Reseeding of early earth by impacts of returning ejecta during the late heavy bombardment

Details Reseeding of early earth by impacts of returning ejecta during the late heavy bombardment Reseeding of early earth by impacts of returning ejecta during the late heavy bombardment

Mar 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003icar..162...38w&link_type=abstract

Icarus, Volume 162, Issue 1, p. 38-46.

Biology

19

Earth, Exobiology, Impact Processes, Prebiotic Environments

Scientific paper

Mounting attention has focused on interplanetary transfer of microorganisms (panspermia), particularly in reference to exchange between Mars and Earth. In most cases, however, such exchange requires millions of years, over which time the transported microorganisms must remain viable. During a large impact on Earth, however, previous work , Icarus 160, 183-196) has shown that substantial amounts of material return to the planet of origin over a much shorter period of time (< 5000 years), considerably mitigating the challenges to the survival of a living organism. Conservatively evaluating experiments performed [by others] on Bacillus subtilis and Deinococcus radiodurans to constrain biological survival under impact conditions, we estimate that if the Earth were hit by a sterilizing impactor ~ 300 km in diameter, with a relative velocity of 30 km s-1 (such as may have occurred during the Late Heavy Bombardment), an initial cell population in the ejecta of order 103-105 cells kg-1 would in most cases be sufficient for a single modern organism to survive and return to an again-clement planet 3000-5000 years later. Although little can be said about the characteristics or distribution of ancient life, our calculations suggest that impact reseeding is a possible means by which life, if present, could have survived the Late Heavy Bombardment.

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