Europe Goes to Mars

On the Cover: The European Space Agency's <i>Mars Express</i> captured this image—a mosaic of overlapping images gathered during five separate orbits of Galle crater, also known informally as "Happy Face" crater. The impact crater is located on the eastern rim of the Argyre Planitia impact basin near 51 degrees south latitude and 329 degrees east longitude. A large stack of layered sediments forms an outcrop in the southern part of the crater (lower part of the image). Several parallel gullies, possible evidence of liquid water on the Martian surface, originate at the inner crater walls of the southern rim. The friendly "face" was first pointed out in images taken by NASA's <i>Viking 1</i> orbiter in 1976.