Mars Rover Panorama Shows Sweeping 'Marathon Valley' (Photo)

An epic Mars panorama shows the snaking valley that NASA's long-lived Opportunity rover has been exploring for the last year — and will likely soon leave behind. The newly released photo — a composite of many images Opportunity captured in April and May — depicts Marathon Valley, a feature that cuts across the western rim of the 14-mile-wide (22 kilometers) Endeavour Crater. Opportunity arrived in the valley in July 2015 to hunt for clay minerals, signs of which