Biology
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p53a..04q&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P53A-04
Biology
0406 Astrobiology And Extraterrestrial Materials, 0456 Life In Extreme Environments, 0471 Oxidation/Reduction Reactions (4851), 1060 Planetary Geochemistry (5405, 5410, 5704, 5709, 6005, 6008), 5494 Instruments And Techniques
Scientific paper
Thirty years ago, the Viking Landers were sent to Mars to search for evidence of life. With Viking Gas Exchange (GEx) experiment, an attempt was made to identify microbial activity in the martian surface material by using gas chromatography to measure gas changes in the headspace above a soil sample after the addition of an aqueous nutrient medium. The results of GEx experiment indicate that the surface material at the Viking sites was chemically reactive but not biologically active. We have performed the Viking Gas Exchange (GEx) experiment on soil samples collected from 22 locations in the "Mars-like" Yungay region of the Atacama Desert. Although we detect the presence of non-biological oxidative processes, in the majority of Yungay samples, the dominant process is biological. Within 10 days of incubation in the GEx experiment, samples from 20 of the 22 sites tested positive for life. These results contrast with the significantly lower levels of culturable organisms in Yungay soils that have been detected using other methods (Navarro-Gonzalez et al. 2003; Conley et al. 2006). These results also present a potential discrepancy between the presence of detectable biology and the apparent lack of recoverable DNA and low levels of detectable organic compounds in these soils (Navarro-Gonzalez et al.2003; Skelley et al. 2005). This discrepancy may be explained in part by organic chemical loss mechanisms (including oxidation and aqueous transport) in these soils. We discuss our results in the context of the other Viking experiments (the Viking GCMS and Labeled Release experiments) and the limitations of current state-of-the-art approaches to life detection and organic chemical analysis. Conley, C.A., et al., Astrobiology, 6, 521-526, 2006; Navarro-Gonzales, R., et al., Science, 302 1018-1021, 2003; Skelley, A.M., et al., PNAS, 102, 1041-1046, 2006.
Pan Deng
Quinn Richard
Taylor Charles
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