Named after the Roman god of war, the planet Mars is located four planets from the Sun. Commonly referred to as “The Red Planet,” Mars tends to give off a reddish hue when viewed from Earth. This is believed to be caused by an abundance of iron oxide on the planet’s surface. Mars is about half the size of the Earth. Mars has two moons, Phobos and Deimos, both of which are relatively small in size and not shaped in perfect spheres like the Earth’s moon. Mars can be easily seen from Earth without a telescope at a brightness that is only surpassed by the planet Venus, the Moon and the Sun.
Mars has long been considered the most realistic location for life in our solar system, aside from Earth. Many even believe that intelligent life may have once existed on the planet. Scientific exploration of Mars has not produced any evidence of life on the planet. It is believed that the harsh surface environment and extreme solar radiation that saturates the surface of the planet is not capable of sustaining any kind of life. Before space exploration, Mars was considered the best candidate for harboring extraterrestrial life. Astronomers thought they saw straight lines crisscrossing its surface. This led to the popular belief that irrigation canals on the planet had been constructed by intelligent beings. In 1938, when Orson Welles broadcasted a radio drama based on the science fiction classic War of the Worlds by H.G. Wells, enough people believed in the tale of invading Martians to cause a near panic. The average recorded temperature on Mars is -63° C (-81° F) with a maximum temperature of 20° C (68° F) and a minimum of -140° C (-220° F).
Barometric pressure varies at each landing site on a semiannual basis. Carbon dioxide, the major constituent of the atmosphere, freezes out to form an immense polar cap, alternately at each pole. The carbon dioxide forms a great cover of snow and then evaporates again with the coming of spring in each hemisphere. When the southern cap was largest, the mean daily pressure observed by Viking Lander 1 was as low as 6.8 millibars; at other times of the year it was as high as 9.0 millibars. The pressures at the Viking Lander 2 site were 7.3 and 10.8 millibars. In comparison, the average pressure of the Earth is 1000 millibars.
