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Estimates of the maximum time required to originate lifeFossils of the oldest microorganisms exist in 3.5 billion year old rocks and there is indirect evidence that life may have existed 3.8 billion years ago (3.8 Ga). Impacts able to destroy life or interrupt prebiotic chemistry may have occurred after 3.5 Ga. If large impactors vaporized the oceans, sterilized the planets, and interfered with the origination of life, life must have originated in the time interval between these impacts which increased with geologic time. Therefore, the maximum time required for the origination of life is the time that occurred between sterilizing impacts just before 3.8 Ga or 3.5 Ga, depending upon when life first appeared on earth. If life first originated 3.5 Ga, and impacts with kinetic energies between 2 x 10 the the 34th and 2 x 10 to the 35th were able to vaporize the oceans, using the most probable impact flux, it is found that the maximum time required to originate life would have been 67 to 133 million years (My). If life originated 3.8 Ga, the maximum time to originate life was 2.5 to 11 My. Using a more conservative estimate for the flux of impacting objects before 3.8 Ga, a maximum time of 25 My was found for the same range of impactor kinetic energies. The impact model suggests that it is possible that life may have originated more than once.
Document ID
19900043560
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Oberbeck, Verne R.
(NASA Ames Research Center Moffett Field, CA, United States)
Fogleman, Guy
(SETI Institute Moffett Field, CA, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Publication Information
Publication: Origins of Life and Evolution of the Biosphere
Volume: 19
Issue: 6, 19
ISSN: 0169-6149
Subject Category
Life Sciences (General)
Accession Number
90A30615
Distribution Limits
Public
Copyright
Other

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