When John Wesley Powell and his nine men pushed their four boats out into the roaring Colorado in 1869, they had no idea what lay downriver. They set out with the knowledge that they might not return—and several did not. As I reflect on the last decade's adventure of designing, building, testing, launching, and operating two complex and hardy robotic space vehicles on Mars, I cannot help but wonder if we were just as naive when we started out. Our lives were not on the line, of course, but we certainly ended up risking our health, marriages, family relationships, friendships, to some degree our scientific careers, and sometimes, it seemed, our sanity.

Spirit and Opportunity were not the first missions to land on Mars, rove its surface, or transmit images of its ruddy alien landscape. The two Viking landers (1976-1982; 1976-1980) and the Mars Pathfinder and its Sojourner microrover (1997) beamed back tens of thousands of images that revealed Mars’ surface as rocky, dusty, and yet strangely familiar. The difference between the views taken by the earlier missions and Spirit and Opportunity is that between “acquiring images” and “taking photographs.” The former is a technical, science-driven, and resource-limited activity. Every space mission—whether human or robotic—carries a camera to pass images of alien worlds to those back home. It is not easy to take these pictures or to send them home: Spacecraft and their instruments are complex, sometimes finicky to operate. There is often little time to take pictures. Even scarcer, usually, is the bandwidth necessary to transmit good quality pictures to Earth.

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