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How do the Properties of Allan Hills 84001 Compare With Accepted Criteria for Evidence of Ancient Life?Criteria for Past Life: To be confident that any sample contains evidence of past life or biogenic activity, one must determine beyond a shadow of a doubt that certain well-established features or biomarker signatures are present in the sample. In the case of martian samples, the criteria for past life have not been established because if life existed on the planet, we have no way of knowing its detailed characteristics. Lacking independent evidence about the nature of possible past life on Mars, the scientific community must use, for the time being, the criteria established for ancient samples from the Earth: (1) Do we know the geologic context of the sample? Is it compatible with past life? (2) Do we know the age of the sample and its stratigraphic location? Are they understood enough to relate possible life to geologic history? (3) Does the sample contain evidence of cellular morphology? (4) What structural remains of colonies or communities exist within the samples? (5) Is there any evidence of biominerals showing chemical or mineral disequilibria? (6) Is there any evidence of stable isotope patterns unique to biology? (7) Are there any organic biomarkers present? (8) Are the features indigenous to the sample? For acceptance of past life in a geologic sample, essentially all of these criteria must he met.
Document ID
Acquisition Source
Johnson Space Center
Document Type
Gibson, E. K., Jr.
(NASA Johnson Space Center Houston, TX United States)
McKay, D. S.
(NASA Johnson Space Center Houston, TX United States)
Thomas-Keprta, K.
(Lockheed Martin Corp. Houston, TX United States)
Westall, F.
(NASA Johnson Space Center Houston, TX United States)
Romanek, C. A.
(Savannah River Ecology Lab. Aiken, SC United States)
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
Lunar And Planetary Exploration
Distribution Limits
Work of the US Gov. Public Use Permitted.

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