NASA's falling satellite: Where will it hit?

Sometime in the next few weeks, a six-ton satellite will fall to Earth, and it probably won't hit anyone — or so NASA hopes. The satellite, known as the Upper Atmosphere Research Satellite, or UARS, was put into orbit in 1991 to study atmospheric changes such as the effect of pollutants on the Earth's ozone layer. In 2005, UARS was decommissioned and has been slowly losing altitude ever since. Now that UARS is close to crashing, NASA has no idea where it will hit. Here's what you should know:

How big is the UARS satellite?

Roughly the size of a bus. It's 35 feet long and 15 feet wide — fairly large by space-junk standards. But most of that will burn up as the satellite passes through the Earth's atmosphere. Still, roughly 26 separate pieces are expected to remain intact, with a combined weight of about 1,100 pounds. The largest chunk could be the satellite's main body, weighing about 330 pounds — roughly the weight of a large refrigerator.

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What's the likelihood that it will hit someone?

Slim. NASA estimates there's a 1-in-3,200 chance that any piece of UARS will strike a person. Most of the time, space debris falls on unpopulated land or into the ocean, since more than two-thirds of the Earth's surface is ocean. "Things have been re-entering ever since the dawn of the Space Age; to date nobody has been injured by anything that's re-entered," says NASA official Gene Stansbery, as quoted by SkyNews.

Is NASA always so careless about space junk?

Not anymore, since space junk has become an increasing concern among the world's space agencies. Current standards require that a retired satellite have enough reserve fuel to put it into a "graveyard" orbit, or that it be brought down to Earth in a controlled manner. But when UARS was commissioned two decades ago, those standards weren't in place.

Sources: MSNBC.com, NewsDaily, SkyNews, Space.com