On the Cover: This enhanced false color mosaic of Landsat images covers a portion of the eastern Sahara. The Uweinat Mountain, 40 kilometers across, is the largest topographic prominence, and causes a vast spindle-shaped, sand-free zone. The mountain rises at the borders of Egypt, Libya and Sudan. Smaller features also cause a dark, sand-free zone in their lee. Similar features have been imaged by spacecraft orbiting Mars. Farouk El-Baz
4 Detecting and Studying Extrasolar Planets: John Appleby and Arthur Vaughan describe at the technology aiding in the search for planets beyond our solar system.
8 Alien Life—Forms and Function in Fluids: James Burkelooks at life on Earth to think about life on other planets.
10 Is It Earth...or Is It Mars? Farouk El-Bazcompares the planets with satellite images.