Jupiter's Inferno

The initial, sketchy reports began filtering in by E-mail late Saturday afternoon. First a Spanish observatory announced that it had spotted a plume of gas billowing up from the edge of Jupiter. Then a group of observers in Chile confirmed the sighting, and so did another team based at the South Pole. But although the first of the 21 fragments of Comet Shoemaker-Levy 9 hit the giant planet shortly after 4 p.m. Eastern time, astronomers at the Space Telescope Science Institute in Baltimore, Maryland, had to wait for images to be beamed down from the orbiting Hubble telescope. Finally, at about 8, the first pictures came up on the video screen -- and there, right at Jupiter's edge, was a bright splotch of light. "Somebody tell me that isn't one of Jupiter's moons," said an anxious Heidi Hammel, a planetary scientist from M.I.T.

It was no moon. Despite scientists' sober warnings that the Great Comet Crash of 1994 might be an uneventful dud, the first chunk plowed into Jupiter's atmosphere with the force of perhaps 10 million hydrogen bombs, lofting a mushroom cloud of hot gas nearly 1,000 miles out into space and leaving a dark scar on the planet's familiar, brightly colored clouds. The assembled astronomers looked at the video screen for a second in silent disbelief -- then began cheering and toasting one another with swigs from champagne bottles. Said Hammel: "This is the kind of stuff I've been dreaming about."

Then she grabbed a bottle and ran upstairs to tell three visitors who had a special stake in the Hubble results: the people who had discovered the comet. Carolyn and Eugene Shoemaker are a husband-and-wife scientific duo who spend their evenings scanning the skies for heavenly intruders; David Levy, an amateur astronomer, often helps them. When the partners found Shoemaker-Levy 9 in 1993, they knew it was unusual, and further observation revealed that it was not one comet but at least 21 fragments, remnants of a single object that had been torn apart a year earlier by Jupiter's gravity -- and that all would crash into the massive planet between July 16 and July 22 in the most violent event in the recorded history of the solar system.

Astronomers couldn't agree, though, on how big the pieces were, and thus how explosive the impacts would actually be. Just hours before the pictures came down, Levy had tried to downplay expectations. "Even if we see nothing spectacular," he argued, "this is still a scientifically important event." But when Hammel had brought the word -- and the champagne -- Levy and the Shoemakers could barely contain themselves. Said a beaming Eugene Shoemaker: "This is just the best possible news. And remember, this isn't even the biggest piece."

In fact, it was on the small side, and the bigger chunks may pack up to 25 times the energy of the first. From what the experts could see Saturday evening and Sunday morning, they were confidently predicting plenty of fireworks before the last piece hits Jupiter early Friday. They were also forecasting a flood of major scientific results. The full story of Shoemaker- Levy 9's demise won't be known for a month or more, until all the reports come in from satellites and observatories, and scientists process them.