| 词条 | Angrite |
| 释义 |
|Subdivision = Group |Name = Angrite |Alternative_names = |Image = NWA 2999 meteorite, angrite.jpg |Image_caption = A slice of "NWA 2999". Note the similarity to a terrestrial basalt. |Image_alt_text = |Compositional_type = Stony meteorite |Type = Achondrite |Class = |Clan = |Structural_classification = |Parent_body = Possibly 289 Nenetta, 3819 Robinson or Mercury |Composition = |Petrologic_type = |Number_of_specimens = 12 |TKW = |Image2 = |Image2_caption = |Image2_alt_text = }} Angrites are a rare group of achondrites consisting mostly of the mineral augite with some olivine, anorthite and troilite. The group is named for the Angra dos Reis meteorite. Angrites are basaltic rocks, often having porosity, with vesicle diameters of up to {{convert|2.5|cm}}. They are the oldest igneous rocks, with crystallization ages of around 4.55 billion years. OriginBy comparing the reflectance spectra of the angrites to that of several main belt asteroids, two potential parent bodies have been identified: 289 Nenetta and 3819 Robinson. Other scientists have suggested that angrites could represent ejecta from Mercury. Notable meteoritesThere are currently 12 meteorites classified as angrites. The type specimen, the Angra dos Reis meteorite, was an observed fall in 1869 and at {{convert|1.5|kg}} is the fourth-heaviest angrite. The three largest are D'Orbigny ({{convert|16.55|kg}}), "Sahara 99555" ({{convert|2.71|kg}}) and "NWA 4931" with {{convert|2.14|kg}}.[1] See also
External links
References1. ^{{cite web|title=Meteoriticial Society Database|url=http://www.lpi.usra.edu/meteor/metbull.php|publisher=Meteoritical Society|accessdate=2 January 2013}} {{Meteorites}} 1 : Asteroidal achondrites |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。