DOH!,
Hum, well spotted.
That idea seems to be at the forefront of current thinking.
But i suppose this does not mean that it is the ONLY route to creating long (self replicating) molecule chains...
There were crystalline structures (er, the holes) that were observed by the rovers...and we know that there is loads of sulphur and hydrogen (in water) there.
The very early earth would have resembled the moon IO ,according to recent studies, and that doesn`t seem that nice a place to grow-up in...
Plus, it could be that once life has arisen SOMEWHERE in our galaxy, the time scale to colonise/infect the ENTIRE MILKY-WAY may be as little as a million years...
The method of transportation would be on rocks blasted away from planetary impacts and on tiny dust particles trailing behind the planet (and lost in space)...
This link may be of interest to others , about meteorite ALH84001 : )
http://www.users.muohio.edu/mcmahosp/ (the mars meteorite from the Allan Hills ice field in the Antarctic )
And if we find nothing...
The real puzzle maybe is, why life is it not there already...