Theia and the Goldilocks Zone

Beyond the Earth and Moon there is a vast and empty space, visited just by a few tiny fragments of asteroids drawn inwards by the sun’s gravity, and occasionally a manmade satellite travelling out on a voyage of exploration. As voids go in space this is nothing extraordinary, the immeasurable entity of space is made up almost entirely of nothing.  But the space between Earth and our neighbouring planet Mars is different. This, at least in our terms, is prime real estate space. The region that starts a little in from the orbit of Earth to just outside the orbit of Mars is our star’s Goldilocks zone. Not too hot and not too cold, in fact just right to support life. In many ways it is a careless waste that this huge expanse has just two planets in it, and one of those, Mars, is on the very margins of habitability. But it might have been different. A leading theory about the early Earth says that 4.5 billion years ago the Earth was a slightly smaller planet than it is now, and orbiting close by was another planet, smaller still, called Theia. The theory says that Theia collided with Earth fragmenting both. When gravity reassembled the wreckage a larger Earth and our moon were formed. Theia was no more. But what if events had unfolded differently? We would live in a slightly smaller Earth, with no moon. But just out there would be another world. Perhaps instead of the Apollo moon landing, Neil Armstrong would have stepped out onto the surface of Theia. Perhaps he may have found he was not alone another world in the Goldilocks zone could have supported life of it’s own too. So perhaps it wouldn’t have been Neil Armstrong. Instead a Theian mission of beings would have landed on the Earth first.