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Mars is the only other planet to have had its surface explored by a mobile surface probe (rover). Titan is the only non-planetary object of planetary mass to have been explored by lander. Landers have explored several smaller bodies including 433 Eros (2001), 25143 Itokawa (2005), Tempel 1 (2005), 67P/Churyumov–Gerasimenko (2014), 162173 ...
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. [1] [2] The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System.
Planets whose orbits lie within the orbit of Earth. [nb 1] Mercury and Venus: Inner planet: A planet in the Solar System that have orbits smaller than the asteroid belt. [nb 2] Mercury, Venus, Earth, Mars: Outer planet: A planet in the Solar System beyond the asteroid belt, and hence refers to the gas giants. Jupiter, Saturn, Uranus and Neptune ...
Jupiter's magnetic field is the strongest of any planet in the Solar System, [102] with a dipole moment of 4.170 gauss (0.4170 mT) that is tilted at an angle of 10.31° to the pole of rotation. The surface magnetic field strength varies from 2 gauss (0.20 mT) up to 20 gauss (2.0 mT). [123]
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope. [16] A low-mass gas planet can still have a radius resembling that of a gas giant if it has the right temperature. [17]
The structure of rocky planets is constrained by the average density of a planet and its moment of inertia. [15] The moment of inertia for a differentiated planet is less than 0.4, because the density of the planet is concentrated in the center. [16] Mercury has a moment of inertia of 0.346, which is evidence for a core. [17]
A type of solid planet with an icy surface of volatiles. In the Solar System, most planetary-mass moons (such as Titan, Triton, and Enceladus) and many dwarf planets (such as Pluto and Eris) have such a composition. Europa is sometimes considered an icy planet due to its surface ice, but its higher density indicates that its interior is mostly ...
In planetary science, the term geology is used in its broadest sense, to mean the study of the surface and interior parts of planets and moons, from their core to their magnetosphere. The best-known research topics of planetary geology deal with the planetary bodies in the near vicinity of the Earth: the Moon , and the two neighboring planets ...