How is Mars different from Earth?

Mars is smaller, about half the size of Earth, with a radius of 2,108 miles (3,393 kilometers) compared to 3,963 miles (6,378 kilometers) for Earth. Because of its small size, Mars' interior cooled more quickly than Earth's, and thus it has less volcanic activity than Earth. The red planet also has no plate tectonics. Its crust is rigid, unlike the constantly moving crust of Earth. Therefore, Mars does not have extensive mountain chains, oceans, or lines of volcanoes, such as those found on Earth. Mars does, however, hold the distinction of having the tallest mountain on any planet in the solar system. Olympus Mons, at 14 miles (22 kilometers) tall is nearly three times as high as Mount Everest in Nepal.