Scientists have so far detected at least 550 planets outside the solar system – and another 2,000-plus await confirmation. But how to pick out the ones that may be Earth-like havens for life? Here's what one team looks for in assessing any planet's potential habitability and its similarity to Earth's properties.
The White House's 2015 budget request includes $15 million for the development of a mission to Europa, a Jovian moon thought to harbor liquid water.
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