Mars is the fourth planet from the sun at about 228 million-km (141 million miles) and the last terrestrial planet from the sun. The next five planets in order from the sun are gaseous. Mars follows closely behind Earth but is comparatively smaller, with about half the diameter of Earth and about one-tenth of Earth’s mass. Thus the force of gravity on Mars is about one-third of that on Earth. Though it is much smaller, Mars does have the same surface land area as Earth. Other than Earth, Mars posses the most highly varied and inter ....