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Looking for Fossil Bacteria in Martian MaterialsThe rationale for looking for prokaryote fossils in Martian materials is based on our present understanding of the environmental evolution of that planet in comparison to the history of the terrestrial environments and the development and evolution of life on Earth. On Earth we have clear, albeit indirect, evidence of life in 3.8 b.y.-old rocks from Greenland and the first morphological fossils in 3.3-3.5 b.y.-old cherts from South Africa and Australia. In comparison, Mars, being smaller, probably cooled down after initial aggregation faster than the Earth. Consequently, there could have been liquid water on its surface earlier than on Earth. With a similar exogenous and endogenous input of organics and life-sustaining nutrients as is proposed for the Earth, life could have arisen on that planet, possibly slightly earlier dm it did on Earth. Whereas on Earth liquid water has remained at the surface of the planet since about 4.4 b.y. (with some possible interregnums caused by planet-sterilising impacts before 3.8. b.y. and perhaps a number of periods of a totally frozen Earth, this was not the case with Mars. Although it is not known exactly when surficial water disappeared from the surface, there would have been sufficient time for life to have developed into something similar to the terrestrial prokaryote stage. However, given the earlier environmental deterioration, it is unlikely that it evolved into the eukaryote stage and even evolution of oxygenic photosynthesis may not have been reached. Thus, the impetus of research is on single celled life simnilar to prokaryotes. We are investigating a number of methods of trace element analysis with respect to the Early Archaean microbial fossils. Preliminary neutron activation analysis of carbonaceous layers in the Early Archaean cherts from South Africa and Australia shows some partitioning of elements such as As, Sb, Cr with an especial enrichment of lanthanides in a carbonaceous-rich banded iron sediment . More significantly, preliminary TOF-SIMS investigations of organics in the cherts reveals the presence of a biomarker, which appears to be a derivative of bacterial polymer, in the carbonaceous parts of the rocks. We conclude that a combination of morphological, isotope and biogeochemical methods can be used to successfully identify signs of life in terrestrial material, and that these methods will be useful in searching for signs of life in extraterrestrial materials.
Document ID
20000012739
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Westall, F.
(NASA Johnson Space Center Houston, TX United States)
Walsh, M. M.
(Louisiana State Univ. Baton Rouge, LA United States)
Mckay, D. D.
(NASA Johnson Space Center Houston, TX United States)
Wentworth, S.
(Lockheed Martin Corp. Houston, TX United States)
Gibson, E. K.
(NASA Johnson Space Center Houston, TX United States)
Steele, A.
(NASA Johnson Space Center Houston, TX United States)
Toporski, J.
(Portsmouth Univ. Portsmouth, United Kingdom)
Lindstrom, D.
(NASA Johnson Space Center Houston, TX United States)
Martinez, R.
(Lockheed Martin Corp. Houston, TX United States)
Allen, C. C.
(Lockheed Martin Corp. Houston, TX United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Workshop on Mars 2001: Integrated Science in Preparation for Sample Return and Human Exploration
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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