By Jupiter! Comet Crashes Dazzle and Delight

Article excerpt

This week, humans watched as two worlds collided. More than 20 kilometer-size shards of a comet, most likely born in the frigid abyss beyond Pluto, crashed into the solar system's largest planet.

Jupiter took a bruisin' as the fragments of Comet Shoemaker-Levy 9 plowed one by one into the far side of the gas giant's southern hemisphere, collectively depositing the energy equivalent of some 40 million megatons of TNT.

Observers on Earth and spacecraft orbiting our planet couldn't see the actual impacts. But the fireworks recorded by myriad telescopes -- some even before the crash sites rotated into view -- exceeded the expectations of astronomers, who had worried that the highly publicized, 6-day event might prove a fizzle -- another Comet Kohoutek.

Within the first few hours, such concerns proved groundless. Astronomer Heidi B. Hammel from the Massachusetts Institute of Technology raced into the auditorium of the Space Telescope Science Institute (STSI) in Baltimore waving aloft a dramatic new image. Hubble had recorded a dark pockmark created by the first fragment to strike Jupiter -- even though that fragment was one of the puniest in the lineup.

"It's not a once in a lifetime [event], it's once in a millennium," declared comet codiscoverer Eugene M. Shoemaker after taking a swig from the bottle of champagne offered by Hammel. Subsequent pictures backed his assertion.

Emerging from the holes punched in Jupiter's atmosphere by the exploding fragments, plumes of hot, dark material rose higher than 1,000 km above the planet's visible cloud tops. Hubble images showed that the plume associated with fragment G -- the seventh to strike and probably the biggest -- had spread out with in 90 minutes to cover a region in Jupiter's stratosphere equal to that of Earth's diameter.

As if nature had conspired to play a practical joke, this splotchy blemish resembles a black eye floating in the planet's upper atmosphere. Clark R. Chapman of the Planetary Science Institute in Tucson reported midweek that the brightness and relative contrast of this feature in visible light had made it the single most prominent marking on the disk of Jupiter, exceeding even the planet's Great Red Spot.

By week's end, a narrow swath girdling Jupiter's southern hemisphere displayed other bruises, many of which may take weeks or even months to fade away. …