NTRS - NASA Technical Reports Server

Back to Results
Terrestrial Biomarkers for Early Life on Earth as Analogs for Possible Martian Life Forms: Examples of Minerally Replaced Bacteria and Biofilms From the 3.5 - 3.3-Ga Barberton Greenstone Belt, South AfricaThe search for extraterrestrial life and especially martian life hinges on a variety of methods used to identify vestiges of what we could recognize as life, including chemical signatures, morphological fossils, and biogenic precipitates. Although the possibility of extant life on Mars (subsurface) is being considered, most exploration efforts may be directed toward the search for fossil life. Geomorphological evidence points to a warmer and wetter Mars early on in its history, a scenario that encourages comparison with the early Earth. For this reason, study of the early terrestrial life forms and environment in which they lived may provide clues as to how to search for extinct martian life. As a contribution to the early Archean database of terrestrial microfossils, we present new data on morphological fossils from the 3.5-3.3-Ga Barberton greenstone belt (BGB), South Africa. This study underlines the variety of fossil types already present in some of the oldest, best-preserved terrestrial sediments, ranging from minerally replaced bacteria and bacteria molds of vaRious morphologies (coccoid, coccobacillus, bacillus) to minerally replaced biofilm. Biofilm or extracellular polymeric substance (EPS) is produced by bacteria and appears to be more readily fossilisable than bacteria themselves. The BGB fossils occur in shallow water to subaerial sediments interbedded with volcanic lavas, the whole being deposited on oceanic crust. Penecontemporaneous silicification of sediments and volcanics resulted in the chertification of the rocks, which were later subjected to low-grade metamorphism (lower greenschist).
Document ID
Acquisition Source
Johnson Space Center
Document Type
Westall, F.
(NASA Johnson Space Center Houston, TX United States)
McKay, D. S.
(NASA Johnson Space Center Houston, TX United States)
Gibson, E. K.
(NASA Johnson Space Center Houston, TX United States)
deWit, M. J.
(Cape Town Univ. Rondebosch, South Africa)
Dann, J.
(Cape Town Univ. Rondebosch, South Africa)
Gerneke, D.
(Cape Town Univ. Rondebosch, South Africa)
deRonde, C. E. J.
(Institute of Geological and Nuclear Sciences Ltd. Lower Hutt, New Zealand)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Publication Information
Publication: Workshop on the Issue Martian Meteorites: Where do we Stand and Where are we Going?
Subject Category
Life Sciences (General)
Distribution Limits
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available