NASA's six-wheeled robot rumbled to Gediz Vallis Ridge on Mount Sharp, a mountain the rover has slowly climbed since 2014. The ridge is evidence from some 3 billion years ago, when Mars was a wet world, replete with lakes and roaring rivers. Back then, colossal debris flows hurled mud and car-sized boulders down the mountain; eons of the whistling Martian wind then chiseled away at this material, leaving the Gediz Vallis Ridge.