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The prefix areo-derives from Ares, the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified. The modern Greek word for Mars is Άρης (Áris). As with all synchronous orbits, an areosynchronous orbit has an orbital period equal in length to the primary's sidereal day.
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 average duration of the day-night cycle on Mars — i.e., a Martian day — is 24 hours, 39 minutes and 35.244 seconds, [3] equivalent to 1.02749125 Earth days. [4] The sidereal rotational period of Mars—its rotation compared to the fixed stars—is 24 hours, 37 minutes and 22.66 seconds. [4]
It is slightly shorter than the sidereal year due to the precession of Mars' rotational axis. The precession cycle is 93,000 Martian years (175,000 Earth years), much longer than on Earth. Its length in tropical years can be computed by dividing the difference between the sidereal year and tropical year by the length of the tropical year.
At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. [188] Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years. [189] Mars has its closest approach to Earth in a synodic period of 779.94 days.
New images from NASA’s Mars Reconnaissance Orbiter may show where life first began on Mars. The site on southern Mars shows massive deposits in a basin that scientists say were formed a long ...
By comparison, the Sun has an apparent size of about 0.35° in the Martian sky. Phobos' phases, inasmuch as they can be observed from Mars, take 0.3191 days (Phobos' synodic period) to run their course, a mere 13 seconds longer than Phobos' sidereal period.
In astronomy, the rotation period or spin period [1] of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space).