Mars Through New Eyes

On the Cover: Generated by the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard NASA's <i>Mars Global Surveyor</i>, this high-resolution map of Mars represents 27 million elevations measurements gathered in 1998 and 1999. The datum, or Martian sea-level, is marked by medium blue, most easily seen at the right edge of the image. Darker blue to violet tones indicate areas that are more than 3,000 meters higher than the datum. The massive Hellas impact basin (bottom left) is deep enough to swallow Mount Everest—nearly 9 kilometers (6 miles) deep and 2,100 kilometers (1,300 miles) wide. The basin is surrounded by a ring of ejected material that rises about 2 kilometers (1.25 miles) above the surroundings and stretches out to 4,000 kilometers (2,500 miles) from the basin center. The Valles Marineris canyon system (top center) slopes away from nearby outflow channels where water once flowed in early Martian history, with part of it lying about 1 kilometer (roughly, half a mile) below the level of these channels. The large blue area (right) is the low, smooth northern polar region, surprisingly different than the southern hemisphere (left), which is heavily cratered and sits, on average, about 5 kilometers (3 miles) higher than the north.