Re: It may be hard for life to get started

From: Michael S. Lorrey (
Date: Thu Jan 11 2001 - 13:48:23 MST

John Clark wrote:
> Michael S. Lorrey <> Wrote:
> > What it means is that once you realize the late peak in bombardment that
> > occured immediately before the earliest fossil evidence,
> The earliest fossil evidence is 3.85 billion years old, the peak in bombardment
> was 4.5 billion years ago when an object the size of Mars hit the Earth forcing
> a huge cloud of debris into orbit that later coalesced into the moon. I wouldn't
> call 650 million years "immediate".

There was an article in one of the science publications this past month
of another blip in bombardment that occured immediately prior to the
oldest fossil evidence. Rather than a steady descending parabolic curve
of impact frequency, there is this bell shaped blip at the 3.9 billion
year point.

> >that it was the bombardment that eliminated any early life signs we are currently
> >able to spot,
> Perhaps a later and lesser bombardment did as you say, but if it wasn't strong enough
> to eliminate signs of water I'm not sure it would be strong enough to eliminate signs of life.

Depends. Sedimentation layers in metamorphic rock is a sign of water, as
are signs of chemical erosion of granular structures. Neither depends on
life being present. The new magnetofossil evidence actually does precede
this questionable period, so the question is not so cut and dry.

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