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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]
Some 4.5 billion years ago, when Earth was only 100 million years old or so, a Mars-sized protoplanet named Theia smashed into our planet, ejecting loads that eventually returned to the Earth’s ...
Makemake has one moon, discovered in April 2016. A number of other objects in the Kuiper belt and scattered disk may turn out to be dwarf planets. Orcus, Quaoar, Gonggong, and Sedna are generally agreed to be dwarf planets among astronomers, and all but Sedna are known to have moons. [9]
By one estimate, the solar wind has deposited more than 1 million tons of helium-3 (3 He) on the Moon's surface. [62] Materials on the Moon's surface contain helium-3 at concentrations estimated between 1.4 and 15 parts per billion (ppb) in sunlit areas, [1] [63] [64] and may contain concentrations as much as 50 ppb in permanently shadowed ...
Also in 2005, the dwarf planet Haumea was discovered to have two moons, making it the second trans-Neptunian object after Pluto known to have more than one moon. [15] Additionally, 216 Kleopatra [ 16 ] and 93 Minerva [ 17 ] were discovered to be triple asteroids in 2008 and 2009 respectively.
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. NASA's Galileo ' s ...
The Moon is Earth's only natural satellite.It orbits around Earth at an average distance of 384,400 km (238,900 mi), about 30 times the width 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.
Jupiter's outer two Galilean moons Ganymede and Callisto contain more ice since they formed further from the hot proto-Jupiter. Saturn's moon Titan looks and behaves more like Earth than any other body in the Solar System. [5] Titan is known to have stable pools of liquid methane on the surface. [5]