The Mars Global Surveyor, which is studying the Red Planet from orbit, has produced the first three-dimensional map of Mars.
The map shows that Mars is a world of dramatic topographic extremes -- there is about 19 miles' difference between the highest and lowest points, which is about 1A times the range of elevations found on Earth.
The Northern Hemisphere is about three miles lower on average than the Southern Hemisphere and has the smoothest surface found in the solar system. Scientists suspect it may have once contained a vast ocean.
The Southern Hemisphere (both top images) is pockmarked by giant craters, massive volcanic mountains and huge gorges. The most striking feature is the Hellas basin, most likely formed by an asteroid impact. The crater (blue area on right image) is nearly six miles deep -- deeper than any other known in the solar system. It's about 1,300 miles across and surrounded by a ring of material that stretches 2,500 miles from the center.
The vast Valles Marineris canyon (lower right of left image) slices across the Southern Hemisphere while the three Tharsis volcanoes (depicted in red and white in left image) thrust up from the surface. The Olympus Mons volcano (upper left of left image) rises nearly 17 miles above the average elevation, making it the tallest known volcano in the solar system.
CAPTION: These three-dimensional images of Mars were produced by bouncing laser light off the surface from orbit. The false colors produce gradient shading designed to bring out the details.
CAPTION: Northern Hemisphere
CAPTION: Southern Hemisphere