Distant world looks too ripe for life

The snazziest addition to the Kepler mission’s stable of confirmed planets is kind of a tease. A bit bigger than Earth, planet Kepler-22b orbits a sunlike star at a distance where liquid water, and therefore life, can exist.

But Kepler-22b is unlikely to be habitable.

The planet’s radius, only 2.4 times Earth’s, probably makes it too big to be life-friendly, says planetary scientist Abel Mendez at the University of Puerto Rico in Arecibo. Mendez produces the Planetary Habitability Catalog, a newly released compilation of exo-objects, each graded for habitability. He used Kepler-22b’s radius to calculate possible masses and densities. Mendez says the most optimistic habitable scenario would be if Kepler-22b were a sort of water planet, with a global ocean and some clouds. But even that is only marginally life-friendly, he notes. “I’m not optimistic,” Mendez says. “But I would love to be wrong.”