This shows a greyscale 3-mm image of the Moon, observed with the NRAO 12 Meter Telescope. The smoothly varying component of emission has been subtracted, and the result has been edge enhanced. This brings out sharper variations in radio brightness, showing many crater-like features on the surface. Note how the radio surface of the Moon appears very different from the familiar optical surface; the radiation mechanisms are quite different. The radio picture is measuring the temperature at the surface, while optically we see scattered sunlight.