geologia: Miranda (moon)

Evidence: 100 • authority: 72

Miranda is the smallest and innermost of Uranus's five round satellites. It was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory in Texas, and named after Miranda from William Shakespeare's play The Tempest. Like the other large moons of Uranus, Miranda orbits close to its planet's equatorial plane. Because Uranus orbits the Sun on its side, Miranda's orbit is nearly perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle. At just 470 km (290 mi) in diameter, Miranda is one of the smallest closely observed objects in the Solar System that might be in hydrostatic equilibrium (spherical under its own gravity), and its total surface area is roughly equal…

Evidence: 45 • authority: 72

This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius. These lists can be sorted according to an object's radius and mass and, for the most massive objects, volume, density, and surface gravity, if these values are available. These lists contain the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects. Many trans-Neptunian objects (TNOs) have been discovered; in many cases their positions in this list are appro…

Evidence: 38 • authority: 72

This is a list of most likely gravitationally rounded objects (GRO) of the Solar System, which are objects that have a rounded, ellipsoidal shape due to their own gravity (but are not necessarily in hydrostatic equilibrium). Apart from the Sun itself, these objects qualify as planets according to common geophysical definitions of that term. The radii of these objects range over three orders of magnitude, from planetary-mass objects like dwarf planets and some moons to the planets and the Sun. This list does not include small Solar System bodies, but it does include a sample of possible planetary-mass objects whose shapes have yet to be determined. The Sun's orbital characteristics are liste…

Evidence: 38 • authority: 72

There are currently 29 known moons of the planet Uranus. The 27 with names are named after characters that appear in, or are mentioned in, William Shakespeare's plays and Alexander Pope's poem The Rape of the Lock. Uranus's moons are divided into three groups: fourteen inner moons, five major moons, and ten irregular moons. The inner and major moons all have prograde orbits and are cumulatively classified as regular moons. In contrast, the orbits of the irregular moons are distant, highly inclined, and mostly retrograde. The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are ellipsoidal, indicating that they reached hydro…

Evidence: 38 • authority: 72

A planetary-mass moon is a planetary-mass object that is a natural satellite of another non-stellar celestial object. Because of their mass, these moons are large and ellipsoidal (sometimes spherical) in shape due to hydrostatic equilibrium caused by internal partial melting and differentiation and/or from tidal or radiogenic heating, in some cases forming a subsurface ocean. Planetary-mass moons are sometimes called satellite planets by some planetary scientists such as Alan Stern, who are more concerned with whether a celestial body has planetary geology (that is, whether it is a planetary body) than its solar or non-solar orbit (planetary dynamics). Thus they consider planetary-mass moon…

Evidence: 25 • authority: 72

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 468 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. Several of the largest ones are in hydrostatic equilibrium and would therefore be considered dwarf planets or planets if they were in direct orbit around the Sun and not in their current states (orbiting planets or dwarf planets).

Evidence: 25 • authority: 92

Neptune's inner moons and rings are exposed icy body interiors.. Neptune's single large moon, Triton, is accompanied by a set of dusty rings and small moons whose composition and origin are uncertain. Using the James Webb Space Telescope, we observed Neptune's rings and three moons: Larissa, Galatea, and Proteus. These moons and rings have spectra that are distinct from other outer Solar System objects and show no evidence of water ice despite hosting deep 3-micrometer OH absorption bands. In addition, Larissa, Galatea, and the rings show a compositional signature unique among outer Solar System bodies: a 2.72-micrometer absorption band diagnostic of magnesium-rich phyllosilicates-a signpos…

Evidence: 25 • authority: 72

An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters are typically circular, though they can be elliptical in shape or even irregular due to events such as landslides. Impact craters range in size from microscopic craters seen on lunar rocks returned by the Apollo Program to simple bowl-shaped depressions and vast, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact…