A 3-D view of a digital elevation map of a sample collected by NASA's Phoenix Mars Lander's Atomic Force Microscope (AFM). The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate, which is the background plane shown in red. A Martian particle -- only one micrometer, or one millionth of a meter, across -- is held in the upper left pit. Image: NASA/JPL-Caltech/University of Arizona/University of Neuchatel/Imperial College London
