🚀 go-pugleaf

In article <1993Jan11.070745.23686@mr.med.ge.com> hinz@picard.med.ge.com (David Hinz (hinz@picard.med.ge.com)) writes:
>By what mechanism do these rocks get here?  Volcanic action & random launching?
>How do they acheive escape velocity?

Probably by complex phenomena associated with large impacts.  One of the
sticking points on declaring the SNC meteorites to be definitely Martian
has been the difficulty in explaining precisely how they got off the planet.
Getting shrapnel from a large impact off the Moon is not hard, but Mars's
escape velocity is rather high for this kind of thing.

>Why do they end up so often in 
>Antarctica?  Or are they just more  visible there? ...

This one's just a sampling effect.  Antarctica is a great place for
meteorite hunters, because any rock found sitting on the ice *must* be
a meteorite -- there's no other way it could get there.  Elsewhere, it
is hard to tell whether a random rock belongs where it's sitting or not.

In particular, if memory serves, there are a few areas of Antarctica
where ice flows just sort of terminate, gradually eroded away by wind
rather than flowing into the ocean.  A meteorite which falls on ice that
is heading that way will end up on the surface in the termination area.
This concentrates meteorites from large areas over long periods of time.

A bonus is that the Antarctic environment is very cold and virtually
sterile, preserving the meteorites in very nearly their pristine state.
-- 
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  henry@zoo.toronto.edu  utzoo!henry