The H type ordinary chondrites are the most common type of meteorite, accounting for approximately 40% of all those catalogued, 46% of the ordinary chondrites, and 44% of all chondrites.[1] The ordinary chondrites are thought to have originated from three parent asteroids, whose fragments make up the H chondrite, L chondrite and LL chondrite groups respectively.[2]
| H chondrite | |
|---|---|
| — Group — | |
 Weston meteorite, H4 | |
| Type | Chondrite |
| Structural classification | ? |
| Class | Ordinary chondrite |
| Subgroups |
|
| Parent body | Possibly 6 Hebe, less likely 3 Juno & 7 Iris |
| Composition | Iron ~25–31%, bronzite (an orthopyroxene), olivine (with characteristic fayalite (Fa) content 16 to 20 mol%), nickel-iron 15–19%, troilite 5% |
| Petrologic type | 3 (~2.5%), 5 (40%), 4 & 6 (57.5%) |
| Alternative names | Bronzite chondrites, Olivine bronzite chondrites |
 Nuevo Mercurio, H5 | |
Name
editThe name comes from their High iron abundance, with respect to other ordinary chondrites.
Historically, the H chondrites have been named bronzite chondrites or olivine bronzite chondrites for the dominant minerals, but these terms are now obsolete.
Parent body
editA probable parent body for this group is the S-type asteroid 6 Hebe, with less likely candidates being 3 Juno and 7 Iris.[3] It is supposed that these meteorites arise from impacts onto small near-Earth asteroids broken off from 6 Hebe in the past, rather than originating from 6 Hebe directly.
The H chondrites have very similar trace element abundances and Oxygen isotope ratios to the IIE iron meteorites, making it likely that they both originate from the same parent body.
Iron
editTheir high iron abundance is about 25–31% by weight. Over half of this is present in metallic form, making these meteorites strongly magnetic despite the stony chondritic appearance.
Mineralogy
editThe most abundant minerals are bronzite (an orthopyroxene), and olivine. Characteristic is the fayalite (Fa) content of the olivine of 16 to 20 mol%. They contain also 15–19% of nickel-iron metal and about 5% of troilite. The majority of these meteorites have been significantly metamorphosed, with over 40% being in petrologic class 5, most of the rest in classes 4 and 6. Only a few (about 2.5%) are of the largely unaltered petrologic class 3.
Gallery
edit-
Gao-Guenie, H5 -
H5 Dar Bou Nali South Morocco
See also
editReferences
edit- ^ "Natural History Museum, meteorite catalogue". Archived from the original on 2006-05-03. Retrieved 2005-11-29.
- ^ NASA (YouTube) – Dr. David Kring – Asteroid Initiative Workshop Cosmic Explorations Speakers Session
- ^ M. J. Gaffey & S. L. Gilbert Asteroid 6 Hebe: The probable parent body of the H-Type ordinary chondrites and the IIE iron meteorites, Meteoritics & Planetary Science, Vol. 33, p. 1281 (1998).
External links
edit- The Catalogue of Meteorites Archived 2006-05-03 at the Wayback Machine