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This ring system may have originated from a large asteroid that passed by Earth at this time and had a significant amount of debris stripped by Earth's gravitational pull, forming a ring system. Evidence for this ring comes from impact craters from the Ordovician meteor event appearing to cluster in a distinctive band around the Earth's equator ...
Of the inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos. The giant planets have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four Galilean moons , Saturn's ...
The 19 moons that are known to be large enough to have been rounded by their own gravity are listed in bold. The seven largest moons, which are larger than any of the known dwarf planets, are listed in bold and italic. Sidereal period differs from semi-major axis because a moon's speed depends both on the mass of its primary and its distance ...
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]
The Earth's Moon and Jupiter's moon Io have similar structures to terrestrial planets, but Earth's Moon has a much smaller iron core. Another Jovian moon Europa has a similar density but has a significant ice layer on the surface: for this reason, it is sometimes considered an icy planet instead.
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.
Venus is similar in size and distance from the sun when compared with Earth, and some researchers believe the planet might have even had an Earth-like climate at some point.
Venus and Earth have the lowest difference in gravitational potential of any pair of Solar System planets. This allows Venus to be the most accessible destination and a useful gravity assist waypoint for interplanetary flights from Earth. Venus figures prominently in human culture and in the history of astronomy.