That's the debris left over from malfunctioning satellites, rocket stages and even lost equipment from space walks.
It continues to float in orbit, littering space with debris.
And it's a growing concern.
Brian Bremner wrote about this in an article for Bloomberg Businessweek and he joins us now.
On how the film “Gravity” portrays space junk:
"'Gravity'’s commercial success has brought to light a problem that’s been around for a few decades and that’s the accumulation of space debris in low orbit and the dangers that it poses to existing satellites and manned missions."
On how much junk is in space:
"A lot. If you consider that the space age really began in 1957 when the Russians launched Sputnick, since then mankind has put up roughly 7000 different space craft of all sorts and satellites up into low orbit, medium orbit, space. Along the way there have been collisions and rocket motor [parts] and metal fragments have collected and we’ve reached a critical mass where it’s posing some dangers."
On why space junk is a concern now:
"We are now getting to the point where there’s so much stuff up there that debris is colliding against other debris and forming even more debris, this kind of cascading effect, that scientists at NASA are getting concerned about and we may be getting to the point, although there’s disagreement among engineers about this, we could see more collisions up in space that could be a problem."
On possible solutions for space junk:
"The Europeans are coming up with an approach and may try it later in the decade and put a robot on top of an airbus … and it would have a robotic claw that would go and catch big pieces of debris.
Space is a common resource but no one is ultimately responsible for cleaning it up."
On the danger space junk could pose to people on the ground:
There was a case in November, a European science satellite—it was a monster it was 1.2 tons … and ran out of fuel in low orbit and then came back into the atmosphere—it was tracked—it didn’t pose any immediate danger and kind of disintegrated over the southern pacific. That was a good scenario; they knew about it and tracked it.