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Rheasilvia (crater)
Rheasilvia is the most prominent surface feature on the asteroid Vesta and is thought to be an impact crater. It is in diameter, which is 90% the diameter of Vesta itself, and is 95% the mean diameter of Vesta, . However, the mean is affected by the crater itself. It is 89% the mean equatorial diameter of , making it one of the largest craters in the Solar System, and at 75°S latitude, covers most of the southern hemisphere. The peak in the center of the crater is in diameter, and rises from its base, making it one of the tallest mountains known in the Solar System. Discovery Rheasilvia was discovered in Hubble Space Telescope images in 1997, but was not named until the arrival of the ''Dawn'' spacecraft in 2011. It is named after Rhea Silvia, a mythological vestal virgin and mother of the founders of Rome, Romulus and Remus.(NASA coordinates) Characteristics The crater partially obscures an earlier crater, named Veneneia, that at is almost as large. Rheasil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Tallest Mountains In The Solar System
This is a list of the tallest mountains in the Solar System. This list includes peaks on all celestial bodies where significant mountains have been detected. For some celestial bodies, different peaks are given across different types of measurement. The solar system's tallest mountain is the central peak of Rheasilvia on the asteroid Vesta, estimated at up to 25 km from peak to base. Among the terrestrial planets the tallest mountain is Olympus Mons on Mars, at 21.9 km. __TOC__ List Heights are given from base to peak (although a precise definition for mean base level is lacking). Peak elevations above sea level are only available on Earth, and possibly Titan. On other worlds, peak elevations above an equipotential surface or a reference ellipsoid could be used if enough data is available for the calculation, but this is often not the case. Tallest mountains by elevation * Olympus Mons * Equatorial Ridge * Boösaule Mons * Ascraeus Mons * Ionian Mons * Elysium Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle (geology)
A mantle is a layer inside a planetary body bounded below by a Planetary core, core and above by a Crust (geology), crust. Mantles are made of Rock (geology), rock or Volatiles, ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone planetary differentiation, differentiation by density. All Terrestrial planet, terrestrial planets (including Earth), a number of Asteroid, asteroids, and some planetary Natural satellite, moons have mantles. Earth's mantle The Earth's mantle is a layer of Silicate minerals, silicate rock between the Crust (geology), crust and the Earth's outer core, outer core. Its mass of 4.01 × 1024 kg is 67% the mass of the Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly solid, but in Geologic time scale, geological time it behaves as a Viscosity, viscous fluid. Partial melting of the mantle at mid-ocean ridges produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rheasilvia And Older Basin, Vesta
Rheasilvia is the most prominent surface feature on the asteroid Vesta and is thought to be an impact crater. It is in diameter, which is 90% the diameter of Vesta itself, and is 95% the mean diameter of Vesta, . However, the mean is affected by the crater itself. It is 89% the mean equatorial diameter of , making it one of the largest craters in the Solar System, and at 75°S latitude, covers most of the southern hemisphere. The peak in the center of the crater is in diameter, and rises from its base, making it one of the tallest mountains known in the Solar System. Discovery Rheasilvia was discovered in Hubble Space Telescope images in 1997, but was not named until the arrival of the ''Dawn'' spacecraft in 2011. It is named after Rhea Silvia, a mythological vestal virgin and mother of the founders of Rome, Romulus and Remus.(NASA coordinates) Characteristics The crater partially obscures an earlier crater, named Veneneia, that at is almost as large. Rheasilvia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Pressure
Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules). The associated force is called the radiation pressure force, or sometimes just the force of light. The forces generated by radiation pressure are generally too small to be noticed under everyday circumstances; however, they are important in some physical processes and technologies. This particularly includes objects in outer space, where it is usually the main force acting on objects besides gravity, and where the net effect of a tiny force may have a large cumulative effect over long periods of time. For example, had the effects of the Sun's radiation pressure on the spacecraft of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yarkovsky Effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids (about 10 cm to 10 km in diameter), as its influence is most significant for these bodies. History of discovery The effect was discovered by the Polish-Russian civil engineer Ivan Osipovich Yarkovsky (1844–1902), who worked in Russia on scientific problems in his spare time. Writing in a pamphlet around the year 1900, Yarkovsky noted that the daily heating of a rotating object in space would cause it to experience a force that, while tiny, could lead to large long-term effects in the orbits of small bodies, especially meteoroids and small asteroids. Yarkovsky's insight would have been forgotten had it not been for the Estonian astronomer Ernst J. Öpik (1893–1985), who read Yarkovsky's pamphlet sometime around 1909. Decades later, Öpik, recalling t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kirkwood Gap
A Kirkwood gap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter. For example, there are very few asteroids with semimajor axis near 2.50 AU, period 3.95 years, which would make three orbits for each orbit of Jupiter (hence, called the 3:1 orbital resonance). Other orbital resonances correspond to orbital periods whose lengths are simple fractions of Jupiter's. The weaker resonances lead only to a depletion of asteroids, while spikes in the histogram are often due to the presence of a prominent asteroid family ''(see List of asteroid families)''. The gaps were first noticed in 1866 by Daniel Kirkwood, who also correctly explained their origin in the orbital resonances with Jupiter while a professor at Jefferson College in Canonsburg, Pennsylvania. Most of the Kirkwood gaps are depleted, unlike the mean-motion resonances ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HED Meteorite
HED meteorites are a clan (subgroup) of achondrite meteorites. HED stands for "howardite–eucrite–diogenite". These achondrites came from a differentiated parent body and experienced extensive igneous processing not much different from the magmatic rocks found on Earth and for this reason they closely resemble terrestrial igneous rocks. Classification HED meteorites are broadly divided into: * Howardites * Eucrites * Diogenites Several subgroups of both eucrites and diogenites have been found. The HED meteorites account for about 5% of all falls, which is about 60% of all achondrites. Origin No matter their composition all these types of meteorite are thought to have originated in the crust of the asteroid Vesta. According to this theory the differences of composition are due to their ejection at different moments in the geologic history of Vesta. Their crystallization ages have been determined to be between 4.43 and 4.55 billion years from radioisotope ratios. HED meteorit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V-type Asteroid
A V-type asteroid or Vestoid is an asteroid whose spectral type is that of 4 Vesta. Approximately 6% of main-belt asteroids are vestoids, with Vesta being by far the largest of them. They are relatively bright, and rather similar to the more common S-type asteroid, which are also made up of stony irons and ordinary chondrites, with V-types containing more pyroxene than S-types. A large proportion of vestoids have orbital elements similar to those of Vesta, either close enough to be part of the Vesta family, or having similar eccentricities and inclinations but with a semi-major axis lying between about 2.18 AU and the 3:1 Kirkwood gap at 2.50 AU. This suggests that they originated as fragments of Vesta's crust. There seem to be two populations of Vestoids, one created 2 billion years ago and the other 1 billion years ago, coming respectively from the enormous southern-hemisphere craters Veneneia and Rheasilvia. Fragments that ended up in the 3:1 Jupiter resonance were perturbed o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vesta Family
The Vesta family (adj. ''Vestian''; ) is a family of asteroids. The cratering family is located in the inner asteroid belt in the vicinity of its namesake and principal body, 4 Vesta. It is one of the largest asteroid families with more than 15,000 known members and consists of mostly bright V-type asteroids, so-called "vestoids". Characteristics The Vestian asteroids consist of 4 Vesta, the second-most-massive of all asteroids (mean diameter of 530 km), and many small asteroids below 10 km diameter. The brightest of these, 1929 Kollaa and 2045 Peking, have an absolute magnitude of 12.2, which would give them a radius of about 7.5 km assuming the same high albedo as 4 Vesta. The family originated from an impact on asteroid 4 Vesta, with the giant south-polar crater the likely impact site. The family are thought to be the source of the HED meteorites. The Vesta family also includes a few J-type asteroids (related to the V-type), which are thought to have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
