Pib's Comments on "Three Minutes to Impact"


On February 9, 1997, the Discovery Channel here in the States aired a two-hour program entitled "Three Minutes to Impact" on the threat posed by cosmic impacts. I have only watched the program once so I may have missed some crucial tidbits.

The program began with Duncan Steel tagged as "Doomsday Astronomer," followed closely by Gene Shoemaker labelled as hailing from "Lowell Obeservatory" (does it have to go on a diet?), followed by David Morrison posed against a background tableau of gaming tables (in Los Vegas, I assume). Based upon these scenes I had the sinking feeling that watching the following two hours might prove to be an ordeal. Fortunately, I was wrong. The rest of the program was much better than the first few minutes seemed to indicate.

Gene Shoemaker and his wife Carolyn were shown scouring the Australian outback for potential impact structures. They spend up to three months a year doing this. Gene Shoemaker has a close working relationship with the Space Shuttle program. He suggests possible impact sites for radar imaging based upon his ground work.

Hildebrand and Sharpton squared off on the size of the Chicxulub crater. Recent work by investigators from Imperial College, London to settle the question of the crater size was featured. (These researchers were shown but I do not believe they were named. I assume they were Morgan and Warner.) Their preliminary results indicate a crater diameter of 150 miles, the average of the sizes previously proposed by Sharpton and Hildebrand. I was surprised that the pioneering role played by Penfield in identifying the Chicxulub crater received no mention.

Mike Baillie and Michael Rampino discussed the possible impact origin of the atmospheric veil of 536 A.D. This segment briefly discussed the importance of tree rings and ice cores in reconstructing climatic interventions. Also offered was the suggestion that the "dragons" of mythology -- for example, in the King Arthur legends -- might be allegorical references to comets and meteors.

David Levy's obvious enthusiasm was infectious as he talked about the impact of Shoemaker-Levy 9 on Jupiter. The roles played by Brian Marsden, Paul Chodas, and Jim Scotti received mention. Images of the impacts on Jupiter, taken with several different instruments, were presented. Unfortunately, no one commented on what the Jovian impacts told us about Jupiter's structure.

Michael Rampino elaborated on the relationship between impact events and mass extinctions. He suggested that the Permian killer impactor's crater might be found near the Falkland Islands.

Ramiro de la Reza discussed his investigation of the "Brazilian Tunguska" of 1930. This included an interview with an eyewitness to the event. I will be very interested to learn what his upcoming ground expedition to the possible impact site reveals.

Shin Yabushita and Duncan Steel offered a sobering analysis of the dangers posed by impact-generated tsunamis.

Duncan Steel narrated a chilling segment on the deleterious global effects which would result from the impact of a several kilometer diameter object with New York City as the bullseye.

David Morrison commented on the probabilities of death by impact. He noted that there are few professionals working in locating near-Earth objects which might threaten us. The budgetary woes of some of the few who are -- Tom Gehrels, Duncan Steel, Eleanor Hellin -- were emphasized.

I liked the graphic illustrating how pock-marked the Earth would appear if it had not developed an atmosphere. There would be twenty times more craters on the Earth than on the moon.

A few results from probes sent to Halley's comet in the mid-1980s, during its last passage through the inner solar system, were presented. Curiously, I don't believe NASA's upcoming NEAR mission was discussed at all, although Clementine II received a nod.

Several proposed methods for deflecting objects on a collision course with the Earth were highlighted with attractive animations and interviews with folks like Edward Teller. David Morrison underscored some of the holes in current defense strategies.

Statistics such as "forty-five tons of cosmic debris strikes the Earth every day," and "two hundred or so asteroids cross Earth's orbit at any given time," were stressed.

Both Nemesis and galactic oscillation were offered as possible causes of comet showers.

There was little discussion of the relationship between comets and asteroids. Coverage of the origin of asteroids was inadequate. There was no mention of coherent catastrophism, the giant comet hypothesis, or the Taurid complex. There was no mention of comet families derived from fragmentation. There was no discussion of asteroidal moons, contact binaries, rubble piles, or recent suggestions about terrestrial crater chains (other than the Henbury craters).

The Tunguska blast was ascribed to a cometary fragment, but not to the Taurid complex. The standard view of workers here in the States -- that the Tunguska impactor was a non-cometary stony body -- was not mentioned. I would have liked to see an interview with someone who had actually worked at the Tunguska site. Likewise for Sikhote Alin.

There was no mention of the effects of impact events on recent human history except for the possible 536 A.D. event. There was no discussion of damage to people or property caused by historical small-scale impacts.

The definition of punctuationalism offered -- as evolution driven by impacts -- is certainly not that proposed by its originators, Gould and Eldredge. This is likely to confuse someone not already familiar with the standard definition of punctuationalism.

Gene Shoemaker noted that without Jupiter as "protector" the Earth would have been be struck at least 100 times more frequently. I wish his comment would have been followed up with a discussion of the consequences of such an enhanced impact flux on the Earth's biosphere. I doubt that life here would have developed past the stage of simple organisms.

There was no mention of the role of comets in delivering volatiles, and possibly pre-biotic compounds, to the inner planets.

I found "Three Minutes to Impact" to be entertaining. I liked its limiting interviews only to workers actively involved in research on impacts and impact defense. I learned a couple of things I did not know about before, such as Shoemaker's connection to the Space Shuttle program, and the planned expedition to the site of the 1930 Brazilian impact.

One of the authors of "Three Minutes to Impact" was David H. Levy, co-discoverer of Comet Shoemaker-Levy 9 which collided with Jupiter in 1994. Levy received an Emmy award for this documentary.


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Last modified by pib on July 6, 2003.