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It is classified as a terrestrial planet and is the second smallest of the Solar System 's planets with a diameter of 6,779 km (4,212 mi). In terms of orbital motion, a Martian solar day (sol) is equal to 24.5 hours, and a Martian solar year is equal to 1.88 Earth years (687 Earth days).
Mars has an orbit with a semimajor axis of 1.524 astronomical units (228 million km) (12.673 light minutes), and an eccentricity of 0.0934. [1][2] The planet orbits the Sun in 687 days [3] and travels 9.55 AU in doing so, [4] making the average orbital speed 24 km/s. The eccentricity is greater than that of every other planet except Mercury ...
Substituting the mass of Mars for M and the Martian sidereal day for T and solving for the semimajor axis yields a synchronous orbit radius of 20,428 km (12,693 mi) above the surface of the Mars equator. [4] [5] [6] Subtracting Mars's radius gives an orbital altitude of 17,032 km (10,583 mi). Two stable longitudes exist - 17.92°W and 167.83°E.
The northern polar cap has a diameter of approximately 1,000 km during the northern Mars summer, [110] and contains about 1.6 million cubic kilometres of ice, which if spread evenly on the cap would be 2 km thick. [111] (This compares to a volume of 2.85 million cubic kilometres for the Greenland ice sheet.)
The mean radius in astronomy is a measure for the size of planets and small Solar System bodies. Alternatively, the closely related mean diameter ( ), which is twice the mean radius, is also used. For a non-spherical object, the mean radius (denoted or ) is defined as the radius of the sphere that would enclose the same volume as the object. [1]
The quadrangles appear as rectangles on maps based on a cylindrical map projection, [1] but their actual shapes on the curved surface of Mars are more complicated Saccheri quadrilaterals. The sixteen equatorial quadrangles are the smallest, with surface areas of 4,500,000 square kilometres (1,700,000 sq mi) each, while the twelve mid-latitude ...
Mars has a higher scale height of 11.1 km than Earth (8.5 km) because of its weaker gravity. [5] The theoretical dry adiabatic lapse rate of Mars is 4.3 °C km −1, [129] but the measured average lapse rate is about 2.5 °C km −1 because the suspended dust particles absorb solar radiation and heat the air. [2]
Mars Reconnaissance Orbiter. The Mars Reconnaissance Orbiter (MRO) is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA 's Mars Exploration Program. It was launched from Cape Canaveral on August 12, 2005, at 11:43 UTC and reached Mars on March 10, 2006, at 21:24 UTC.