"It scares me," said Jack Hills, an astronomer at New Mexico's Los Alamos National Laboratory. "It really does." He and the rest of the world had good reason to be worried. Astronomer Brian Marsden, at the Harvard-Smithsonian Center for Astrophysics had just announced that a newly discovered asteroid 1.6 km wide was headed for Earth and might pass as close as 48,000km in the year 2028. "The chance of an actual collision is small," Marsden reported, "but not entirely out of the question."
An actual collision? With an asteroid of that size? It sounded like the stuff of science fiction and grade-B movies. But front-page stories and TV newscasts around the world soon made clear that the possibility of a direct hit and a global catastrophe well within the lifetime of most people on Earth today was all too real.
Then suddenly, the danger was gone. Barely a day later, new data and new calculations showed that the asteroid, dubbed 1997 XF11, presented no threat at all. It would miss Earth by 1 million Km - closer than any previously observed asteroid of that size but a comfortable distance. Still, the incident focused attention once and for all on the largely ignored danger that asteroids and comets pose to life on Earth.
XF11 was discovered last Dec. 6 by astronomer Jim Scotti, a member of the University of Arizona's Spacewatch group, which scans the skies for undiscovered comets and asteroids. Using a 77-year-old telescope equipped with an electronic camera, he had recorded three sets of images. The digitized images, fed into a computer programmed to look for objects moving against the background of fixed stars, revealed an asteroid that Scotti, in an e-mail to Marsden, described as standing out "like a sore thumb."
