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Question: What first interested you about the search for alien life? 

Paul Davies:  I suppose my interest in looking for life elsewhere in the universe really dates back to my teens.  What teenager doesn’t look up at the sky at night and think am I alone in the universe?  Well most people get over it, but I never did and though I made a career more in physics and cosmology than astrobiology I’ve always had a soft spot for the subject of life because it does seem so mysterious.  To a physicist life looks nothing short of a miracle.  It’s just amazing what living things can do and so that sense of mystery, that sense of how did it all begin has always been there in the background and then in the 1990s I began to take a more active part, began to study the prospects that life could spread from Mars to Earth or maybe Earth to Mars and that maybe life began on Mars and came to Earth, and that idea seemed to have a lot of traction and is now accepted as very plausible, and so I was asked to help create the Australian Center for Astrobiology.  I was living at that time in Australia and we set this thing up in Sydney and I worked there for some years before moving to Arizona.

Question: How much credence has the theory that life began on Mars gained? 

Paul Davies:  Well I first suggested the idea in the early 1990s that life could have come from Mars to Earth inside rocks blasted off the red planet by comet and asteroid impacts.  I think a lot of people felt that this was a pretty crackpot notion, but it became clear during the 1990s that not only that there is a large traffic of material exchanged between Mars and Earth, but that microbes are hardy enough if protected by the rock, cocooned inside, to survive the harsh conditions of outer space for a long time, many millions of years, and the evidence both theoretical and experimental has firmed up and I think many people now realize that if you get life on either Mars or Earth you’ll get it on both planets from this splashing phenomenon.  Now the case for it beginning on Mars is not very strong.  Mars is a smaller planet, so it cooled quicker, so it was ready for life sooner.  Conditions there were more congenial for life to get going, but as we don’t know how life ever got going this is a bit of a leap in the dark, so we certainly can’t say that it definitely started on Mars, but it seems very plausible that it did.  On Mars seems as good a place as Earth for life to get started.

Question: Is this theory still controversial, and how could it be verified? 

Paul Davies:  I think astrobiologists are comfortable with the idea that it could have started on Mars and come here.  As I’ve said the evidence is not compelling, but to really clinch this we would of course need to either go to Mars and find life there and discover it is the same life as we have here on Earth or just possibly a sample return mission, which has been long awaited by the astrobiology community.  This is a spacecraft that will be sent to Mars and pick up a sort of grab bag of rocks and bring them back to Earth so they can be studied.  It’s just possible we will find traces of life in those rocks.  It’s equally possible we won’t, so it’s a bit of a long shot.  The only way to be really clear is to have some expedition to Mars and my feeling is that life on Mars today is almost certainly, if there at all, deep under the ground, maybe a kilometer or so beneath the surface, and so that is going to be hard to get at.

Recorded April 15, 2010
Interviewed by Austin Allen

More from the Big Idea for Thursday, May 13 2010


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