This rock, informally named "Tisdale 2," was the first rock the NASA's Mars Rover Opportunity examined in detail on the rim of Endeavour crater. It has textures and composition unlike any rock the rover examined during its first 90 months on Mars. Its characteristics are consistent with the rock being a breccia -- a type of rock fusing together broken fragments of older rocks. Tisdale 2 is about 12 inches (30 centimeters) tall.
Photo credit: NASA/JPL-Caltech/Cornell/Arizona State University
Note: A number of other photos have been released with regard to Tisdale 2; see PIA14745: Locations of Microscopic Imager Observations on 'Tisdale 2', PIA14746: Magnified View of Texture on Part of "Tisdale 2" Rock, PIA14747: Elevated Zinc and Bromine in Rock on Endeavour Rim, PIA14748: Approaching 'Tisdale 2' Rock on Rim of Endeavour Crater, Sol 2690, and PIA14749: Opportunity at Work Examining 'Tisdale 2,' Sol 2695.