Six astronauts aboard the International Space Station were forced to scramble into escape capsules, due to the threat of space debris from a Russian rocket. (Associated Press/NASA/Paolo Nespoli)

A discarded chunk of a Russian rocket missed the International Space Station early Saturday. However, it came close enough to force six astronauts to seek shelter in escape capsules.

NASA says the space junk was barely close enough to be a threat.

Had it hit, however, the station could have been dangerous. So the astronauts — two Americans, three Russians and a Dutchman — woke early and went into two Soyuz vehicles ready to rocket back to Earth just in case.

The debris came closest at 2:38 a.m. ET. It wasn't noticed until Friday, too late to move the International Space Station out of the way.

This is the third time in 12 years that astronauts have had to seek shelter from space junk.