Titanian Dunes

Caption NASA:"This pair of images, taken by the Cassini spacecraft radar mapper on two different Titan passes on Dec. 11, 2006 (T21 left) and Oct. 29, 2005 (T8 right), represent two different views of a field of dunes located near 9,4° South Latitude by 290° West Longitude.
The images were taken in synthetic aperture mode and have a resolution of approximately 500 mt(1.640 feet). North is toward the top of both images and each image is approx. 400 Km (250 miles) long by 275 Km (about 170 miles) wide.
The images are different only because the radar instrument illuminated the dunes from different directions. Acting somewhat like a flash camera, the radar sends out microwave pulses and makes an image from the pulses after they are reflected back. Imagine that both the camera and the flash come from the left in the left image and from the top in the right image.
Most obvious differences are seen in the large bright feature at the center of both images. At left, its left edge is brighter, emphasizing the more steep slopes there. Farther left, the dunes are more clearly defined in the right image as their faces are caught by the illumination. However, since the dunes are visible in both images, it is likely that the materials making up the dark and light stripes are also somehow different. More detailed studies of how materials on Titan reflect and scatter at different angles are giving us clues about what different materials might be present in this cold and distant world".