[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Fossils in meteorites
___________________ Forward Header __________________________________
Author: firstname.lastname@example.org 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
++++++ TEMPEL OV SPOON ++++++
@---@ _______________ @---@
||| |\ _,,,--,,_ ,)|||
||| /,`.-'`' -, ;-;; |||
||| |,4- ) )-,_ ) /\ |||
||| '---''(_/--' (_/-' |||
"A Distorted Worldview Since 1989"