RE: Fossils in meteorites

["Terry Colvin" <colvint@fhu.disa.mil>]

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Author:  forteana@lists.primenet.com at smtp-fhu
Date:    11/08/96 12:50

>There's a factoid quoted in Kim Stanley Robinson's excellent 
>Martian novels (I think Red Mars) to the effect that 2% of the 
>ejecta which reach space from meteor impacts on Mars will 
>land on earth... or maybe its the other way around.
>Can anyone comment or supply further info?

This doen't quite answer you question, but this idea of interplanetary 
cross-pollination is fascinating.

The Guardian 8/8/96

>From an article by Paul Davies. Professor of Natural Philosophy at the 
University of Adelaide.

Return Ticket To Mars.

        "...It may seem baffling that chunks of Mars are found right here
on Earth. How do they get here? Every few million years Mars gets slammed 
by an asteroid or comet with enough force to blast rocks into space. You 
can see the craters clearly in satellite photos, peppering the Martian 
landscape. Over the aeons the ejected fragments become strewn around the 
solar system. Some inevitably get swept up by other planets as they orbit 
the Sun. It has been estimated that 500kg of Martian material strikes the 
Earth every year. The same process is bound to happen in reverse: big 
impacts with Earth eject debris into space, some of which will reach Mars. 
So it seems rocky material is continually being exchanged between planets.

        "During the first billion years of their 4.5 billion-year history,
the planets would have been subjected to much more intense cosmic 
bombardment. Rocks and boulders must have travelled in profusion between 
Earth and Mars.
        The significance of this discovery for life on Mars is obvious. If
Earth's rocks harbour microorganisms, then material displaced into space by 
impacts could convey live microbes to the Red Planet, whereupon they may 
emerge and colonise their new home. Cocooned within a rock, a microbe would 
be shielded from the ultra violet and cosmic radiation of outer space. In 
spore-like form, it might remain viable almost indefinitely. To reach Mars 
alive, microbes must survive their projection from Earth and the heat and 
shock of entry into the Martian atmosphere. Mathematical modelling by Jay 
Mellosh of the University of Arizona suggests that considerable quantities 
of rocks ejected by a major impact would in fact remain relatively 
unscathed. Moreover a reasonable fraction of rocks that strike the Martian 
atmosphere at a glancing angle would slow and explode, spilling their 
microbial cargo gently to the ground. Today any space-faring bugs would 
encounter harsh and probably lethal conditions on Mars. But in the past, 
when conditions were more favourable, they might have felt very much at 
home."

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