Stellar astronomer and TED Senior Fellow Lucianne Walkowicz works on NASA's Kepler mission, searching for places in the universe that could support life. So it's worth a listen when she asks us to think carefully about Mars. In this short talk, she suggests that we stop dreaming of Mars as a place that we'll eventually move to when we've messed up Earth, and to start thinking of planetary exploration and preservation of the Earth as two sides of the same goal. As she says, "The more you look for planets like Earth, the more you appreciate our own planet."