This object entered earth orbit in june 2002. When first discovered, it was first thought it could be Earth's third natural satellite. (Yes, we have two! See footnote 1.) A captured asteroid, perhaps?
The potential for mining and scientific research was enormous! One small problem- after careful observation and investigation of images, it was found the objects colour was consistent with white titanium dioxide paint- the same kind used on Apollo (Saturn IV B) booster rockets...
It was determined that this object was in fact the third stage booster rocket from Apollo 12, launched on the 14th November 1969, and this stage seperated on the 18th.
It probably first went into earth orbit, but quickly passed through the Earth's L1 point, and went into orbit around the sun. It has now been recaptured, but as the xyz file shows, it will be lost to solar orbit again in May 2003.
1. Earth's second natural satellite (not really a moon though) is called Cruithne and was discovered in 1986. You can also download this object's ssc file from this site.