You've got the tent tied to the roof of the van, the kids strapped into the backseat, and you've hit the highway. Where's the campsite? You know it's somewhere in the state of Wyoming, but all you have to go on is a highway map and a beautiful photograph. Let's see—there's a campfire pit, some pine trees, and a nondescript mountain in the distance. Any minute now, the kids will start screaming.
The NASA scientists charged with planning Mars outings face a similar lack of information. Three orbiters have mapped the planet, and three rovers have inched over tiny patches of terrain. Yet scientists still don't have enough data to pick the ideal destinations for tomorrow's robotic or human explorers. Mars is a big place—its surface area is the same as Earth's, minus the oceans. Where are the best spots to find evidence of Martian life? Where might water be ...
