Looking back: Purgatory Dune - Sol 491

Caption NASA originale:"The wheels of NASA's MER Opportunity dug more than 10 cm (such as 4") deep into the soft, sandy material of a wind-shaped ripple in Mars' Meridiani Planum region during the Rover's 446th Sol (April 26, 2005).
Getting the Rover out of the ripple, dubbed 'Purgatory Dune', required more than 5 weeks of planning, testing and carefully monitored driving. Opportunity used its NavCam to capture this look back at the ripple during Sol 491 (June 11, 2005), a week after the Rover drove safely onto firmer ground. The ripple that became a sand trap is about 1/3rd meter (one foot) tall and 2,5 mt (8 feet) wide".