Hey, Chicken Little! The Upper Atmosphere Research Satellite (UARS) satellite that NASA said would fall to the Earth some time this weekend entered the Earth's atmosphere last night or early this morning. NASA isn't sure when exactly...or where the six tons of debris are! Here's the update:

NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty.

Scientists didn't think that debris would hit anyone. Even NASA Tweeted, "The chances that you (yes, I mean YOU) will be hit by a piece of the #UARS satellite today are one in several trillion. Very unlikely," and later answered the question " Is it better for space junk to crash down to earth, such as the UARS satellite or continue orbiting?" with this explanation, "Space junk falls to Earth every day; big stuff like #UARS about 1/yr. When fuel runs out, there's nowhere to go but down."

ABC News reports, "NASA said some 26 chunks of the old satellite -- which is roughly the size of a bus -- are likely to survive the descent, and fall at hundreds of miles per hour over an area of some 500 square miles." The NY Times notes, "There are no known instances of anyone being injured by falling space debris (though in 1997, a woman in Oklahoma was brushed by a piece of mesh from a Delta 2 rocket booster that did her no harm). When the space shuttle Columbia disintegrated during re-entry in 2003, the seven astronauts aboard died, but no one on the ground was hurt as 42.5 tons of debris showered down from West Texas to southwest Louisiana."