With the launch of NASA’s new Kepler spacecraft, the chances of discovering Earth-sized planets in Earth-like orbits around distant stars have increased. However, the real question for astrobiologists is, are these worlds habitable? Can we find an Earth-like planet with an Earth-like atmosphere? Answering such questions may prove to be very difficult.

Future missions like the James Webb Space Telescope (now scheduled for launch in 2013) may help astronomers characterize the atmospheres of distant planets, helping astrobiologists identify a true Earth twin beyond our solar system.