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The history of observations of Mars is marked by oppositions of Mars when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the perihelic oppositions of Mars, which are distinguished because Mars is close to perihelion, making it even closer to Earth. [192]
Yellow clouds on Mars have been observed since the 1870s, which Eugène M. Antoniadi suggested were windblown sand or dust. During the 1920s, the range of Martian surface temperature was measured; it ranged from −85 to 7 °C (−121 to 45 °F). The planetary atmosphere was found to be arid with only trace amounts of oxygen and water.
Extra-close oppositions of Mars happen every 15 to 17 years, when we pass between Mars and the Sun around the time of its perihelion (closest point to the Sun in orbit). The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost ...
The apsides refer to the farthest (2) and nearest (3) points reached by an orbiting planetary body (2 and 3) with respect to a primary, or host, body (1). An apsis (from Ancient Greek ἁψίς (hapsís) 'arch, vault'; pl. apsides / ˈ æ p s ɪ ˌ d iː z / AP-sih-deez) [1] [2] is the farthest or nearest point in the orbit of a planetary body about its primary body.
As on Earth, there is a second form of precession: the point of perihelion in Mars's orbit changes slowly, causing the anomalistic year to differ from the sidereal year. However, on Mars, this cycle is 43,000 Martian years (81,000 Earth years) rather than 112,000 years as on Earth.
The current perihelion, near January 4, is fairly close to the solstice of December 21 or 22. ... Small also claimed, against the history, ... 7.496 Mars 1.52366 686. ...
Mars 4 flew by the planet at a range of 2200 km returning one swath of pictures and radio occultation data, which constituted the first detection of the nightside ionosphere on Mars. [49] Mars 7 probe separated prematurely from the carrying vehicle due to a problem in the operation of one of the onboard systems (attitude control or retro ...
They proposed dividing the history of Mars into three eras: the Phyllocian, Theiikian and Siderikan. [ 17 ] [ 18 ] The Phyllocian (named after phyllosilicate or clay minerals that characterize the era) lasted from the formation of the planet until around the Early Noachian (about 4.0 Gya).