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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 ...
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
The definition of the Martian prime meridian has since been refined on the basis of spacecraft imagery as the center of the crater Airy-0 in Terra Meridiani. However, Mars does not have time zones defined at regular intervals from the prime meridian, as on Earth.
Celestial north pole on Mars Celestial south pole on Mars The orientation of Mars's axis is such that its north celestial pole is in Cygnus at R.A. 21 h 10 m 42 s Decl. +52° 53.0′ (or more precisely, 317.67669 +52.88378), near the 6th-magnitude star BD +52 2880 (also known as HR 8106, HD 201834, or SAO 33185), which in turn is at R.A. 21 h ...
By the 2nd millennium BCE they were familiar with the apparent retrograde motion of the planet, in which it appears to move in the opposite direction across the sky from its normal progression. [2] Mars was portrayed on the ceiling of the tomb of Seti I, on the Ramesseum ceiling, [3] and in the Senenmut star map. The last is the oldest known ...
Several factors make placing a spacecraft into an areostationary orbit more difficult than a geostationary orbit. Since the areostationary orbit lies between Mars's two natural satellites, Phobos (semi-major axis: 9,376 km) and Deimos (semi-major axis: 23,463 km), any satellites in the orbit will suffer increased orbital station keeping costs due to unwanted orbital resonance effects.
An astronomical example is Pluto's largest moon Charon. [4] Much more commonly, synchronous orbits are employed by artificial satellites used for communication, such as geostationary satellites . For natural satellites, which can attain a synchronous orbit only by tidally locking their parent body, it always goes in hand with synchronous ...
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 ...