Meteorite Muonionalusta – Norrbotten, Sweden

The Muonionalusta meteorite fell to Earth an estimated one million years BC, making it one of the oldest known meteorite impacts. It comes from the asteroid belt between Mars and Jupiter and is estimated to be more than 4.5 billion years old. This belt is an area where a large number of asteroids and meteorites are found, sometimes breaking off and travelling through space before eventually landing on Earth. Muonionalusta is therefore a fragment of one of these asteroids that survived its passage through the atmosphere and hit the Earth's surface.

It is classified as a fine Type IVA octahedrite and is known primarily for its beautiful Widmanstätten patterns, which are the disordered structures of the iron-nickel crystals that make up the meteorite. These patterns are formed by the slow cooling of the metal in space, but not all iron meteorites have these patterns. To see these patterns, the surface of the meteorite must be polished and then etched with dilute nitric acid, preferably with methanol.

The first fragment of the Muonionalusta meteorite was discovered in 1906, and others have been found throughout the 20th and 21st centuries, some of which weigh up to several hundred kilograms. It consists of approximately 91% iron, 8.4% nickel, trace amounts of rare elements such as gallium, germanium and iridium, and various minerals.