Nasa Satellite where it crashed

The abandoned 6-ton Upper Atmosphere Research Satellite (UARS) satellite entered the earth's atmosphere early this morning but where it crashed remains unknown according to NASA.

In an update posted on NASA's website, the "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."

Officials said it entered the atmosphere somewhere over the Pacific Ocean but the "precise re-entry time and location are not yet known with certainty."

On Friday, officials predicted the satelllite would be passing over Canada, Africa and Australia, and vast areas of the Pacific, Atlantic and Indian oceans.

The Upper Atmosphere Research Satellite (UARS) is deployed from the Space Shuttle Discovery in this Sept. 14, 1991 file photo in space.

Bill Ailor, principal engineer at the Aerospace Corp., studies incoming space junk for the Air Force. He said pieces of other satellites have come crashing down into villages, farms and random datelines around the planet.

"I actually think a lot of this kind stuff comes down and nobody knows what it is and just thinks it's junk and ignores it," Ailor told ABC News.

Ailor and his colleagues study satellite components in a lab to figure out what will burn up and what will become a potential threat -- just like the pieces of the UARS satellite.

But according to Nicholas Johnson, NASA's chief orbital debris scientist, any one person's chances of getting hit by debris are tiny -- something like 1 in 21 trillion. The chances that of the 7 billion people on Earth, one of them, somewhere, could be hit are more like 1 in 3,200.