`` We drove over it . 2013 : The Opportunity Team 's tires slid off a piece of rock . That piece is the ' nut rock ' that looks like a doughnut . The rock has high levels of manganese and sulfur .
2013 : The Opportunity Team 's tires slid off a piece of rock . That piece is the ' nut rock ' that looks like a doughnut . The rock has high levels of manganese and sulfur .