Q: What odds would you give that there is currently extraterrestrial life in the solar system?

Chyba: 50-50. The only way to find out is to go and look.

Farmer: If I had to place a bet, I would say the likelihood that primitive microbial life has developed on Mars or Europa is about 50:50. This is less a reflection of sound scientific arguments than the fact that I am, by nature, optimistic!

Jakosky: I wouldn't give odds, as it is not relevant to do so. Rather, I would argue that the above issues (life's robust nature) make it plausible that life could exist on Mars, Europa, or elsewhere, and it justifies a search for life there. Finding out whether life actually does exist there becomes, in some sense, a test of our theories about life on Earth, and an indicator of whether or not life (at least, microbial life) is likely to be widespread throughout the universe.

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