This gives context for image sizes from the Optical Microscope on the Mars Phoenix Lander. The upper left picture was taken on Mars by Phoenix and shows the microscope's sample stage exposed to accept a dust sample kicked up by the spacecraft thrusters. The other images taken on Earth show close-ups of circular substrates on which the microscopic samples. Each circular substrate target is 3 millimeters (about one-tenth of an inch) in diameter. Each image taken by the microscope covers an area 2 millimeters by 1 millimeter (0.08 inch by 0.04 inch), the size of a large grain of sand. Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University
