A couple of decades ago Norm Sleep (I think, could have that wrong) gave a talk at UCSB about how life could have gotten started on earth, and he talked about the asteroid bombardment, and that large ones would have made a global lava ocean. There was a late bombardment; I forget the age of that...was it 3.9 billion?

There may well be interesting stuff in Pavel's book, and maybe I would learn something, but as I said in a post on a thread below, I need to read published scentific papers on the subjects and regions I work on.

Chris