NASA's Spitzer Space Telescope showing a band of dust around the bright star that strongly matches the contents-such as water ice, organics, and rock-of a comet busted apart in a collision.

Just a fortnight ago, astronomers using the Hubble space telescope identified water vapour in the atmosphere of an exoplanet, albeit a gaseous exoplanet some 150 light years away.

Kepler is the first telescope to be designed to find Earth-sized planets that orbit in the "habitable zone" where temperatures are neither too hot nor too cold for water to remain in its liquid state.