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From: mmt@dciem.UUCP (Martin Taylor)
Newsgroups: net.astro,net.space
Subject: Re: Death Star?
Message-ID: <768@dciem.UUCP>
Date: Wed, 7-Mar-84 14:51:10 EST
Article-I.D.: dciem.768
Posted: Wed Mar  7 14:51:10 1984
Date-Received: Wed, 7-Mar-84 15:59:39 EST
References: <543@ihuxb.UUCP>
Organization: D.C.I.E.M., Toronto, Canada
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There was a recent article in Science referring to the periodicity of mass
extinctions, and enquiring into the possibility of periodic large impacts.
They searched for iridium anomalies (and other exotic elements or isotopes
associated with meteorites) in sediments at extinction boundaries, but
found none except at the well-known Cretaceous boundary.  This doesn't
deny the possibility of periodic massive impacts, but neither does it
lend much support to the idea.  (Sorry, I didn't keep the issue, and I
don't have the reference, but it was within the last 6 weeks or so.)
-- 

Martin Taylor
{allegra,linus,ihnp4,uw-beaver,floyd,ubc-vision}!utzoo!dciem!mmt