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Path: utzoo!utcsri!ubc-vision!alberta!andrew
From: andrew@alberta.UUCP (Andrew Folkins)
Newsgroups: net.astro
Subject: Re: Halley's Doomsday
Message-ID: <691@alberta.UUCP>
Date: Wed, 16-Oct-85 14:12:36 EDT
Article-I.D.: alberta.691
Posted: Wed Oct 16 14:12:36 1985
Date-Received: Wed, 16-Oct-85 15:57:16 EDT
References: <646@petrus.UUCP>
Reply-To: andrew@pembina.UUCP (Andrew Folkins)
Followup-To: net.astro
Distribution: net
Organization: U. of Alberta, Edmonton, AB
Lines: 30
Summary: 


A few months back, I became temporarily obsessed with 100 metre diameter
nickel-iron asteroids.  Calculations similar to those in <646@petrus>
revealed that these (as asteroids go quite) small pieces of rock would
produce megaton-order explosions if one was to hit the Earth. Fortunately,
most of this type of material was swept up several billion years ago, and
the current odds of an impact of this magnitude are something in the
neighbourhood of one every million years. For those of you, like Opus, 
who are deeply worried about being killed by Halley's Comet, the closest
approach is (approximate, I haven't got my Sky & Telescope here) 
about 30 million miles.

Incidentally, did you know that a 100 metre nickel-iron asteroid would
be worth several billion dollars as ore?  Assuming a density of 8 gm/cm3,
the mass of the asteroid would be approximately 24 million metric tonnes
of possibly fairly pure nickel iron.  This is the approximate equivalent
of 5% of the world's TOTAL output of steel, from just one piddling little
asteroid.  (This doesn't include the gold, platinum, etc. would could
be present as impurities).  Just think - if someone wanted to put a few
nukes to use and try to move an asteroid into Earth orbit, the expedition
could practically pay for itself.  The metal would be even more useful
if used in orbit - how much would it cost to lift that much material
from the surface of the Earth?  (Anyone for a discussion of the relative
merits of asteroids vs. lunar material for orbital construction?) 

-- 
Andrew Folkins        ...ihnp4!alberta!andrew    
 
"Any statements to the effect that this parrot is still a going concern
 are hereby considered inoperative!"