Angrite
— Group —
A slice of "NWA 2999". Note the similarity to a terrestrial basalt.
Compositional typeStony meteorite
TypeAchondrite
Parent bodyPossibly 289 Nenetta, 3819 Robinson or Mercury
Total known specimens12

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 2.5 centimetres (0.98 in).

They are the oldest igneous rocks, with crystallization ages of around 4.55 billion years.

Origin

By 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, however later work has cast significant doubt upon these claims.[1]

Notable meteorites

There are currently 12 meteorites classified as angrites. The type specimen, the Angra dos Reis meteorite, was an observed fall in 1869 and weighed 1.5 kilograms (3.3 lb). Most of it has been lost over time; the largest remaining piece, weighing 101 grams, is kept at the Museum of Natural History in Rio de Janeiro.[2]

See also

References

  1. ^ Irving, A. J.; Kuehner, S. M.; Rumble, D.; Bunch, T. E.; Wittke, J. H. (December 2005). "Unique Angrite NWA 2999: The Case For Samples From Mercury". American Geophysical Union, Fall Meeting 2005, abstract (2005): P51A-0898. Bibcode:2005AGUFM.P51A0898I.
  2. ^ Grady, Monica M. (2000). Catalogue of Meteorites, 5th Edition. London: Cambridge University Press. p. 74. ISBN 978-0521663038.