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The layers of the Earth, a differentiated planetary body. In planetary science, planetary differentiation is the process by which the chemical elements of a planetary body accumulate in different areas of that body, due to their physical or chemical behavior (e.g. density and chemical affinities).
The classification scheme uses the letter "I" for "inconsistent" spectral data, and should not be confused with a spectral type. An example is the Themistian asteroid 515 Athalia, which, at the time of classification was inconsistent, as the body's spectrum and albedo was that of a stony and carbonaceous asteroid, respectively. [8]
Thought to be the largest undifferentiated asteroid, 10 Hygiea seems to have a uniformly primitive composition of carbonaceous chondrite, but it may actually be a differentiated asteroid that was globally disrupted by an impact and then reassembled. Other asteroids appear to be the remnant cores or mantles of proto-planets, high in rock and metal.
Vesta (radius 262.7 ± 0.1 km), the second-largest asteroid, appears to have a differentiated interior and therefore likely was once a dwarf planet, but it is no longer very round today. [74] Pallas (radius 255.5 ± 2 km ), the third-largest asteroid, appears never to have completed differentiation and likewise has an irregular shape.
For the purposes of this article, "asteroid" refers to minor planets out to the orbit of Neptune, and includes the dwarf planet Ceres, the Jupiter trojans and the centaurs, but not trans-Neptunian objects (objects in the Kuiper belt, scattered disc or inner Oort cloud). For a complete list of minor planets in numerical order, see List of minor ...
A prominent example is 1 Ceres, the largest asteroid, which is an interloper in the family once named after it (the Ceres family, now the Gefion family). Spectral characteristics can also be used to determine the membership (or otherwise) of asteroids in the outer regions of a family, as has been used e.g. for the Vesta family , whose members ...
Similar differentiation processes are believed to have occurred on some of the large moons and dwarf planets, [32] though the process may not always have been completed: Ceres, Callisto, and Titan appear to be incompletely differentiated. [114] [115] The asteroid Vesta, though not a dwarf planet because it was battered by impacts out of ...
In this list the periods are sourced from the Light Curve Data Base (LCDB), [2] and are given in both seconds and hours. Most minor planets have rotation periods between 2 and 20 hours. [ 1 ] [ 3 ] As of 2019 [update] , a group of 887 bodies – most of them are stony near-Earth asteroids with small diameters of barely 1 kilometre – have an ...