Intruder from outer space

On 3 September 2002, astronomer Bill Yeung discovered a faint, 16th magnitude object that was orbiting Earth.1 Initial excitement about this apparent asteroid, designated J002E3, centred on the remote possibility that it might, one day. impact Earth. As more data on its orbit was gathered, analysis showed that it could not have been in Earth’s vicinity for long and had probably been in a heliocentric orbit before being captured by Earth. Additionally, spectroscopic studies revealed that its surface colour was consistent with titanium oxide, the pigment in white paint. It was no asteroid.

Projecting the orbit ОҐ. Г002ЕЗ around the Sun backwards in time showed that it had previously been in the Earth-Moon vicinity in 1971, around the time of the Apollo 14 mission. However, since all of the components of that mission had been accounted for. it could not have come from Alan Shepard’s flight. Suspicion shifted to the Apollo 12 S-IVB.

After Richard Gordon had completed his TD&E exercise, the two Apollo 12 spacecraft. Intrepid and Yankee Clipper, continued on their path to the Moon in November 1969. NASA intended that Apollo 12’s S-IVB should go the same way as the previous Moon-bound third stages by having its residual propulsion slowr it dowm sufficiently to pass the Moon’s trailing limb and be slung into heliocentric orbit. Unfortunately, a guidance error by mission control resulted in a burn that lasted too long and the stage was slowed more than intended. It therefore passed too far from the Moon to achieve a proper slingshot and instead entered a large Earth orbit from which, owing to a later encounter with the Moon, it subsequently escaped. As far as anyone can tell, it was this S-IVB that had returned for Bill Yeung to catch in his telescope that September night.