re: How about clay? - Not just clay...
... but what's in those dirty snowballs.
Ok, and those chrondite balls that harbor our asteroid belt. (I still favor our comets).
Clays are and can certainly harbor life or 'could have in the past'. In space, I have no doubt that a dirty snow ball has and could be harbouring the elements of life... especially if it's a comet. I can't explain it, call it a hunch, a hypothesis, but where there's dirt and iced water and it comes in contact with warmth, there could be life.
I know. Call me a lunatic. :)