The Bad Astronomer writes "The extrasolar planet GJ 1214b was discovered in 2009 orbiting a nearby (40 light year distant) red dwarf star. The planet was quickly found to have a thick atmosphere, but it wasn't known at the time if the composition was water vapor or a hazy shroud of particulates. New Hubble observations confirm the atmosphere of the exoplanet is rich in water, comprising up to 50% of the atmosphere's mass (PDF). At 230 degrees Celsius, this means the planet is shrouded in steam."

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