Portal:Astronomy/Featured/May 2007
Mars (IPA: /ˈmɑɹz/ (GenAm); /ˈmɑːz/ (RP)) is the fourth planet from the Sun and is known as the Red Planet due to its reddish appearance as seen from Earth. The planet is named after Mars, the Roman god of war. A terrestrial planet, Mars has a thin atmosphere and surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It has the highest mountain in the solar system, Olympus Mons, and the largest canyon, Valles Marineris. Mars' rotational period and seasonal cycles are also similar to those of the Earth.
Until the first flyby of Mars by Mariner 4 in 1965, it was speculated that there might be liquid water on Mars. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents. Also, long dark striations were interpreted by some observers as irrigation channels of liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, of all the planets in the Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life.
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