LOS ANGELES While North America appears to be off the hook, scientists are scrambling to pinpoint exactly where a dead NASA satellite will fall to Earth.
The bus-sized satellite is expected to break into more than 100 pieces as it plunges through the atmosphere today.
CBS News correspondent Bill Whitaker reports it will be a fiery end to the old satellite when it bursts back into Earth's atmosphere, which, computer models suggest, is most likely to happen somewhere over the South Pacific. But not even NASA scientists can say for sure.
Three quarters of the Earth's surface is water, so most likely, nobody will even see it.
Ted Molczan of Toronto, who tracks satellites as a hobby, says most sightings occur by chance because the re-entry path can't be predicted early enough to alert people.
In all of his years of monitoring, Molczan says he has seen only one tumble back to Earth the 2004 return of a Russian communications satellite.
He says it looked like a brilliant star with a long glowing tail.
The best guess so far is that the 20-year-old Upper Atmosphere Research Satellite will hit this afternoon or early evening, Eastern time.
The latest calculations indicate it won't be over North America at that time.
Until yesterday, every continent but Antarctica was a potential target.
Peter Brown of the University of Ontario has said the satellite's trajectory has it landing anywhere between the globe's 57th parallel in the north and the 57th parallel in the south.
Launched in 1991 to study the ozone layer, the satellite was decommissioned by NASA in 2005, then steered into lower orbit to speed up its demise, reports Whitaker. Most of the satellite will burn up on reentry, but some 24 metal chunks - some weighing as much as 300 pounds - could hit the Earth.
Man-made space debris falls to Earth all the time. The odds a piece of this satellite will hit any one person on the planet are miniscule; just 1 in 21 trillion.
"It's a very remote possibility," says Bill Ailor, director of the Aerospace Corporation, tells CBS News. "Since we've been putting things into space, we've only had one person brushed on the shoulder by a lightweight piece of debris, and that's the only one we've known that's been touched by a piece of re-entering debris."
Unlike a meteor that burns almost instantly upon reentry, the satellite could burn for several minutes, creating a colorful light show with a long glowing tail -- if it happens where anyone can even see it.