Astronomers have discovered a planet that can sustain liquid water, the prerequisite for life as we understand it. Named Gliese 581 C, the new planet orbits a red dwarf star in what's called the "Goldilocks zone"—not so close that water melts, and not so far that it freezes.
Whether life exists there remains a mystery; Gilese is 20 light years away. But the planet, which is 50% bigger than earth, could be a target for future space missions searching for extraterrestrial life, astronomer Xavier Delfosse points out. "On the treasure map of the universe, one would be tempted to mark this planet with an X, Delfosse said.