Astronaut Heidemarie Stefanyshyn-Piper suffered an astronaut blunder after she mistakenly let go of her tool bag in space after a grease gun inside of her backpack-sized bag exploded.

"Uh, we have a lost tool," Stefanyshyn-Piper said as she watched the bag float away.

It seems that the grease gun began to leak inside of the bag, which inadvertently lubricated everything inside the bag.  The bag floated away as she tried to manage the mess, but the lack of gravity proved too much.

NASA astronauts will now track the bag for the next few days, watching to make sure it doesn't impact the ISS.

Despite the incident, the spacewalkers were able to clean and lubricate the joints on a solar array located on the outside of the ISS.  NASA scientists believe a lack of lubrication was the initial reason the joint stopped working, and hope they don't have to worry about finding metal shavings on any future spacewalks.  

As researchers on Earth become increasingly concerned about the amount of space junk floating aimlessly in orbit, astronauts working aboard the ISS have lost items during spacewalks.

In July 2006 during a spacewalk, astronauts Michael Fossum and Piers Sellers were testing different ways to repair the ISS and managed to lose a 14-inch putty knife.  Several months later, astronaut Joe Tanner mistakenly sent a bolt, spring and washer into space.  

Space junk could potentially impact the ISS or a shuttle going to or departing the ISS, which could be catastrophic, space experts repeatedly warn.

Astronauts on the ISS were recently forced to fire boosters on the European Space Agency's Automated Transfer Vehicle to help lower the orbit of the ISS one mile.