Pasamonte meteorite, Union County, New Mexico, USAi

Regional Level Types
Pasamonte meteorite	Meteorite Fall Location
Union County	County
New Mexico	State
USA	Country

Fall, 24 March 1933; 5.1 kg; Spectacular bolide
Eucrite, polymict w. anomalous O-isotopes


Traveling at a low entry angle, a spectacular bolide was seen over a 500 km range in several states, its detonations were heard and felt for 150 km, and it then broke up at ~ 30 km altitude — leaving a cloud of dust in its wake. A large number of small stones were strewn over a length of ~40 km - often with nice fusion crusts over some or all of their surfaces. Except for its unusually friable texture, over the past few decades the Pasamonte meteorite has not seemed that different from most eucrites. First impressions can be expressed in quite conventional terms. Over 90% of this ancient meteorite is composed of a two-to-one pyroxene-plagioclase intergrowth of eucritic fragments. Pyroxene (mostly pigeonite) and plagioclase (mostly bytownite) fragments are variable and sometimes zoned as are many eucritic breccias. However, the number of reported minor phases (silicates, phosphates, opaques, etc.) is somewhat larger than usual for eucrites and a number of geochemical peculiarities have been noted. And, finally, in the past decade it has been reported and now confirmed (see references) that Pasamonte's oxygen-isotopes do not conform to the usual patterns observed — and now expected — for eucrites and the related howardites and diogenites (HED achondrites).

An impressive amount of information from HED meteorites, astronomical studies of Vestoids (asteroidal fragments of Vesta), and the Dawn spacecraft mission to Vesta has made it compellingly clear to most informed observers that Vesta is indeed the parent body of most eucrites and other HED meteorites. However, some of this information is also beginning to make it just as clear that a few of our 'eucrites' and 'howardites' are fragments from other ancient and moderately large, differentiated asteroids which seem to have disappeared from 'center stage.'

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References