This anaglyph from NASA's Mars Exploration Rover Opportunity shows an unusual, lumpy rock informally named 'Wopmay' on the lower slopes of 'Endurance Crater.' 3D glasses are necessary to view this image.

This three-dimensional view from the navigation camera on NASA's Mars Exploration Rover Opportunity shows an unusual, lumpy rock informally named "Wopmay" on the lower slopes of "Endurance Crater." Opportunity took the frames that make up this image on the rover's 250th martian day, or sol, on Oct. 6, 2004. Later, Opportunity investigated the rock with instruments on its robotic arm.

The rock's informal name refers to Wilfrid Reid "Wop" May, a Canadian bush pilot. Scientists believe that the lumps in Wopmay, like traits of "Escher" and other rocks dotting the bottom of Endurance Crater, may be related to cracking and alteration processes, possibly caused by exposure to water. The area between intersecting sets of cracks appears to have eroded in a way that shaped the lumpy appearance. Wopmay measures approximately 1 meter (3.3 feet) across.

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