The European Space Agency says one of its research satellites, the Gravity field and Ocean Circulation Explorer (GOCE), re-entered the Earth's atmosphere early Monday on an orbit that passed over Siberia, the western Pacific Ocean, the eastern Indian Ocean and Antarctica.
The 1,100-kilogram (2,425-pound) satellite disintegrated in the atmosphere but about 25 percent of it - about 600 pounds of "space junk" - slammed into the Atlantic between Antarctica and South America, a few hundred kilometers (miles) from the Falkland Islands, ESA said. It caused no known damage.
This time it splashed down in the Atlantic Ocean - but what about next time? And how often does this occur?
Overall, some 6,600 satellites have been launched, 3,600 of which remain in space. Only about 1,000 are still operational, according to ESA. Not all are still intact, and the U.S. Space Surveillance Network tracks some 23,000 space objects.
A lot of junk comes down unnoticed, said ESA Space Debris Office deputy head Holger Krag. Statistically, he said, "roughly every week you have a re-entry like GOCE."
Over the course of the year, about 110 to 165 tons of space junk re-enters Earth's atmosphere each year, according to Heiner Klinkrad, the head of ESA's Space Debris Office. In 56 years of spaceflight, a total of 16,500 tons of human-made space objects have re-entered the atmosphere.
Most of this space junk travels at about 17,400 mph shortly before re-entry at about 75 miles above the earth, according to ESA. It starts to slow down and heat up in the dense atmosphere. In the last 10 minutes, it hits a traveling speed roughly equal to that of a Formula One racing car -between 125 mph to 190 mph.
Despite the amount of space junk falling each year, there have been no known human injuries or significant property damage caused by space junk, according to ESA. Unlike meteorites, which hurl into the Earth as solid chunks traveling about three times faster, space junk typically falls as fragments and is distributed over a fallout zone up to 600 miles long. Krag says fragments from a satellite came down in 2011 over the Netherlands, Germany and the Czech Republic but no pieces were ever found.
One of the best-known instances of falling space junk is NASA's Skylab space station, which re-entered in 1979. About 82 tons hit the Earth - some of it in Australia and the rest falling into the Indian Ocean. Fragments of Russia's Mir space station weighing about 149 tons came down in 2001 in a controlled dive into the Pacific Ocean. More recently, in 2011, NASA's UARS satellite crashed into the Pacific and Germany's ROSAT satellite landed in the Bay of Bengal. None caused any damage.
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