If—as seems ever more likely—we render this planet uninhabitable, we now have a prospective new home. Scientists have found a planet that is the best candidate yet to be Earth-like and capable of supporting life. It's called Gliese 581d, and the weather is lovely. It just takes 3,000 lifetimes to get there.
Scientists have long eyed the system of Gliese 581 as a possible source of habitable exoplanets because it had three planets in the "habitable zone"—the area at the distance from the star where it's neither too hot nor too cold. The first planet, Gliese 581e, actually was too cold. And Gliese 581g turned out to not even exist at all. But Gliese 581d, according to new measurements, is just right.
So, welcome to our future home. There are no days on Gliese 581d; one side is perpetually light and one side is perpetually dark. People thought this would mean that the night side would be perpetually frozen. But a new study by the Laboratoire de Météorologie Dynamique at the Institute Pierre Simon Laplace found that because of the local star's red light that penetrates deep into the heavy carbon atmosphere, the planet regulates heat quite well. Downside: It will always be a sort of red-hued dusk. And gravity is twice as strong, meaning it won't be too pleasant to walk around. But at least we'll be able to live there. The problem, as with most things in space, is the distance. At 20 light years away, it would take 300,000 years to get there.
There is still a chance that all these measurements are wrong, or that the planet is rendered uninhabitable by too much helium in the atmosphere. Also, given that we're basing these measurements on light from 20 years ago, the people of Gliese 581d could be destroying their environment as we speak. By the time we arrive, we might find a planet in worse shape than Earth is.
[Image, just of the red moon, not of Gliese 581d, but you get the idea: Flickr user +gAbY+]