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Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury. In English, Mars carries a name of the Roman god of war, and is often referred to as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

The days and seasons are likewise comparable to those of Earth, because the rotational period as well as the tilt of the rotational axis relative to the ecliptic plane are very similar. Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan.

There are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and Rosalind Franklin rovers. Liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is less than 1% of the Earth's, except at the lowest elevations for short periods. The two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 meters (36 ft). In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.

Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.94, which is surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground-based telescopes are typically limited to resolving features about 300 kilometers (190 mi) across when Earth and Mars are closest because of Earth's atmosphere.

Selected article

Mars 96 (sometimes called Mars 8) was an orbiter launched in 1996 by Russia and not directly related to the Soviet Mars probe program of the same name. The orbiter's intended destination was Mars, but its actual destination was the Pacific Ocean, due to problems with the launch vehicle. The Mars 96 spacecraft was based on the Phobos vehicles launched to Mars in 1988. They were of a new design at the time and both ultimately failed. But for the Mars 96 probe the designers believed they had corrected the flaws of the Phobos vehicle. Alas, they did not get to find out if they had produced a successful design this time due to the launch vehicle failure.

It was, however, a very ambitious mission and the heaviest (intended) interplanetary probe ever launched. It included a large complement of instruments such as the Penetrator, many provided by France, Germany, and other European countries (some of which have since been re-flown on Mars Express, launched in 2003), and the United States. It was made up of the Orbiter, two Surface Stations, and two Penetrators.


Selected biography

Percival Lowell
Percival Lawrence Lowell (March 13, 1855 – November 12, 1916) was a businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death. The choice of the name Pluto and its symbol were partly influenced by his initials PL.

Percival Lowell, a descendant of the Boston Lowell family, was the brother of A. Lawrence, president of Harvard University, and Amy, an imagist poet, critic, and publisher. Percival graduated from the Noble and Greenough School in 1872 and Harvard University in 1876 with distinction in mathematics. At his college graduation, he gave a speech, considered very advanced for its time, on the "Nebular Hypothesis." He was later awarded honorary degrees from Amherst College and Clark University.


Mars Atmosphere ˑ Exploration (Voyager 2) ˑ History

Major Moons ˑ Phobos ˑ Deimos ˑ

Astronomers: Tycho Brahe ˑ Johannes Kepler ˑ Percival Lowell ˑ Gerard Kuiper ˑ Christiaan Huygens

See Also: Formation and evolution of the Solar System ˑ Terrestrial planet ˑ Nebular hypothesis

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Italicized articles are on dwarf planets or minor moons.


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