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Definition of year and seasons. The length of time for Mars to complete one orbit around the Sun in respect to the stars, its sidereal year, is about 686.98 Earth solar days (≈ 1.88 Earth years), or 668.5991 sols. Because of the eccentricity of Mars' orbit, the seasons are not of equal length.
Mars sol. Sol (borrowed from the Latin word for sun) is a solar day on Mars; that is, a Mars-day. A sol is the apparent interval between two successive returns of the Sun to the same meridian (sundial time) as seen by an observer on Mars. It is one of several units for timekeeping on Mars. A sol is slightly longer than an Earth day.
Mars reaches opposition when there is a 180° difference between the geocentric longitudes of it and the Sun. At a time near opposition (within 8½ days) the Earth–Mars distance is as small as it will get during that 780-day synodic period. [7]
The United States Naval Observatory states "the Equation of Time is the difference apparent solar time minus mean solar time", i.e. if the sun is ahead of the clock the sign is positive, and if the clock is ahead of the sun the sign is negative. [6] [7] The equation of time is shown in the upper graph above for a period of slightly more than a ...
The "width" of the figure is due to the equation of time, and its angular extent is the difference between the greatest positive and negative deviations of local solar time from local mean time when this time-difference is related to angle at the rate of 15° per hour, i.e., 360° in 24 h. This width of the analemma is approximately 7.7°, so ...
The basic time periods from which the calendar is constructed are the Martian solar day (sometimes called a sol) and the Martian vernal equinox year.The sol is 39 minutes 35.244 seconds longer than the Terrestrial solar day, and the Martian vernal equinox year is 668.5907 sols in length (which corresponds to 686.9711 days on Earth).
The zodiac constellations of Mars's ecliptic are almost the same as those of Earth — after all, the two ecliptic planes only have a mutual inclination of 1.85° — but on Mars, the Sun spends 6 days in the constellation Cetus, leaving and re-entering Pisces as it does so, making a total of 14 zodiacal constellations.
On a prograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). More simply, 1→2 is a complete ...