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 …showed first 75 words of 1038 total…

…showed last 75 words of 1038 total…in the sky like a red danger signal, it is easy to understand why the ancient people identified this object with the god of war-the Romans with Mars, the Greeks with Ares. A Martian day or time it takes to rotate on its axis is about half an hour longer than Earth’s and a Martian year or the time it takes to orbit the sun is about twice that of Earth’s (687 Earth days).