NASA says that in the more than 50 years of the space age, with more than 17,000 man-made pieces of debris reentering the Earth's atmosphere, no one has ever been hurt by falling space junk — that we know of.

Maybe a solitary African hunter deep in the bush got flattened by an errant booster fragment and we just never heard about it. A 563-pound fuel tank did hit within 50 yards of a Texas farmhouse in 1997, but close doesn't count.

The Earth is a big place and 75 percent of it is covered by water, NASA likes to say in explaining why we don't have to worry about a defunct 7-ton U.S. research satellite hovering 155 to 174 miles up just waiting for the moment to take its final plunge.

The Upper Atmosphere Research Satellite was deployed from the shuttle Discovery in 1991 and decommissioned in 2005. Now, in 2011, one of the planet's unluckier years, it has chosen to return home.

NASA says it could fall later this month. Or maybe sometime in October. It could land somewhere between Juneau, Alaska, and just north of South America. A Russian publication says Moscow is in the "zone of risk." So you might want to factor those into your travel plans.

And the whole 7 tons of it isn't going to hit. Most of that will burn up in the atmosphere, but 1,200 pounds of metal will probably survive long enough to crash.

NASA says, with a verisimilitude of accuracy that only arouses suspicion, that the chances of anyone being hit by a piece of the satellite are only one in 3,200.

Nonetheless, for the next seven weeks or so, you might want to look up in the air before you step outside.

Dale McFeatters writes for the Scripps Howard News Service.

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