NEO News

From: B.J.PEISER@livjm.ac.uk <B.J.PEISER@livjm.ac.uk>
To: cambridge-conference@livjm.ac.uk <cambridge-conference@livjm.ac.uk>
Date: 16. oktober 1997 9:44
Subject: NEO News (10/15/97)
From: David Morrison <dmorrison@mail.arc.nasa.gov>

NEO News (10/15/97)

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?"

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