The notion of panspermia – the transferral of viable organisms between planets, and even between star systems, seems to be getting a bit more attention these days. […]

There is no doubt that planetary surface material is continually being shipped around between rocky planets and moons in our solar system. Ejected by high energy asteroid or comet impacts, chunks of stuff follow a range of orbital trajectories that result in both eventual return to their origins or transferral to the surfaces of other worlds. Increasing evidence suggests that a variety of (typically microbial) organisms could be carried along, surviving both the extremes of pressure and acceleration, as well as exposure to thousands to millions of years of interplanetary space. They need not do this in stasis, tucked well inside the interstices of rock and ice it’s not inconceivable that microbes could be passengers in the natural equivalent of the generation ships of science fiction.

It means that there is a real possibility for life to both cross-infect, and even to be ‘seeded’ from planet or moon to planet or moon. […] Enthusiasts for panspermia go further, and have been known to invoke these mechanisms for galaxy-wide dispersal of life – taking one rare occurrence of life and spreading it across the stars. […]

There is a factor about large-scale panspermia that to my knowledge is rarely considered, and that is natural selection. […] The sequence of events involved in panspermia will weed out all but the toughest or most serendipitously suited organisms. So, let’s suppose that galactic panspermia has really been going on for the past ten billion years or so – what do we end up with?

{ Scientific American | Continue reading }

photo { Adam Kremer }

space | October 17th, 2012