Ruqayyah Snyder
Meteorites are solid bodies that have fallen to Earth from space without being completely vapourised by their passage through the atmosphere. They are mostly fragments of asteroids and consist of primitive solid matter similar to that from which Earth was formed. Meteorites are traditionally named after the location where they are found. There have been 756 meteorites from Australia listed in the Meteoritical Bulletin Database of the Meteoritical Society. The Wolf Creek Crater in Western Australia is perhaps the best-known crater in the country, believed to have been formed by a meteorite around 300,000 years ago. The Desert Fireball Network, a project that started in 2012, has installed a network of 32 automated observatories in remote areas of Australia to track meteorites.
| Characteristics | Values |
|---|---|
| General classes of meteorites | Stony, Iron, Stony-iron |
| Most abundant type of meteorite | Stony |
| Type of meteorite that is commonly found | Iron |
| Origin of meteorites | Solar System |
| Formation age of meteorites | Around 4.56 billion years |
| Size of meteorites | Range from pea-sized to several tonnes |
| Example of a famous meteorite fall in Australia | Murchison, near Shepparton, Victoria |
| Best-known crater in Australia | Wolf Creek Crater in Western Australia |
| Number of distinct meteorites known from Australia | 756 |
| Number of meteorite specimens in the Western Australian Museum | 14,000 |
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What You'll Learn
Know what to look for
Meteorites are solid bodies that have fallen to Earth from interplanetary space. They are typically fragments of asteroids and consist of primitive solid matter similar to that from which Earth was originally formed. Meteorites come in three general classes: stony meteorites, iron meteorites, and stony-iron meteorites. Stony meteorites are the most abundant, but iron meteorites are the ones most commonly found as they are more easily recognised and weather less readily when lying on the ground. Irons are the second most common type of meteorite and have the largest masses, such as the 12-tonne 'Mundrabilla' found in Western Australia. Stony-iron meteorites are the least common.
Meteorites vary in size, ranging from pea-sized pieces to large masses of several tonnes. They can sometimes break up into several pieces while in flight or when they hit the Earth. When a small meteorite hits the ground, a pit is formed at the point of impact in soft ground, with a diameter similar to that of the meteorite. Larger meteorites tend to break up on impact, creating a fragmentation crater.
Stones are the most common type of meteorite and can be of moderately large mass. They consist mainly of the silicate minerals olivine and pyroxene, with feldspar and scattered nickel-iron. Stones are further subdivided into chondrites and achondrites, depending on the presence or absence of small, spherical, concretionary mineral structures (chondrules). Most stones are chondrites, of which an unusual type is the carbonaceous chondrite, which has a high organic content and amino acid-like chemicals.
Iron meteorites are the second most common type and have the largest masses. They are made of dense silvery nickel-iron metal alloys (taenite and kamacite) and have a range of nickel contents. When cut, polished, and etched with an acid/alcohol solution, some iron meteorites show a characteristic criss-cross pattern of intersecting platy nickel-iron crystals known as the Widmanstatten structure.
Stony-iron meteorites are the least common type. One type, the Pallasite Class, has roughly equal amounts of the silicate mineral olivine and nickel-iron metal. Another type, the Mesosiderite Class, is a broken-up mixture of pyroxene with nickel-iron.
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Look in the Nullarbor region of Western Australia
Meteorites are solid bodies that have fallen to Earth from interplanetary space. They are traditionally named after the location where they are found.
The Nullarbor region of Western Australia is a treeless, limestone desert that is part of the larger Eucla Basin, which straddles the border between Western Australia and South Australia. The semi-arid to arid climate of the Nullarbor is ideal for preserving meteorites. The lack of vegetation and pale limestone country rock also make the Nullarbor a great spotting ground for meteorites.
Dating of the age of fall of Nullarbor stony meteorites indicates that meteorites have been accumulating there for at least 35,000 years. To date, thousands of specimens from more than 330 distinct meteorites have been described from the whole Nullarbor Region.
The Mundrabilla meteorite, one of the largest meteorites found, was discovered in the Nullarbor region in 1911. It had a total known weight of 22 tonnes, with the main mass (the single largest fragment) accounting for 12.4 tonnes. The Mundrabilla meteorite is now conserved at the Western Australia Museum.
In addition to the Mundrabilla meteorite, several other meteorites have been found in the Nullarbor region, including the Premier Downs I, II, and III, as well as the Loongana Station West meteorite.
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Look for black rocks in Antarctica
Meteorites are solid bodies that have fallen to Earth from interplanetary space. They are traditionally named after the location where they are found. Meteorites vary in size, from small pebbles to single objects or groups of many tonnes. Stony meteorites are the most common, but iron meteorites are the ones most commonly found as they are more easily recognised and weather less readily. Irons are the second most common type of meteorite and have the largest masses, such as the 12-tonne 'Mundrabilla' in Western Australia.
