Martian Sand Grains on Penny

This close-up image shows Martian sand grains that settled on the penny that serves as a calibration target on NASA's Curiosity rover. This image, taken cropped from a larger scene by the Mars Hand Lens Imager, is 200 percent larger than the original, PIA16131. The larger grain under Abraham Lincoln's ear is about 0.008 inches (0.2 millimeters) across; the one under the first 9 in "1909" is about 0.004 inches (0.1 millimeters) across. Geologists classify grains of this size as fine sand and very fine sand.

Image credit: NASA/JPL-Caltech/MSSS