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.
To answer this question, the team looks at four broad requirements. The first is a platform or substrate on which life can gain a toehold. It could be rock or ice. Either provides a stable platform, can corral chemical elements that can serve as food, and provides a surface on which chemical reactions can take place.
An atmosphere and a planetary magnetic field would be big pluses as shields from excessive radiation from space. Plate tectonics also would be a big plus because it recycles elements on the surface and helps stabilize a planet's climate.