This elevation map shows a pronounced difference between the northern and southern hemispheres of Mars. The average elevation of the northern hemisphere is miles lower than the southern (lower elevations are in blue and green, higher in orange and red). The dichotomy could be the result of a collision between Mars and another planet in the early solar system. The highest elevations represent giant volcanoes (which circles at left). A long system of deep canyons, Valles Marineris, extends to the right of the volcano complex. The large, dark oval at right is Hellas Basin, a giant impact crater, which represents the lowest area on the entire planet. [NASA/GSFC]