What a joy and a relief that we’re back on Mars. The fourth stone from the sun has taunted us for centuries with shifting but persistent visions of nearby alien life. Finally, after several conspicuous failures, we have a conspicuous success: a six-wheeled, mini-Cooper-sized robot preparing to crawl across an ancient lake-bed, scratching and sniffing for subtle signs of past habitability. What we will do on Mars for the next few months and, with future missions, for the rest of the decade, is clear: dig in the dirt and take in the air to learn the history of landscapes far more ancient than any left on Earth. But what should we plan to do on Mars over the following decades, centuries, and millennia?