types of terrain: relatively bright highlands and darker plains. Current knowledge of the Moon is greater than for any other solar system object except Earth. This lends to a greater understanding of geologic processes and further appreciation of the complexity of terrestrial planets. The relatively bright, heavily cratered highlands are called terrae. The craters and basins in the highlands are formed by meteorite. MarsMars is the fourth planet from the Sun and the seventh largest. Mars is sometimes referred to as the Red Planet. The name of the month March derives from Mars. Mars has been known since prehistoric times. Except for Earth, Mars has the most highly varied and interesting terrain of any of the terrestrial planets. One being Olympus Mons, the largest mountain in the Solar System rising 24 km (78,000 ft.) above the surrounding plain. Like Mercury and the Moon, Mars appears to lack active plate tectonics at present; there is no evidence of recent horizontal motion of the surface such as the folded mountains so common on Earth. JupiterJupiter is named after the king of the Roman gods. It is the largest planet in the Solar System, the fifth planet from the Sun and the first of the outer planets Jupiter has had a dominant effect on a large part of the Solar System. It is likely that Jupiter's huge gravity has prevented a planet from forming in the area now occupied by the Asteroid Belt. Jupiter has a magnetic field 20,000 times stronger than that of the Earth's, having a devastating effect on its moons. SaturnSaturn is the sixth planet from the Sun and the second largest: In Roman mythology, Saturn is the god of agriculture and has been known since prehistoric times. Galileo was the first to observe it with a telescope in 1610; he noted its odd appearance but was confused by it. Early observations of Saturn were complicated by the fact that the Earth passes through the plane of Saturn's rings every few years as Saturn moves in i...
