This image, taken by the camera on the Mars Global Surveyor, shows the martian volcano Arsia Mons on the right of the frame. Towering some 30,000 feet (9 kilometers) above the surrounding plains, Arsia Mons is one of the largest volcanoes known. The volcano's summit -- a large crater called a caldera -- is approximately 68 miles (110 kilometers) across.

The whitish haze near the bottom of the picture is created by wispy clouds of water ice above the volcano. They are a common sight every martian afternoon in the region near the equator.