An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1 Search : Mars'' calendar
Mars' calendar
  گاهشمار ِ بهرام   
gâhšomâr-e Bahrâm

Fr.: calendrier martien   

A special calendar for time reckoning on Mars in which the year consists of 668 → sols (687 Earth days) and each sol has 24h 39m 35s. For convenience, sols are divided into a 24-hour clock. Each landed Mars mission keeps track of local solar time at its landing site, which depends upon the lander's longitude of Mars. The Martian year begins when Mars arrives at the → vernal point of the orbit in its northward journey; in other words, when the solar longitude Ls is 0°. Mars' other seasons begin when Ls = 90° at → summer solstice, 180° at → autumn equinox, and 270° at → winter solstice. The year counts begin at Mars Year 1, at the northern → vernal equinox of April 11, 1955. The second half of that year was marked by a major dust storm (→ Mars' dust storm). February 7, 2021 marked the start of Year 36 on Mars. Year 37 will start on Dec. 26, 2022, and Year 38 on Nov. 12, 2024. On Earth, spring, summer, autumn, and winter are all similar in length, because Earth's orbit is nearly circular (→ eccentricity = 0.0167), so it moves at nearly constant speed around the Sun. By contrast, Mars' elliptical orbit (→ eccentricity = 0.0934) makes its distance from the Sun change with time, and also makes it speed up and slow down in its orbit. Mars is at → aphelion (249,200,000 km from Sun) at Ls = 70°, near the northern summer solstice, and at → perihelion (206,700,000 km) at Ls = 250°, near the southern summer solstice. The Mars dust storm season begins just after perihelion at around Ls = 260°.

Mars; → calendar.