Mars (IPA: /ˈmɑrz/) is the fourth planet from the Sun in the Solar System and could become habitable in the future. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance as seen from Earth because of large amounts of iron oxide. A small terrestrial planet, Mars has a thin carbon dioxide rich 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 is home to Olympus Mons, the highest known mountain in the solar system, and Valles Marineris, the largest canyon. In addition to its geographical features, Mars’s rotational period and seasonal cycles are likewise similar to those of the Earth. Mars is on average 142 million miles from the sun which is further and colder than Earth. The distance varies between its perihelion 129 million miles and its aphelion 160 million miles. Despite its small size and relatively low temperatures life can't be ruled out there and many serious NASA scientists are searching for life on Mars, though most Exobiologists think life is more likely under the surface of the Jovian Moon Europa.
Until the first flyby of Mars by Mariner 4 in 1965, it was speculated that there might be liquid water on the planet. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, Mars is likely to harbor life. Mars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. This is more than any planet except Earth. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity). Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred in recent years. Observations by the now dead NASA's Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding.
Mars has two moons, Phobos and Deimos, both of which are small and irregularly shaped. These are likely to be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −2.9, a brightness surpassed only by Venus, the Moon, and the Sun, though for much of the year Jupiter may appear brighter to the naked eye than Mars.