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Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
At the bottom of the mantle lies a basal liquid silicate layer approximately 150–180 km thick. [44] [54] Mars's iron and nickel core is completely molten, with no solid inner core. [55] [56] It is around half of Mars's radius, approximately 1650–1675 km, and is enriched in light elements such as sulfur, oxygen, carbon, and hydrogen. [57] [58]
The gravitational constant GM (μ) for Mars has the value of 42 830 km 3 s −2, its equatorial radius is 3 389.50 km and the known rotational period (T) of the planet is 1.025 956 76 Earth days (88 642.66 s). Using these values, Mars' orbital altitude is equal to 17 039 km. [73]
On this assumption, a two-year return is not possible for some years, and for some years a delta-v kick of 0.6 to 2.7 km/s at Mars may be needed to get back to Earth. [10] NASA published the Design Reference Architecture 5.0 for Mars in 2009, advocating a 174-day transfer to Mars, which is close to Zubrin's proposed trajectory. [11]
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. [3] [4] [5] 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.
For a stationary synchronous orbit: = [2] G = Gravitational constant m 2 = Mass of the celestial body T = rotational period of the body = Radius of orbit. By this formula one can find the stationary orbit of an object in relation to a given body.
A taxi would need to accelerate to 15,000 miles per hour (6.7 km/s) around Earth, and 22,000 miles per hour (9.8 km/s) near Mars. To get around this, Aldrin proposed what he called a semi-cycler, in which the castle would slow down around Mars, orbiting it, and later resume the cycler orbit. This would require fuel to execute the braking and re ...
For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 km with a density of 0.5 g/cm 3, its true mass would be only 1.12 × 10 19 kg.