You probably didn’t know that the Earth has a second ‘moon’, which orbits our planet on a crazy path called a horseshoe orbit, as can be seen in the video above.
Cruithne is tiny – about the size of the comet 67P/Churyumov-Gerasimenko, which is currently playing host to the Rosetta orbiter and the Philae lander.
Forgan says Cruithne is of more value to us than just curiosity.
So what can we learn about the solar system from Cruithne? Quite a lot. Like the many other asteroids and comets, it contains forensic evidence about how the planets were assembled. Its kooky orbit is an ideal testing ground for our understanding of how the solar system evolves under gravity…
One day, Cruithne could be a practice site for landing humans on asteroids, and perhaps even mining them for the rare-earth metals our new technologies desperately crave. Most importantly of all, Cruithne teaches us that the solar system isn’t eternal – and by extension, neither are we.
Bill Condie is a science journalist based in Adelaide, Australia.
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