Muonionalusta End Piece

A ONE MILLION YEAR RESIDENT OF EARTH

Of all the meteorites ever found, Muonionalusta is the one with the longest tenure here on Earth, having fallen between 800,000 and 1,200,000 years ago. It was found in 1906 outside the town of Kitkiöjärvi in Northern Sweden, close to the Finnish border and west of the Finnish municipality of Muonio (hence the name Muonionalusta, or "downstream from Muonio"). Having fallen well before humans appeared on the scene, in an area still sparsely populated, it is not surprising that it was not found until the beginning of the 20th century.

The cut side of this substantial end piece has been etched and polished to reveal the beauty of Muonionalusta’s crystalline structure. In addition, the uncut exterior of this end piece also shows the meteorite's crystalline structure in 3-dimensional form, a extremely rare occurrence not normally seen on iron meteorites, and a function of the nearly one million years of terrestrial weathering this meteorite has experienced, mimicking the etching process that is often necessary to produce these lines on the cut face of an iron meteorite.

As extended cooling for millions of years is required for the molecules of the two major iron-nickel alloys of iron meteorites — kamacite and taenite — to crystallize, the pattern seen here is diagnostic in the identification of iron meteorites. These patterns are referred to as Widmanstätten patterns in honor of Count Alois von Beckh Widmanstätten, the director of the Imperial Porcelain Works in Vienna in the early 19th century, who happened to notice them as he was investigating the structure of iron meteorites. While working in Italy, researcher William Thompson also noticed this pattern and wrote a scientific paper about them four years before the Count’s observation. However, the Napoleonic Wars and instability in southern Italy at the time made it extremely challenging to be contact with his colleagues in England and his findings were not published in English until years later. There has been a recent effort to honor Thompson with what was his indeed his discovery by referring to such patterns as Thompson structures. Regardless of what they are called, the pattern seen in the meteorite offered here is robust, although there are some rare slips (or, "glide-plane displacements") in the pattern, caused by a large object impacting Muonionalusta's parent asteroid while flying in space, disrupting the pattern's continuous growth.

REFERENCES:

Meteoritical Bulletin Entry for Muonionalusta