Mundrabilla iron meteorite

Many meteorites have been found on the Nullarbor Plain, as it is easier to find them in flat country where there is poor vegetation cover. The dry climate also helps to preserve them as they don’t rust away. There are many large and small masses of the Mundrabilla meteorite, as it broke up on entry through Earth’s atmosphere. The largest mass found was 12.4 tonnes and is currently held at the Western Australian Museum.

The meteorite is a nickel-iron type, classified as a medium octahedrite, with nickel content of 7.8 per cent. Most meteorites come from the Asteroid Belt, about 400 million km out from the Sun. Iron meteorites such as Mundrabilla are thought to have been originally part of the metallic core of an asteroid, broken up through collisions in the Asteroid Belt. Most meteorites are as old as our solar system, about 4.6 billion years.

The first piece of Mundrabilla was found in 1911 and weighed 112 g. Between 1911 and 1965, seven pieces weighing between 39 g and 116 g were found but, in 1966, two large masses of 12.4 tonnes and 5.44 tonnes were found during a geological survey, lying 180 m apart. In 1979, two further masses of 800 kg and 840 kg were found 20 km east of where the two large masses were found. A further 2.5 tonne mass was also found and is now held at the South Australian Museum.

Other sizeable masses have been occasionally found, including this 617 kg piece, found 13 km west of the main mass in the late 1970s. Its surface is pitted with shallow hollows called ‘regmaglypts’ which form when heat from friction due to its fiery passage through Earth’s atmosphere scooped out and vaporised parts of its surface. If added up, all the pieces found so far total 24 tonnes, and all were part of the same meteorite shower. This specimen was acquired through a Western Australian donor under the former Taxation Incentives for the Arts Scheme.