The bargain $425 million mission will seek to answer how Mars formed. With Curiosity, Spirit and Opportunity, Phoenix and others, scientists now know a lot about the Martian surface, but not much is known about the planet's insides. Still no one is sure whether the planet has a molten core, for instance. Opportunity made some measurements this spring that will help, but InSight will get lots more answers. It's practically a carbon copy of the Phoenix lander, which successfully photographed the Martian snow. Like almost every other Mars lander, InSight is solar-powered. Learn more about it in the video at the bottom.