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Mars as photographed by the Hubble telescope.
Mars is the fourth planet from the Sun in our solar system. It is named after the Roman god of war Mars (Ares in Greek mythology) because of its apparent red color. This feature has also earned it the nickname "The Red Planet". The prefix areo- refers to Mars in the same way geo- refers to Earth. The astronomical symbol for Mars is ♂, a circle with an arrow pointing northeast. The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as 火星, or fire star. Mars is a terrestrial planet with a thin atmosphere, having surface features such as craters, giant valleys, and volcanoes. Of all the planets in our Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life.

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Phobos moon (large).jpg
Phobos is the larger and closer of Mars' two moons (the other being Deimos), both discovered by Asaph Hall. It is named after the Greek god Phobos (which means "fear"), a son of Ares (Mars). Its surface is mostly composed of carbonaceous chondrites and is heavily cratered. Phobos is one of the smallest moons in the solar system, and orbits about 9377 km (5823 mi) above the surface of Mars, closer to its primary than any other planetary moon. Because of this close orbit, the moon will crash into Mars' surface in the future. Phobos can cast shadows onto the surface of Mars when it passes between the Sun and Mars. Phobos' origin is unclear, and has been identified as a captured asteroid or even the remains of a planetesimal. One debunked claim suggested that Phobos is of artificial origin and is hollow. Spacecraft have imaged Phobos while orbiting Mars. The Phobos spacecraft were meant to explore Phobos in greater detail, but both failed en route. There are future plans to explore this moon.

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A painting of Tycho Brahe.
Tycho Brahe About this sound listen  (14 December 1546 – 24 October 1601), born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations. Coming from Scania, then part of Denmark, now part of modern-day Sweden, Tycho was well known in his lifetime as an astronomer and alchemist.

In his De nova stella (Of new stars) of 1573, he refuted the theory of the celestial spheres by showing the celestial heavens were not in an immutable or unchanging state of perfection as previously assumed by Aristotle and Ptolemy. His precise measurements indicated that "new stars" (now known as novae or supernovae), in particular that of 1572, lacked the parallax expected in sub-lunar phenomenon, and were therefore not "atmospheric" tail-less comets as previously believed, but occurred above the atmosphere and moon. Using similar measurements he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposed "immutable" celestial spheres.


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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