Howardite

Howardite
— Group —

QUE94200, a Howardite about 5 centimetres (2.0 in) across, found in the Queen Alexandra Range in Antarctica.
Compositional type Stony
Type Achondrite
Class Asteroidal achondrite
Clan HED meteorite
Parent body 4 Vesta
Total known specimens ~200

Howardites are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta, and as such are part of the HED meteorite clan.[1][2] There are about 200 distinct members known.[3]

Characteristics

They are a regolith breccia consisting mostly of eucrite and diogenite fragments, although carbonaceous chondrules and impact melt can also occur. The rock formed from impact ejecta which was later buried by newer impacts and lithified due to the pressure from overlying layers. Regolith breccias are not found on Earth due to a lack of regolith on bodies which have an atmosphere.

Name

Howardites are named for Edward Howard, a pioneer of meteoritics. An arbitrary divide between howardites and the polymict eucrites is a 9:1 ratio of eucrite to diogenite fragments.

See also

References

  1. ↑ Harry Y. McSween, Meteorites and their parent planets. Cambridge University Press, 1999. ISBN 0-521-58751-4, ISBN 978-0-521-58751-8. - p.129
  2. ↑ Howardite - daviddarling.info
  3. ↑ Meteoritical Bulletin Database: Howardites

External links

This article is issued from Wikipedia - version of the 11/8/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.