Other astronomers soon counted some two dozen pieces of comet Shoemaker-Levy 9 and worked out its strange history and fate. In July 1992, it seemed, the comet had swung so close to Jupiter that the giant’s massive gravity had torn it apart. Now the remnants, some of them hundreds of feet wide, were destined to collide with Jupiter in July 1994. When the time came, most of the world’s astronomers were watching.
The impacts took place on Jupiter’s far side, out of sight of Earth, but the blows sent superheated gas billowing far above the atmosphere. The largest unleashed shock waves that roiled an area at least three times the width of Earth. “It was pretty awesome,” Carolyn says. The Shoemakers basked in the glow of their discovery. Then tragedy struck. In 1997 they were in a head-on car crash in the Australian outback. Gene died at the scene. An ounce of his ashes traveled to the moon with NASA’s Lunar Prospector spacecraft.
Carolyn scattered the rest at Meteor Crater.
If the Shoemakers’ namesake or the monster that annihilated the dinosaurs were bearing down on us, there would be little we could do. For every planet killer, however, there are thousands of smaller asteroids and comets—up to a mile or so across—that could conceivably be deflected. First we’d have to see them coming.
In 1998 the U.S. Congress ordered NASA to identify at least 90 percent of the largest asteroids and comets in the inner solar system—objects six-tenths of a mile or more in diameter. To date, telescopes have pinpointed more than 700 out of an estimated population of 1,000. In 2005 Congress got more ambitious, directing the space agency to track down the far more numerous asteroids 460 feet or more in diameter—still big enough to take out a city or state.
A new telescope is about to begin scanning the sky for these dim, elusive objects. From a peak on Maui, the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS, will scrutinize the night sky with a 1.4-billion-pixel camera that produces images so detailed a single one, if printed, would cover half a basketball court. Computers will scan the data, flagging statistical curiosities that astronomers can check the old-fashioned way, by taking a look. The Maui telescope is just a prototype; ultimately, Pan-STARRS will include an array of four cameras. “We’ll have catalogs of all the things that go bump in the night,” says Ken Chambers of the University of Hawaii, including perhaps 10,000 potentially hazardous asteroids.