NASA announced several days ago, an upcoming press conference that would talk about “alien life”. This is big news. They have sent more than one mission to Mars looking for life, water and extraterrestrials. But several people, including the late Sir Fred Hoyle, have suggested that alien life was coming here, which would save a lot on expenses. The question became, how do we know it is alien?
Paul Davies, working from a suggestion from my colleague Richard Hoover, has been looking for life on our planet that does something different from all other Earth life. The argument is a bit indirect, but here’s the gist of it. If life exists on our planet by accident (standard Darwinian hypothesis) then it must be somewhat probable. That is, if it is as improbable as Hoyle calculated, 1 chance in 10^40,000, then it is so improbable as to never happen. But it must have happened (by accident, we’ve assumed) and so it must be probable, say 1 in 10^20. (This step involves two miracles, making it less robust than a one-miracle theory.) Well if it is probable, then life must be popping up all over the galaxy, wherever there’s the right conditions for it. However, many of the parameters of life appear arbitrary, like the code that connects DNA codons to protein amino acids. So it would seem that if the right conditions included lots of arsenic and no phosphorus, then naturally it would be arsenic-DNA. In addition, it should probably show other signs of extraterrestrial source, perhaps a different DNA code, and different ATP energy source, etc.