A bit of the Apollo 12 rocket from 1969 is still floating around out in space. It orbits the sun – but every thirty or forty years it comes back to orbit the Earth for a while.
Apollo 12 was the second manned mission to the Moon. They went to the Moon in part to do some lunar garbage collection, but they also left some space junk behind.
The Saturn V rocket, still the most powerful launch system in human history, was the brawn behind the Apollo lunar missions. The third stage of this rocket, designated S-IVB, pushed the astronauts and their spacecraft out of Earth orbit and on their way to the Moon (the so-called “trans-lunar injection”). Its task completed, the empty stage detached and pushed itself out of the way of the spacecraft.
In the early Apollo missions (8, 9, 10, and 11) the S-IVB floated off into a safe orbit around the sun. In the later Apollo missions (13, 14, 15, 16, and 17) the S-IVB deliberately crashed into the Moon – and they are in fact the heaviest human-made objects on the lunar surface. But the S-IVB of Apollo 12 apparently did something different.
Fast forward to 2002. An astronomer named Bill Yeung spotted what looked like an asteroid with a very strange orbit: around the Earth. This is strange because the Moon is the only large natural object orbiting our planet. Further investigations suggested that this asteroid was not actually a natural object at all. Instead, it was our lost rocket stage.
Apollo 12’s S-IVB was supposed to be in an orbit around the sun, like the third stages that came before it. The current theory, though, is that it did not have enough force to properly escape from the Earth. Instead, it orbits the sun only most of the time. Every thirty or forty years it gets close enough to the Earth to drop into a series of irregular loops around our planet. Then it shoots back out into the cosmos for another few decades.
This floating space junk left Earth again in 2003. It will probably come back for another visit in 2045 or so.