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Distant world looks too ripe for life

Though in the habitable zone, newly discovered planet probably not habitable

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.”

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