The Mars rovers, Spirit and Opportunity, are heading into two new and very different adventures in their pursuit of further geological evidence that water once flowed on the planet. Spirit is speeding like a clipper ship toward the now not-so-distant Columbia Hills from its landing site at Gusev crater. Its twin, Opportunity, is surveying the rim along the football stadium-sized Endurance crater on the Meridiani plain for a potentially perilous pathway into the crater to investigate a huge, cantilevered bedrock outcrop.