by a splitting of the planetΓÇÖs crust, probably resulting from ancient plate shifting similar to that still seen on Earth.
The dark oval-shaped forma- tions near the edge of the planet are shield volcanosΓÇölarge, gently sloping mountains created by the outward flow of lava. The largest Martian volcano is Mons Olympus, which, with a height of 25 kilometers (two and a half times as high as Mount Everest) and a base 600 kilometers across, is the largest known volcano in the solar system.
At an average distance of about 292 million kilometers from the Sun, Mars receives only about 43 percent as much solar radiation as Earth. Near MarsΓÇÖs equator, the average temperature is from 190
