In September 2002, astronomers noticed something odd: An object about 60 feet long was orbiting Earth. It must have arrived recently, but it didn’t resemble any recently launched spacecraft. It might have been an asteroid … but it appeared, spookily, to bear titanium dioxide paint. Was it an alien ship?

The object disappeared again in June 2003, so officially we’re still baffled. But the best guess is that it’s an old stage of Apollo 12 that somehow wandered away from Earth in 1971, circled the sun about 30 times, and came home to visit. If that’s true then it might come back again in 2032—we can visit it on our rocket scooters.