At the time of its discovery the meteorite was apparently a single, large, cohesive egg-shaped mass. However, upon its removal in 1928 it broke to pieces. This is somewhat surprising since, although the Winona meteorite is fragile, it had evidently survived its passage through the atmosphere intact and been moved by the pueblo-builders to the burial site where it lay undisturbed for over 700 years.
Winonaites are composed largely of fine-grained pyroxenes, with some magnesium-rich olivine, troilite (iron sulfide), and nickel-iron metal. They strongly resemble in compositions the silicate inclusions in type IAB iron meteorites. This similarity suggests that winonaites and IAB group irons may have come from the same parent body – a partially differentiated asteroid that suffered a catastrophic impact just as it was starting to form an iron core and a silicate-rich crust. According to this idea, the impact mixed silicates into molten nickel-iron forming the IAB irons, and mixed olivine-rich residues of partial melts into unmelted silicates, forming the winonaites.
Related category METEORS AND METEORITES
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