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N.J. Woolf (Steward Obs.)
The presence of life on Earth could be the result of such a rare accident, so that life far from Earth would be exceedingly rare. The issue arises because the simplest known life forms are exceedingly complex, the apparent result of a long line of chemical and biological evolution. We know that life was relatively abundant on Earth not long after the last ocean-destroying collision occurred here. But this alone does not tell us whether or not in the development of life there was some extremely improbable step or steps. Whether life here was the result of such a fluke or flukes is susceptible to two lines of study, one observational, the other experimental. In the experimental method, one attempts to create very simple life forms. But it is by no means certain that human experimental ability is as good as nature's. The observational approach has three current facets, looking for microbial life elsewhere in the solar system, looking for chemical tracers of life in other planetary systems and looking for the communications of extra-terrestrial intelligences. All three are discussed at this meeting by Chyba, Beichman and Tarter. The discovery of life elsewhere in the solar system does not exclude a fluke -- if panspermia works within the solar system, we could all be Martians, Europans etc. in origin, and the fluke might have occurred there. If panspermia works between different planetary systems, then at best we are looking to see whether life exists with both forms of handedness, which would demonstrate that life developed at least twice, and such a test would require an interstellar vehicle. The study of chemical tracers and communications are searches designed against false positives. This paper explores the implications that would be associated with positive results from observations.