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Mars has two relatively small (compared to Earth's) natural moons, Phobos (about 22 kilometres (14 mi) in diameter) and Deimos (about 12 kilometres (7.5 mi) in diameter), which orbit close to the planet. The origin of both moons is unclear, although a popular theory states that they were asteroids captured into Martian orbit.
The maps below were produced by the Mars Global Surveyor ' s Mars Orbiter Laser Altimeter; redder colors indicate higher elevations.The maps of the equatorial quadrangles use a Mercator projection, while those of the mid-latitude quadrangles use a Lambert conformal conic projection, and the maps of the polar quadrangles use a polar stereographic projection.
4.4 Equatorial canyon system. 4.5 Chaotic terrain and outflow channels. ... Over 42,000 impact craters greater than 5 km in diameter have been catalogued on Mars, ...
With an altitude of 5,989 km (3,721 mi), Phobos orbits Mars below the synchronous orbit radius, meaning that it moves around Mars faster than Mars itself rotates. [23] Therefore, from the point of view of an observer on the surface of Mars, it rises in the west, moves comparatively rapidly across the sky (in 4 h 15 min or less) and sets in the ...
[7] [34] Both moons have very circular orbits which lie almost exactly in Mars's equatorial plane, and hence a capture origin requires a mechanism for circularizing the initially highly eccentric orbit, and adjusting its inclination into the equatorial plane, most probably by a combination of atmospheric drag and tidal forces, [35] although it ...
The planet Earth has a rather slight equatorial bulge; its equatorial diameter is about 43 km (27 mi) greater than its polar diameter, with a difference of about 1 ⁄ 298 of the equatorial diameter. If Earth were scaled down to a globe with an equatorial diameter of 1 metre (3.3 ft), that difference would be only 3 mm (0.12 in).
In 1895, he used this data to estimate that the equatorial diameter was 1/190 larger than the polar diameter. [35] [73] In 1911, he refined the value to 1/192. This result was confirmed by American meteorologist Edgar W. Woolard in 1944. [74]
Areography, also known as the geography of Mars, is a subfield of planetary science that entails the delineation and characterization of regions on Mars. [ 1 ] [ 2 ] [ 3 ] Areography is mainly focused on what is called physical geography on Earth; that is the distribution of physical features across Mars and their cartographic representations.