Caption: NASA astronaut Clayton Anderson, an Exped...A piece of space station trash the size of a refrigerator is poised to plunge through the Earth’s atmosphere late Sunday, more than a year after an astronaut tossed it overboard.

NASA and the U.S. Space Surveillance Network are tracking the object β€” a 1,400-pound (635-kilogram) tank of toxic ammonia coolant thrown from the international space station β€” to make sure it does not
endanger people on Earth. Exactly where the tank will inevitably fall
is currently unknown, though it is expected to re-enter Earth’s
atmosphere Sunday afternoon or later that evening, NASA officials said.

“This has got a very low likelihood that anybody will be impacted by it,” said Mike Suffredini, NASA’s space station program manager, in an interview. “But still, it is a large object and pieces will enter and we just need to be cautious.”

NASA astronaut Clayton Anderson threw the ammonia tank from the tip of the space station’s Canadian-built robotic arm during a July 23, 2007, spacewalk. He tossed away an unneeded video camera stand overboard as well, but that 212-pound (96-kilogram) item burned up harmlessly in the atmosphere early this year, Suffredini said.

NASA expects up to 15 pieces of the tank to survive the searing hot temperatures of re-entry, ranging in size from about 1.4 ounces (40 grams) to nearly 40 pounds (17.5 kilograms).

If they reach all the way to land, the largest pieces could slam into the Earth’s surface at about 100 mph (161 kilometers per hour). But a splashdown at sea is also possible, as the planet is two-thirds ocean.

“If anybody found a piece of anything on the ground Monday morning, I would hope they wouldn’t get too close to it,” Suffredini said. [via]