.⁶; McKay D.S.⁷; Steele A.⁸; Taunton A.E.⁹; Taylor M.R.¹⁰; Thomas-Keprta K.L.¹¹; Westall F.¹²

Source: Icarus, Volume 147, Number 1, September 2000 , pp. 49-67(19)

Publisher: Academic Press

Abstract:

Physical 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°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. Copyright 2000 Academic Press.

Language: English

Document Type: Research article

Affiliations: 1: Lockheed Martin Space Operations, Mail Code C23, Houston, Texas, 77058 10: Henderson State University, Arkadelphia, Arkansas 11: Lockheed Martin Space Operations, Houston, Texas 12: Lunar and Planetary Institute, Houston, Texas 2: Montana Biotech Corporation, Belgrade, Montana 3: University of Houston, Houston, Texas 4: Harvard University, Cambridge, Massachusetts 5: New Mexico Institute of Mining and Technology, Socorro, New Mexico 6: University of Washington, Seattle, Washington 7: NASA Johnson Space Center, Houston, Texas 8: University of Portsmouth, Portsmouth, United Kingdom 9: University of Wisconsin, Madison, Wisconsin

Publication date: 2000-09-01

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• In this Subject: Astronomy
• By this author: Allen C.C. ;  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.

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