Asteroid Comet Impact Hazards - Florida International University

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