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NASA satellite won't land in Antarctica: Expert

A six-ton NASA satellite about 35 feet long and 15 feet around is falling out of the sky.

Most of the Upper Atmosphere Research Satellite, also known as UARS, is expected to burn up in the atmosphere, but some debris could land on Earth between Thursday and Saturday.

But where will the pieces land?

Derrick Pitts, chief astronomer at the Franklin Institute, said on "The Early Show" experts still don't know exactly, but have ruled out one place: Antarctica.

When asked when scientists will have a better idea of where the wreckage will re-enter Earth's atmosphere, Pitts said, "We won't have a really good sense until we get to about six hours, maybe four hours of re-entry. The reason  is the path is very long; it depends a lot on the Earth's atmosphere and how that is going to affect it, so we still have to wait to find out."

He added, "Our chances are good, don't worry!"

"Early Show" co-anchor Erica Hill pointed out the chances of someone getting hit by the debris are one in 3,200. The chances of getting hit by lightening are, Hill noted, one in a million.

In response to those odds, Pitts said, "The way I really think about this, and I encourage people to think about it, is the Earth is covered with water, 75 percent of the Earth is covered with water, so that means that the likelihood is it will fall in an ocean someplace. If it should come down over land, most of the land area of the Earth is pretty much empty. People tend to live along the coasts, so that also reduces the possible exposure for people getting struck by something."

Where will six tons of space junk land on Earth?

In a worst-case scenario, if word comes that the satellite is going to re-enter in a populated area, Pitts said, "The first thing to think about is that most of this will completely disintegrate on re-entry. There are some pieces -- about 26 pieces could make it to the surface. And the thing that we have to be aware of is, once the call is made that this could come down over a populated area, if people stay indoors, that would be a good thing. That would minimize the kind of damage or impact on people. But, again, the chances are so slim that that would happen."

Other satellites, Hill said, will also come down in the years to come. Is there a way to control where they do?

Pitts said, "What happens with most satellites is a little bit of fuel is saved until very, very late in the mission to direct where the object is going to fall into the Earth's atmosphere. In this case, almost all of the fuel was exhausted earlier on in its life history. And the other problem is that solar activity also plays a role in helping determine when it's going to fall into the Earth's atmosphere. So solar activity heats the atmosphere, it expands, catches the satellite (and) brings it down."