For the first time, astronomers predicted when and where an asteroid would strike Earth—and recovered pieces of the rock to prove it. By studying the orbit of the asteroid and examining its remains, researchers hope to reconstruct more details about conditions in the early solar system. The work also serves as a dress rehearsal for efforts to discover larger, potentially deadly incoming asteroids before they hit.
Astronomers with the Catalina Sky Survey in Arizona spotted a car-size object headed our way on October 5, 2008, when it was about as far away as the moon. After quickly determining that the rock was too small to cause damage, scientists at the Minor Planet Center at the Smithsonian Astrophysical Observatory calculated its trajectory. Less than a day later the asteroid—now classified as a meteor—exploded 23 miles above Sudan’s Nubian Desert, exactly as was expected.
The story did not end there, however. Meteor astronomer Peter Jenniskens of the SETI Institute in California suspected that chunks of the rock might have survived the fiery descent. He enlisted a team of local Sudanese students to comb the desert of northeastern Sudan and managed to recover almost 300 fragments totaling 10 pounds. In a March paper published in the journal Nature, Jenniskens reported that the rocks were part of a porous asteroid that formed rapidly during Earth’s infancy, some 4.5 billion years ago. The fragility of the asteroid explains why it exploded so high up in Earth’s atmosphere. “By looking at this trail of bread crumbs,” Jenniskens says, “we can go back in time and see how the asteroid evolved.”