Those rocks suffered a gigantic impact, a long period in the vacuum of space being bombarded by radiation, then a fiery re-entry.
I don't know for sure, but wouldn't that be a pretty effective way of sterilising rock?
I don't know for sure, but wouldn't that be a pretty effective way of sterilising rock?
Bacteria surviving on the rock would need to be buried deep inside to be shielded in such a way, and eventually break out to the surface.