If you're looking for meteorites in Australia, a good place to start is the Western Australian Museum, which has an internationally recognised meteorite collection of around 14,000 specimens from 750 distinct meteorites. The Nullarbor region in south-east Western Australia has also yielded around 500 meteorites, which may double the number of distinct meteorites known from Australia.
However, if you're specifically interested in finding a meteorite in Antarctica, there's a good reason to look for black rocks. Antarctica is a prime location for meteorite hunting because black rocks are easily spotted against the white ice, and they are almost guaranteed to be meteorites. So, if you're planning a trip to Antarctica, keep your eyes peeled for black rocks among the ice!
It's important to note that while meteorites are rare, it's not impossible to find one. In addition to their black colour, meteorites can be identified by their composition. They often contain minor minerals that are not present on Earth, and they may have a characteristic criss-cross pattern of intersecting platy nickel-iron crystals known as a Widmanstatten structure. So, if you come across a black rock in Antarctica, be sure to examine its composition to confirm if it's a meteorite.
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Search for pallasite or stony-iron meteorites
Stony-iron meteorites are the least common type of meteorite. They consist of almost equal parts iron-nickel metal and silicate minerals, including precious and semi-precious gemstones. Pallasites, a type of stony-iron meteorite, are believed to form between the silicate mantle (outer shell) and the molten metal core of a differentiated asteroid. The primary silicate mineral in pallasites is olivine, distinguishable by its greenish hue. The olivine crystals found in the Marjalahti pallasite are of such high purity that they were adopted as a scientific standard for olivine composition.
Pallasites contain large, olive-green crystals, a form of magnesium-iron silicate called olivine, embedded entirely in metal. Sometimes, the olivine occurs in clusters or vein patterns through solid metal. The scientific community has not yet reached a consensus on how pallasites formed. Some scientists believe they formed in melted asteroids similarly to iron meteorites, with dense iron metal sinking towards the centre to form an iron core. Pallasites are thought to be samples of the boundaries between a metal core and the silicate, olivine-rich mantle around it.
The Huckitta meteorite, found in the Northern Territory, is the world's largest single stony-iron pallasite, weighing 1.4 tonnes. The Australasian strewn field encompasses most of Southeast Asia, including western and southern Australia. This field is believed to be the source of tektites found in the region. Tektites are the solidified splashes of molten rock ejected by the impact of very large, high-velocity meteorites.
When searching for meteorites, it is important to look out for pits or craters formed by the impact of meteorites. Smaller meteorites (up to about 1 tonne) create a hole or pit at the point of impact in soft ground, with a diameter similar to that of the meteorite. Larger meteorites tend to break up on impact, creating fragmentation craters with scattered fragments of the meteorite, soil, and rock. Wolf Creek Crater in Western Australia and Gosses Bluff in the Northern Territory are examples of impact craters in Australia.
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Visit the Western Australian Museum
If you're interested in meteorites and happen to be in Australia, a visit to the Western Australian Museum is a must. The museum's meteorite collection is internationally recognised as one of the most significant in the southern hemisphere. With around 14,000 specimens from over 750 distinct meteorites, it's a comprehensive collection that represents most of the known groups of meteorites, as well as some unique and anomalous ones. The museum's collection includes meteorites from the Moon and Mars, as well as classic 19th-century examples.
The Western Australian Museum's collection showcases meteorites of various types, including stony meteorites, iron meteorites, and stony-iron meteorites. Irons, or iron meteorites, are the second most common type, often consisting of dense silvery nickel-iron metal alloys. The Mundrabilla meteorite, weighing in at 12 tonnes, is a notable example in this category. Stony meteorites, primarily composed of silica minerals, are the most abundant type, and the carbonaceous chondrites, such as the Murchison meteorite from Victoria, are of particular interest due to their distinct characteristics. Stony-iron meteorites, a combination of the previous two types, are the least common, with the Huckitta meteorite from the Northern Territory being a notable example.
The history of the museum's meteorite collection is fascinating. The earliest acquisitions were obtained under Thomas Cooksey, Curator of Minerals, in the late 19th century. Notable additions include the Nocoleche iron meteorite, the Youndegin iron meteorite, and the Thunda iron meteorite. The museum continued to expand its collection over the years, acquiring meteorites from other organisations and receiving specimens from finders. The Western Australian Museum also has a vast collection of plaster meteorite replicas, cast from both Australian and international originals, providing a comprehensive overview of the different types of meteorites.
A visit to the Western Australian Museum promises an insightful journey into the world of meteorites. With its diverse and extensive collection, the museum offers a unique opportunity to learn about the different types of meteorites, their origins within the Solar System, and their scientific significance. The specimens on display, ranging from meteoritic dust to large masses like the Mundrabilla meteorite, provide a tangible connection to the mysteries of our universe. So, whether you're a space enthusiast or simply curious, a visit to the Western Australian Museum is definitely worth considering during your stay in Australia.
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