We have a tag-along

Trojan asteroid tags along on Earth's orbit: The asteroid in the Earth's orbit around the sun has been hiding from view, mostly overhead during daylight, study finds

Turns out the moon's not the Earth's only traveling companion. Space scientists have discovered an asteroid that's been following our fair planet for thousands of years, at least — and there may be many more where it came from, according to a recent study.

This one is at too eccentric an orbit to visit properly, but if others are found, they may be candidates for a NASA probe or mission.