Mars is the fourth planet from the Sun and is commonly referred to as the Red Planet. Mars is a small rocky body once thought to be very Earthlike.The rocks, soil and sky have a red or pink hue. The distinct red color was observed by stargazers throughout history. It was given its name by the Romans in honor of their god of war. Other civilizations have had similar names. The ancient Egyptians named the planet Her Descher meaning the red one.Mars can easily be seen from Earth with the naked eye.Mars has an average opposition distance of 78 million km but can come as close as 55.7 million km during a close approach, such as occurred in 2003.
Mars' orbit is significantly elliptical. One result of this is a temperature variation of about 30 C at the subsolar point between aphelion and perihelion. This has a major influence on Mars' climate. While the average temperature on Mars is about 218 °K (-55 °C, -67 °F), Martian surface temperatures range widely from as little as 140 °K (-133 °C, -207 °F) at the winter pole to almost 300 °K (27 °C, 80 °F) on the dayside during summer. Though Mars is much smaller than Earth, its surface area is about the same as the land surface area of Earth.Mars has some remarkable geological characteristics, including the largest volcanic mountain in the solar system, Olympus Mons; volcanoes in the northern Tharsis region that are so huge they deform the planet's roundness; and a gigantic equatorial rift valley, the Valles Marineris. This canyon system stretches a distance equivalent to the distance from New York to Los Angeles; Arizona's Grand Canyon could easily fit into one of the side canyons of this great chasm.
Mars has the largest canyon in the solar system. It would reach from Los Angeles to Chicago if it was on Earth. Mars has a very thin atmosphere, mostly carbon dioxide, but dust storms can cover the whole planet for months at a time. About every two years the Earth and Mars come close together. The planet has two moons, Diemos and Phobos.Although no one knows how they formed, they may be asteroids snared by Mars's gravity.
