Mars exploration has turned out to be much more difficult than NASA had optimistically hoped in the wake of Pathfinder’s stunning success in 1997. Since then the failure of the two 1998 Mars Surveyors has changed everything. But even with these equally stunning failures, the program was headed for a radical revision, as over the past year it’s become clear that NASA’s hopes to return the first samples from Mars in 2008 for a total cost of about $400 million were wildly optimistic.