Number 180 (Story #2), May 27, 1994 by Phillip F. Schewe and Ben Stein|
WHEN THE FRAGMENTS OF COMET SHOEMAKER-LEVY strike Jupiter one after the other in mid-July, what will we see? A panel of scientists, addressing this subject at the Spring Meeting of the American Geophysical Union in Baltimore this week, agreed that a lot depended on the size of the bang. Hubble Space Telescope scientist Harold Weaver said that his best estimate of the size of the larger comet chunks was 1-2 km. Mordecai-Mark Mac Low of the University of Chicago has performed computer simulations which show that the fireball of hot gas (not unlike that of a nuclear bomb) resulting from the breakup of comet fragments in Jupiter's atmosphere will rise above the cloud tops. A 1-km fragment may well trigger an explosion equivalent to a million nuclear bombs; the fireball for such an event, Mac Low believes, might be visible above the limb of Jupiter even though the actual impact site will not yet have rotated into view. Drake Deming of NASA Goddard discussed the sound waves (accounting for as much as 30% of the impact energy) that will move through Jupiter's atmosphere following each impact. Such waves would eventually refract upwards into Jupiter's stratosphere where they might be imaged by infrared detectors on Earth. The Galileo spacecraft, on its way to Jupiter, is actually in a position to directly observe the impact sites, although the nature of its detectors and the speed at which data can be downloaded precludes full images. According to Torrance Johnson of JPL, careful information from other telescopes about the exact timing of the impacts may help the retrieval of selected Galileo measurements---such as an overall brightening of Jupiter due to the impacts---in the days following the event.