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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.
Geological studies of the Moon are based on a combination of Earth-based telescope observations, measurements from orbiting spacecraft, lunar samples, and geophysical data. . Six locations were sampled directly during the crewed Apollo program landings from 1969 to 1972, which returned 382 kilograms (842 lb) of lunar rock and lunar soil to Earth [8] In addition, three robotic Soviet Luna ...
The Moon is Earth's only natural satellite.It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period (lunar month) with its rotation period at 29.5 Earth days, causing the same side of the Moon to always face Earth.
The Moon's density is substantially less than that of Earth, due to its lack of a large iron core. [3] On Earth , physical and chemical differentiation processes led to a crustal density of approximately 2700 kg/m 3 compared to the 3400 kg/m 3 density of the compositionally different mantle just below, and the average density of the planet as a ...
Size comparison between Tethys(lower left), the Moon (upper left) and Earth. Tethys is the 16th-largest moon in the Solar System, with a radius of 531 km. [6] Its mass is about 6.17 × 10 20 kg (0.000103 Earth mass), [7] which is less than 1% of the Moon. Despite its relatively small mass, it is more massive than all known moons smaller than ...
Of the Solar System's eight planets and its nine most likely dwarf planets, six planets and seven dwarf planets are known to be orbited by at least 300 natural satellites, or moons. At least 19 of them are large enough to be gravitationally rounded; of these, all are covered by a crust of ice except for Earth's Moon and Jupiter's Io. [1]
To support an Earth-like atmosphere for about 4.6 billion years (Earth's current age), a moon with a Mars-like density is estimated to need at least 7% of Earth's mass. [20] One way to decrease loss from sputtering is for the moon to have a strong magnetic field of its own that can deflect stellar wind and radiation belts.
Although the Moon is Earth's only natural satellite, there are a number of near-Earth objects (NEOs) with orbits that are in resonance with Earth. These have been called "second" moons of Earth or "minimoons". [2] [3] 469219 Kamoʻoalewa, an asteroid discovered on 27 April 2016, is possibly the most stable quasi-satellite of Earth. [4]