Astronomers peering at Mars in the 17th and 18th centuries saw signs of life everywhere. Seas! Continents! Canals that carried water to Martian farms! You spot none of these features as your spaceship deploys its parachutes for touchdown on this cold desert world—but then you never expected to. Mars has been the subject of many myths; you intend to separate science fact from science fiction as you step on the surface of the red planet.
For starters, the red planet isn’t even totally red! Browns, tans, golds, and flecks of green pop out as you scan the rocky, dusty, dune-laden landscape. Mars only looks red from far away because of rusting iron minerals in the rocks and soil. The soil blows into the air (occasionally in planetwide dust storms) to give the atmosphere a bloody tint. Water may have flowed on Mars long ago, in ancient seas and riverbeds that early astronomers confused for canals. That was back when the atmosphere was thicker. Now, the air here (mostly carbon dioxide) is too wispy to support water or hold much heat. If you took off your spacesuit and stood on the equator at high noon, your toes would feel toasty but your face would be freezing! The good news is summer here lasts for six months. The bad news: So does winter!