Red ball in the corner pocket.

Could be a big collision next month.

An asteroid similar to the one that flattened forests in Siberia in 1908 could plow into Mars next month, scientists said Thursday. Researchers attached to NASA's Near-Earth Object Program, who sometimes jokingly call themselves the Solar System Defense Team, have been tracking the asteroid since its discovery in late November. The scientists, at the Jet Propulsion Laboratory in La Cañada Flintridge, put the chances that it will hit the Red Planet on Jan. 30 at about 1 in 75.

A 1-in-75 shot is "wildly unusual," said Steve Chesley, an astronomer with the Near-Earth Object office, which routinely tracks about 5,000 objects in Earth's neighborhood. "We're used to dealing with odds like one-in-a-million," Chesley said. "Something with a one-in-a-hundred chance makes us sit up straight in our chairs."

The asteroid, designated 2007 WD5, is about 160 feet across, which puts it in the range of the space rock that exploded over Siberia. That explosion, the largest impact event in recent history, felled 80 million trees over 830 square miles. The Tunguska object broke up in midair, but the Martian atmosphere is so thin that an asteroid would probably plummet to the surface, digging a crater half a mile wide, Chesley said.

The asteroid is behind the moon right now, so they won't be able to get a more accurate reading of its trajectory for another couple of weeks.