This image shows the topography of two of the hemispheres of Mars. The image was seen on the cover of Science magazine in May of 1999. The most prominant features in this image are: 1) The massive Hellas impact basin (upper-left) in the Southern Hemisphere which is nearly six miles (nine kilometers) deep and 1,300 miles (2,100 kilometers) across. The basin is surrounded by a ring of material that rises 1.25 miles (about two kilometers) above the surroundings and stretches out to 2,500 miles (4,000 kilometers) from the basin center. 2) The lower-right image shows the Tharsis province that contains Tharsis Montes (Ascraeus, Pavonis, and Arsia), and the Valles Marineris canyon system and related outflow channels.