Anyone spot a refrigerator-sized tank of ammonia recently? It could be the largest-ever piece of astronaut litter chucked by hand from the International Space Station.

Astronaut Clayton Anderson tossed the coolant tank during a July 23, 2007 spacewalk after upgrades to the space station made it obsolete. The Early Ammonia Servicer (EAS) tank had served as a reservoir for the station in case its cooling system leaked.

The 1,400-pounds (635 kilograms) of debris was expected to enter Earth’s atmosphere yesterday or last night, reported. No word yet on whether it’s made impact.

"This has got a very low likelihood that anybody will be impacted by it," Mike Suffredini, NASA's space station program manager, told the Web site. "But still, it is a large object and pieces will enter and we just need to be cautious."

Up to 15 pieces of the tank as heavy as 40 pounds (17.5 kilograms) could land somewhere on Earth. The report doesn’t specify where they might make impact, but with two-thirds of the planet water, ocean landings are a possibility.

"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.       

Image of International Space Station by NASA