PLEASE NOTE:


*
Date sent:        Thu, 16 Oct 1997 08:44:41 -0400 (EDT)
From:             Benny J Peiser <B.J.PEISER@livjm.ac.uk
Subject:          NEO News (10/15/97)
To:               cambridge-conference@livjm.ac.uk
Priority:         NORMAL

from: David Morrison <dmorrison@mail.arc.nasa.gov
 

NEO News (10/15/97)

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MORE ON 19TH CENTURY CATASTROPHISM

Duncan Steel writes that last week's issue of New Scientist carried a
letter from him pointing out Lord Byron's suggestion in 1822 of the
possibility (indeed, necessity) of diverting any comet found to be on
a collision course with the Earth:

"Who knows whether, when a comet shall approach this globe to destroy it, as
it often has been and will be destroyed, men will not tear rocks from their
foundations by means of steam, and hurl mountains, as the giants are said to
have done, against the flaming mass? - And then we shall have traditions of
Titans again, and of wars with Heaven."

This is on page 185 in "Journal of the Conversations of Lord Byron: Noted
during a Residence with his Lordship at Pisa, In the Years 1821 and 1822" by
"Thomas Medwin, Esq., of the 24th Light Dragoons," printed for Henry
Colburn, New Burlington Street, London, in 1824 (but with several later
editions, usually labelled "Medwin's 'Conversations of Lord Byron'", in
which the pagination would be different).

Steel continues:  As a matter of fact the idea of cometary impacts was a
recurrent theme in Byron's published writing, reflecting his belief that
there had been many impact catastrophes in which previous inhabitants of the
Earth had been wiped out.  Byron viewed homo sapiens as being perhaps only
temporarily in the ascendent (unless we manage to develop a defense system
such as that he suggests in the quote above).  Indeed on the page cited
above he is also quoted as asking: "We are presently in the infancy of
science. Do you imagine that, in former stages of this planet, wiser
creatures than ourselves did not exist?"
 

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THE EL PASO BOLLIDE OF OCTOBER 9

A bright bollide was widely seen in West Texas on October 9.  A news report
at http://www.msnbc.com/local/ktsm/9198.asp suggests the El Paso authorities
identified an impact site about an acre in size some 27 miles east of El
Paso and 20 miles north of a border patrol checkpoint.  Sonic booms and
shaking of buildings were reported over thousands of square miles.  There
has been a lot of web traffic on this report, and several people have
suggested that the object may have had an energy of hundreds of kilotons, a
diameter of tens of meters, and may have done substantial damage.  Irate
questions were asked why the military did not detect this incoming object
and provide warning.

If fact, this appears to be an example, all too familiar, of exaggerated
media reporting being further amplified on the web.  As a result, a very
bright but otherwise innocuous fireball is turned in to a major impact
event.

An observer at McDonald Observatory is reported to have estimated the
magnitude of the object at about 1/100 the brightness of the Sun.
Recalling that the Wesern Pacific bollide of 1 February 1994 was "as bright
as the Sun" and had an estimated energy of roughly 100 kilotons, I suggested
that the Texas bollide might have an energy nearer 1 kiloton and hence a
pre-impact diameter of a meter or two.  Victor Noto now sends a report of
preliminary findings from a Los Alamos National Labs New Release: "The
object's infrasonic signature was equivalent to the explosive yield of about
500 tons of TNT," ReVelle said. "That means the object was somewhere around
one half to three-quarters of a meter in diameter."  Meanwhile, later media
reports suggest that the "impact site" was an unrelated brushfire.

A meter-size object with an energy of a kiloton strikes the Earth's
atmosphere every day or two.  While it is possible that this fireball
produced a meteorite, more likely it did not.  In any case the hazard of
such impacts is extremely small.  We need to keep a perspective on such
events and resist the temptation to exaggerate them for the media.

David Morrison



CCCMENU CCC for 1997

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