Sometime in the next few weeks, pieces of a defunct  satellite will rain down on an unlucky patch of Earth.

Precisely where and when the  will hit home are not yet known, though the U.S. government will have a better picture of the so-called "debris footprint"—expected to be roughly 500 miles (805 kilometers) long—as the satellite's date with destiny draws near.The doomed spacecraft, known as the Upper Atmosphere Research Satellite (UARS), was carried aloft by the  Discovery in 1991 to study .

When the satellite was switched off in 2005, it became another piece of potentially hazardous space junk, so NASA nudged it toward Earth, aiming for a downward trajectory that would cause the craft to burn up in the atmosphere.Now the satellite itself will become a type of experiment: Can an uncontrolled 6.3-ton object plummet out of orbit without hitting anybody?

At a press briefing Friday, NASA said there's generally little danger of death by space debris. Since the dawn of the  some five decades ago, no human has been killed or even hurt by an artificial object falling from the heavens.Many space objects experience a carefully controlled demise. Russia's Mir space station, for example, was steered into a remote patch of ocean in 2001. (Related: 

But other pieces—old rocket segments jettisoned in orbit and abandoned spacecraft—fall toward Earth unguided. Last year one object a day, on average, made an unshepherded dive into the atmosphere, said NASA's Nick Johnson.

To date nearly 6,000 tons of human-made material have survived the fiery journey through our atmosphere, according to the , a space-research center.Here are some of the notable objects that have made surprise return trips to Earth:

Sphere of Influence

In March a hiker in northwestern spotted a spherical object, still warm to the touch, sitting in a crater. The hiker called military aerospace officials but was told to instead call the county sheriff, according to an orbital-debris . Eventually the hiker reached the NASA office that tracks space debris. The tank, from a Russian Zenit-3 rocket launched in January, is one of the few such space objects to be recovered in the United States.

Brush With Space Junk

A woman taking a late-night walk in  in January 1997 saw a streak of light in the sky, then felt something brush her shoulder. It turned out to be part of a U.S. Delta II rocket launched in 1996—the only space debris known to have hit someone, according to the Aerospace Corporation. The woman was unhurt—and lucky. A 580-pound (260-kilogram) fuel tank from the same rocket slammed to the ground in Texas around the same time, narrowly missing an occupied farmhouse, NASA reports.

Nuclear Waste

In January 1978 the Soviet surveillance satellite Kosmos 954 crashed in northern , scattering radioactive material from the spacecraft's nuclear power generator over thousands of square miles, the Canadian government said. A frantic campaign dubbed  was mounted to find the radioactive material, but only 0.1 percent of the dangerous debris was ever recovered.

Space Station Shower

When the Salyut-7 space station began trailing lower in its orbit, Soviet engineers tried to send it into a controlled tumble into the Atlantic Ocean. But their efforts failed, and the 88,000-pound (39,916-kilogram) station—one of the largest human-made objects to reenter the atmosphere—showered metal fragments on a city in  where residents observed glowing trails in the sky. No one was hurt, according to the Aerospace Corporation.

Beached Rocket

In 2000 beachcombers stumbled upon a mysterious object that had washed ashore near Corpus Christi,  The finder wanted to turn the object—the pointed nose of an Ariane 5 rocket that had just launched—into a hot tub. "We convinced him … that was not an option," NASA's Johnson said.