Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally. They dominate the Grand Erg Oriental of the Algerian Sahara, as depicted in this image acquired October 27, 2012. It covers an area of 37 x 43 km, and is located at 29.8 degrees north latitude, 7.9 degrees east longitude.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
Extremely heavy rains fell at the end of February 2012 in the northern Algerian province of El Tarf, near the Tunisian border. The rainfall total was the greatest recorded in the last 30 years. The Seybouse River overflowed its banks, submerging adjacent villages. Overflow from the Bougous, Mexa and Cheffia dams added to the misery. In this image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft, acquired March 1, 2012, vegetation is shown in red and water is depicted as black to turquoise, depending on how much sediment it contains. The image is located at 36.7 degrees north latitude and 8.3 degrees east longitude. It covers an area of 22 by 37.2 miles (34 by 60 kilometers).
With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on Terra. The instrument was built by Japan's Ministry of Economy, Trade and Industry.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
