This set of images from NASA's Cassini spacecraft shows Saturn's moon Titan glowing in the dark. Titan was behind Saturn at the time, in eclipse from the sun. The image on the left is a calibrated, but unprocessed image from Cassini's imaging camera. The image on the right was processed to exclude reflected light off Saturn, and it is clear that even where Titan did not receive any Saturnshine, it is still emitting light. Some light appears to be emanating from high in the atmosphere (noted by the outer dashed line at about 625 miles [1,000 kilometers] in altitude). But more surprisingly, most of it is diffusing up from lower down in the moon's haze, from about 190 miles (300km) above the surface. //Credit: NASA/JPL-Caltech/SSI