As Comet Pieces Crash into Jupiter, Earth Will Watch

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When pieces of a shattered comet smash into the planet Jupiter this summer, scientists worldwide will conduct one of the largest coordinated astronomical observations in history.

In addition to scientific curiosity, there also is a fascination akin to watching someone else's house get battered by a force of nature.

"Virtually every telescope in the world will be pointed toward Jupiter in July," Lucy McFadden, a University of Maryland astronomer, said Wednesday at a National Aeronautics and Space Administration news conference.

All the major observatories in the world, along with a fleet of satellites, will focus on Jupiter as 20-some fragments of the Shoemaker-Levy 9 comet collide with the planet and release about 1 million megatons of energy.

The first impact is expected on July 16, and more fragments will slam into Jupiter, like train cars derailing one after the other, over the next week.

"This is the first time in history we've been able to predict a major impact and then prepare to observe it scientifically," said Gene Shoemaker, a U.S. Geological Survey scientist who is co-discoverer of the comet.

Just what will happen at impact is an open question. Some scientists predict that each impact will produce an explosive flash, followed shortly after by an erupting fireball. Others suggest that dust from the comet fragments will disrupt the magnet envelope surrounding the planet and cause visible changes. Chemical reactions would send clouds above the gas that cloaks Jupiter, creating wispy scars that may last for years.

Or, said Shoemaker, it could all be a dud.

Jupiter, though 11 times larger than Earth and the largest planet in the solar system, is actually mostly gas. Objects falling in could just disappear. But the speed of the comet, more than 100,000 miles per hour, is expected to release enough energy to produce at least some reaction, even in Jupiter's gas.

"The worst case would be if they all just disappear, and there is no effect," Shoemaker said. "But I will really be astonished if we don't see something."

The comet was discovered by a team led by Shoemaker that conducts a small, ongoing project searching the heavens for comets using an old 18-inch telescope at the Palomar Observatory near San Diego. …