Polymict eucrite
A polymict eucrite is a breccia of different eucrite rocks with less than 10 per cent diogenite.
A polymict eucrite is a breccia containing fragments of various eucrites and only a small amount of diogenite, conventionally less than about 10 per cent by volume. If more diogenite is present, the rock is called a howardite instead.
This boundary is a convenient but somewhat arbitrary division of a continuum. On Vesta's surface, impacts mixed rocks from basaltic flows, cumulate layers and deeper diogenite zones. Where little diogenite was excavated, polymict eucrites formed; where more deep material was mixed in, howardites resulted. The proportions help researchers infer where on Vesta, or how deeply excavated, a sample came from.
Polymict eucrites are rewarding to study because each clast can be analysed separately. Some contain fragments of impact melt, carbonaceous chondrite and unusual basalts not found as single meteorites. Together with howardites, they act as natural samplers of Vesta's surface, much like a soil sample on Earth combines rocks from a whole hillside.
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