NASA flight engineer Clayton Anderson—perched at the end of a long robot arm—detached a 1,400-pound (635-kilogram) refrigeration unit from the International Space Station and tossed it overboard as space junk.

The debris will spiral 210 miles (338 kilometers) down to Earth over the next 300 days or so, NASA officials reported. Parts of the unit will burn up upon re-entry into the atmosphere, but some fragments will find their way back to the surface.

Anderson and fellow astronauts unlimbered the ammonia coolant tank after an upgrade to the station's refrigeration system made the spare unnecessary.

NASA typically ferries its junk back to Earth on the space shuttle. But with only a dozen or so missions planned to the space station before the shuttle program ends in 2010, there was no room left to bring the tank back.

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