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Substituting the mass of Mars for M and the Martian sidereal day for T and solving for the semimajor axis yields a synchronous orbit radius of 20,428 km (12,693 mi) above the surface of the Mars equator. [3] [4] [5] Subtracting Mars's radius gives an orbital altitude of 17,032 km (10,583 mi). Two stable longitudes exist - 17.92°W and 167.83°E.
Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, the mean radius is = (( ) ) / = . The equatorial and polar radii of a planet are often denoted r e {\displaystyle r_{e}} and r p {\displaystyle r_{p}} , respectively.
Mars has an axial tilt of 25.19°, quite close to the value of 23.44° for Earth, and thus Mars has seasons of spring, summer, autumn, winter as Earth does. As on Earth, the southern and northern hemispheres have summer and winter at opposing times. However, the orbit of Mars has significantly greater eccentricity than that of Earth. Therefore ...
The planets come into opposition near Mars's perihelion in 2003, 2018 and 2035, with the 2020 and 2033 events being particularly close to perihelic opposition. [192] [193] [194] Mars seen through a 16-inch amateur telescope, at 2020 opposition. The mean apparent magnitude of Mars is +0.71 with a standard deviation of 1.05. [19]
Deimos (/ ˈ d aɪ m ə s /; systematic designation: Mars II) [11] is the smaller and outer of the two natural satellites of Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars. [5] Deimos is 23,460 km (14,580 mi) from Mars, much farther than Mars's other moon, Phobos. [12]
Vesta (radius 262.7 ± 0.1 km), the second-largest asteroid, appears to have a differentiated interior and therefore likely was once a dwarf planet, but it is no longer very round today. [74] Pallas (radius 255.5 ± 2 km ), the third-largest asteroid, appears never to have completed differentiation and likewise has an irregular shape.
For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 km with a density of 0.5 g/cm 3, its true mass would be only 1.12 × 10 19 kg.