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From: cpf@batcomputer.TN.CORNELL.EDU (Courtenay Footman)
Newsgroups: sci.space
Subject: Re: Martian meteors on earth
Message-ID: <1220@batcomputer.TN.CORNELL.EDU>
Date: Wed, 15-Oct-86 22:14:50 EDT
Article-I.D.: batcompu.1220
Posted: Wed Oct 15 22:14:50 1986
Date-Received: Thu, 16-Oct-86 05:58:07 EDT
References: <686@scicom.UUCP>
Reply-To: cpf@batcomputer.UUCP (Courtenay Footman)
Organization: LNS, Cornell University, Ithaca NY
Lines: 36
Keywords: martian, meteors

In article <686@scicom.UUCP> galyen@scicom.UUCP (Robert Galyen) writes:
>
>
>In the Saturday (Oct. 11) Rocky Mountain News there is a article about 8
>meteors found in India, Egypt, France, Anarctica, Nigeria, Brazil, and
>United States that are suppose to have originated from Mars, based on
>similar geologic characteristic and chemical composition.  Speculation is
>the meteors were blasted into space when a large asteriod or comet impacted
>the martian surface resulting in generation of jets of hot gases which could
>have propeled meter sized objects into space, exceeding the martian escape
>velocity of 11,300 mph.  
>
>The article doesn't mention a size for the impacting object other than
>asteriod or comet, is there a size definition for these planetary inter-
>lopers?  Is there any way of determining the minimum size required of an
>impacting object?  Also, it seems that the proximity of the moon, the low 
>lunar gravity, and some of the larger impact events would have combined to
>send lunar 'litho' grams to earth.
>
See the latest Science for an article about these eight objects.  It gives the
result of a detailed (2-D) calculation of how these objects could have
been thrown off Mars.  Basically it involves a ~1 Km meteorite traveling
at ~7.5 Km/sec that impacts at an angle of 20 to 60 degrees;  among
other things, a large, dense, fast jet of gas forms that can (relatively)
gently push things off the surface.   That `gently' is important; there is 
more than enough energy to blast something off Mars, but accelerating 
it without vaporizing it is tricky.

Also, many meteorites are from the moon;  I don't remember the exact numbers,
but I think that there are more of them from the moon than Mars.

-- 
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Courtenay Footman		ARPA:	cpf@lnsvax.tn.cornell.edu
Lab. of Nuclear Studies		Usenet:	cornell!lnsvax!cpf
Cornell University		Bitnet: cpf%lnsvax.tn.cornell.edu@WISCVM.BITNET