Burnwell meteorite, Pike County, Kentucky, USAi

Regional Level Types
Burnwell meteorite	Meteorite Fall Location
Pike County	County
Kentucky	State
USA	Country

Fell 4 Sept 1990
Ordinary Chondrite, high-iron (H4-an; S3)
1504 grams, single stone

The Burnwell stony meteorite fell with a whirring sound which was followed by a sharp impact as the stone penetrated a porch rooftop and its floor, frightening a nearby goat and horse. However, the meteorite itself, almost completely covered by a fusion crust, was not discovered until the next day. The meteorite turned out to be a nearly 'ordinary' H4 chondrite (mildly metamorphosed, relatively high in iron). Pyroxene, olivine, Fe-Ni metal with minor troilite predominate in the chondrules and groundmass. But Burnwell is only 'nearly' a standard H4 chondrite. The composition of various components of the meteorite — Olivine (Fa15.8), pyroxene (Fs13.4), Co abundance in Fe-Ni metal, and Oxygen isotopes — are just outside the range of all or almost all H Chondrites. Besides the various small chemical anomalies, Burnwell has a more reduced overall mineralogical assemblage than other H Chondrites. It has also experienced significant shock (S3 level) which also complicates any interpretation.

The presence of these small, but real differences in Burnside is part of the continuing problematics of meteorite classification. Are these small anomalies due to the fact that our H4 meteorite collection represents a biased sample of the H4 parent body or does Burnwell represent a fragment from another asteroid with a similar, but not identical composition?? There have been 361 witnessed falls of H chondrites as of early October 2014. Over 19,000 finds are also listed at the Meteoritical Society's Meteoritical Bulletin. [Many of the 19,000 finds are quite small, too small to properly categorize at this level of detail — but several thousand have been categorized and characterized.] At the present time only Burnwell and 3 or 4 other finds are clear outliers. At this point, personal taste comes into play — when doing science it is usually helpful to try to establish a record with as few hypothesis as possible — and so, it would clearly be simpler if the 'ordinary' chondrites were samples of — at most — 3 original parent bodies (OPB). We would like to believe that there was a single H-chondrite OPB, a single L-chondrite OPB and a single LL-chondrite OPB. Some have suggested that the L-chondrites and a single LL-chondrites come from a single OPB. Whether these preferred suppositions are actually true, however, is a different question. Burnwell may or may not come from another parent asteroid. In time, perhaps, more facts will be sufficient to resolve this particular issue to the satisfaction of the scientific community. Keep posted.

Other Regions, Features and Areas containing this locality

References