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E-type asteroid
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{{Short description|Asteroid spectral type}} [[File:2867 Šteins by Rosetta (reprocessed).png|thumb|right|E-Type asteroid [[2867 Šteins]]]] '''E-type''' (enstatite achondrite–type) asteroids are [[asteroid]]s thought to have [[enstatite]] (MgSiO<sub>3</sub>) [[achondrite]] surfaces. They form a large proportion of asteroids inward of the [[asteroid belt]] known as [[Hungaria asteroids]],<ref name="isbn0-521-58751-4">{{cite book |author=McSween, Harry Y. |title=Meteorites and their parent planets |publisher=[[Cambridge University Press]] |location=Cambridge, UK |year=1999 |pages= 168|isbn=978-0-521-58751-8 |url=https://books.google.com/books?id=BtNJoP5HlU8C&dq=%22E-type+asteroid%22+%22Hungaria+asteroids%22&pg=PA168 }}</ref> but rapidly become very rare as the asteroid belt proper is entered. Some are quite far from the inner edge of the asteroid belt, such as [[64 Angelina]]. They are thought to have originated from the highly reduced mantle of a differentiated asteroid. ==Description== E-type asteroids have a high [[albedo]] (0.3 or higher), which distinguishes them from the more common [[M-type asteroid|M-type]] [[asteroid]]s. Their [[electromagnetic spectrum|spectrum]] is featureless flat to reddish. Probably because they originated from the edge of a larger parent body rather than a core, E-types are all small, with only three ([[44 Nysa]], [[55 Pandora]], [[64 Angelina]]) having diameters above 50 kilometres and no others above 25 kilometers (the biggest three also orbit atypically far, c. 3 AU, from the Sun). [[Aubrite]]s (enstatite achondrite meteorites) are believed to come from E-type asteroids,<ref>{{cite journal |last=Zellner |first=B. |display-authors=etal |year=1977 |title=The E asteroids and the origin of enstatite achondrites |journal=Geochim. Cosmochim. Acta |volume=41 |pages=1759–67 |doi=10.1016/0016-7037(77)90208-3|bibcode = 1977GeCoA..41.1759Z |issue=12 }}</ref> because Aubrites could be linked to the E-type asteroid [[3103 Eger]].<ref>{{cite journal|last1=Gaffey|first1=Michael J.|last2=Reed|first2=Kevin L.|last3=Kelley|first3=Michael S.|title=Relationship of E-type Apollo asteroid 3103 (1982 BB) to the enstatite achondrite meteorites and the Hungaria asteroids|journal=Icarus|date=November 1992|volume=100|issue=1|pages=95–109|doi=10.1016/0019-1035(92)90021-X|bibcode = 1992Icar..100...95G }}</ref> This grouping may be related to the [[X-type asteroid|Xe-type]] of the [[asteroid spectral types#SMASS classification|SMASS classification]]. ==E-Belt== {{main|E-belt asteroids}} The E-type asteroids of the Hungaria family are thought to be the remains of the hypothetical [[E-belt asteroids|E-belt asteroid population]].<ref>[https://www.youtube.com/watch?v=4MMYTzb0L_s&index=111&list=PL7B4FE6C62DCB34E1 Late, Late Heavy Bombardment - Bill Bottke] (SETI Talks) – Youtube.com</ref> The dispersal of most of that hypothetical E-Belt might have been caused by the [[Planetary migration|outward migration]] of the [[gas giant]]s of the [[Solar System]] according to simulations done under the [[Nice model]] – and these dispersed E-Belt asteroids might in turn have been the impactors of the [[Late Heavy Bombardment]]. ==Exploration== On September 5, 2008, ESA's robotic spaceprobe [[Rosetta (spacecraft)|Rosetta]] visited the E-type asteroid [[2867 Šteins]].<ref name=keller>[http://www.sciencemag.org/cgi/content/abstract/327/5962/190 H. U. Keller, et al. - '''E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board Rosetta''' - Science 8 January 2010: Vol. 327. no. 5962, pp. 190 - 193 ] {{doi|10.1126/science.1179559}}</ref> Spectral data from the spacecraft confirmed the asteroid was composed mainly of iron-poor minerals such as [[enstatite]] (magnesium-rich pyroxene), [[forsterite]] (magnesium-rich olivine) and [[feldspar]]. ==See also== *[[Asteroid spectral types]] *[[L-type asteroid]] *[[S-type asteroid]] *[[X-type asteroid]] *[[2867 Šteins]] ==References== {{reflist}} {{Asteroids}} {{Small Solar System bodies}} {{More citations needed|date=September 2008}} [[Category:Asteroid spectral classes]] [[Category:E-type asteroids (Tholen)|*]]
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