Asteroid Comet Impact Hazards - Florida International University

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Report on the Tunguska International Workshop Bologna, Italy, July 14-17, 1996 range of densities. He said we should be looking for an object with a density around 2 g/cm3 . Comets seem to be about 1g, stony asteroids about 3 g, and irons about 7g. E.M. Shoemaker (US Geological Survey) also avoided the semantic trap of the comet/asteroid dichotomy by saying, "Anyone who says he knows what a comet is, is kidding himself." He then turned to his main subject of the frequency of impact events similar in energy to the Tunguska object and suggested that we can expect a Tunguskalike event about every 300 to 150 years. Other papers addressed the subject of the physical processes induced by the motion of comet nuclei in a planetary atmosphere (V. Fortov, Russian Academy of Science); how a comet nucleus explodes in a planetary atmosphere (V. Kondaurov, RAS); and the hazard from small impacts and what can be done about them (A.W. Harris, JPL). In addition to the presentations listed, there were many more, most of which would greatly interest anyone curious about the nature of the Tunguska object. Hardly a word was said about the bizarre suggestions that the Tunguska object may have been a mini black hole, a piece of antimatter, or an errant 2,000-year-old Japanese nuclear spacecraft returning home but missed the runway. A tight focus was kept on the object being either a comet or stony asteroid, as Vasilyev summarized: "Can the Tunguska explosion be explained as a result of destruction of lumps of comet ice or a meteoroid similar to carbonaceous chondrites? Who is right--Sekanina and Chyba denying such a possibility, or Bronshten, Boyarkina, Korobeynikov, Grigorian, and other investigators seeking to prove the cometary origin hypothesis? If the former are right, then it becomes imperative to revise a large number of calculations dealing with the mechanism of destruction of the Tunguska object that have been published since 1963. It is also necessary to re-explain the isotopic and elemental anomalies found at the epicenter of the area of destruction, and to re-interpret the atmospheric optical anomalies of the summer of 1908." Vasilyev's list of things to be re-explained and re-interpreted--if we accept the stony asteroid hypothesis-goes on and makes for fascinating reading. As he said, an awful lot of very suggestive data have been revealed by Russian investigators over the years, data that the stony asteroid modelists have not been aware of or have chosen to ignore. What is the future of Tunguska investigations, and what research is begging for investigators? Here is Vasilyev's wish list: 1. Establish a Tunguska homepage on the Internet and keep it current. 2. Although a Tunguska "preserve" has been established by the Russian government, there is no money to support it. What happens to the wealth of archival materials that for years have been haphazardly stored in cardboard boxes and under the beds of investigators? 3. Research projects looking for investigators from the international community of scientists: A. Cut and store peat samples from Tunguska for future analysis. B. Genetic abnormalities in plants and people on the chromosomal level. Abnormalities first detected in people in 1910: Rh factor abnormalities. Botanists to collect seeds and pollen during the growing http://www.galisteo.com/tunguska/docs/bologna96.html (3 of 4)12/5/2005 4:31:08 PM
Report on the Tunguska International Workshop Bologna, Italy, July 14-17, 1996 season--end of June, July, August. C. There are rare metals concentrations in the 1908 layer of peat and soil. What is it? How did it get there? Requires not only field work, but laboratory work to analyze samples chemically. D. Magnetic disturbances of the blast were recorded at Irkutsk. They are very similar to those caused by nuclear test explosions detonated by the English on the island of Palmira at an altitude of from 10 to 12 kilometers. How do we explain those similarities? In the Tunguska epicenter there is a change in magnetic orientation of soil particles. There are only two laboratories in Russia capable of analyzing soil samples for magnetic anomalies."We need assistance," says Vasilyev. The 1996 Bologna meeting was an important one and is bound to keep the Tunguska Event alive and well for some time to come. Back to top For comments and suggestions about this site, please send e-mail to rgal@aol.com http://www.galisteo.com/tunguska/docs/bologna96.html (4 of 4)12/5/2005 4:31:08 PM
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Asteroid Comet Impact Hazards - Florida International University

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