This three-centimeter by three-centimeter (1.2-inch by 1.2-inch) microscopic image from the Mars Exploration Rover Opportunity's "Eagle Crater" soil survey displays a mixture of light and dark soil units at the target called "Cookies and Cream" in the "Neopolitan" area. There are several different types of clasts, or particles, held in surrounding fine-grained sands: rounded spherules, angular, irregular fragments (containing what are presumably vesicles or small cavities) and small, rounded clasts about one millimeter (.04 inch) in size.
Image credit: NASA/JPL/Cornell/USGS
