Jupiter's Comet Encounter Stirs Astronomical Broth

COMET Shoemaker-Levy 9 is gone. But the worldwide effort to track the effect of its impact on Jupiter continues.

Some 21 comet fragments hit the giant planet between July 16 and 22. Traveling at 130,000 miles an hour, they delivered the equivalent of about 40 million megatons of TNT - or roughly 500 times the energy yield that the combined United States and Soviet nuclear arsenals represented at their peak, according to estimates reported by the Associated Press.

The information service of the European Southern Observatory in Garching, Germany, observed last week: ``There is no doubt that the impacts very effectively stir the soup'' in Jupiter's atmosphere. Astronomers are counting on this stirring to turn up molecules and initiate chemical reactions that will reveal details of the atmosphere's composition. And they hope that seismic vibrations have been created that will penetrate the planet and reveal something of its inner structure.

It will take months, perhaps years, to glean this understanding from the data still being gathered. ``Quick look'' observations, however, have found evidence of methane, sulfur, hydrogen sulfide, carbon monoxide, and a few other molecules. In spite of at least one provisional detection of water, there is little evidence of it so far. This suggests that the comet fragments may not have penetrated deeply enough to reach the layer of water that astronomers think underlies the ammonia-rich outermost part of the atmosphere. Astronomer Stephen Maran at the NASA Goddard Space Flight Center in Greenbelt, Md., says the fact that there is carbon monoxide on Jupiter shows there is oxygen there that could make water. He adds: ``We're seeing a lot of chemistry coming in. We just don't know what it means.''

Meanwhile, the European Southern Observatory (ESO), which redistributed many observers' reports and telescopic images via the electronic ``information highway,'' has noted that ``a new kind of observational astronomy has emerged'' to keep track of the impact spots on Jupiter. Professional and amateur astronomers are working as a global team whose members are interconnected by computer information networks.

Dr. Maran notes there has been another important ``social effect'' of last week's drama. The massive impacts have reinforced the need to inventory solar system objects that might hit Earth. The United States House Committee on Science, Space, and Technology has prepared legislation to authorize the National Aeronautics and Space Administration to plan a 10-year program to catalog all asteroids and comets larger than a kilometer in diameter that cross Earth's orbit.

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