Australites are tektites found in Australia. They are mostly dark or black, and have shapes including discs and bowls that are not seen in other tektites. NASA used the shape of "flanged button" australites in designing re-entry modules for the Apollo program in the 1960s. [1]
Indigenous Australians termed australites ooga ("staring eyes"), and they were used as sacred objects or as cutting tools. [2] Europeans found out about australites in 1857, when explorer Thomas Mitchell gave naturalist Charles Darwin a mysteriously shaped piece of natural black glass. Darwin thought that australites were of volcanic origin due to their similarity to obsidian, volcanic glass. [1] [2] [3] Later, australites were called blackfellows' buttons and obsidian bombs.[ citation needed ]
One of the first scientists to seriously study australites was Charles Fenner, who saw his first australite in 1907. He believed that australites were glass meteorites. [4]
Early theories about the source of australites included volcanoes, the bushfires that are common in Australia, or fusion of sand by lightning (fulgurites). Some scientists believed them to be meteorites, possibly lunar meteorites ejected from the Moon in impacts (now disproved due to the different composition of lunar rocks). [1]
Although different theories about the origin of australites are still circulating, most scientists believe that australites formed during a large asteroid or comet impact on the Earth. The impact ejected myriad small rocks right out of the atmosphere. The australites acquired their streamlined, aerodynamic forms when they re-entered the Earth's atmosphere while molten and travelling at high velocities. [1]
Most australites are found in Southern Australia, below 25 degrees latitude. [5] Based on similar ages [6] and compositions, [7] they represent the southern edge of the vast Australasian tektite strewnfield that stretches from southern China to Australia. The Australasian strewnfield has an age of 610,000 to 750,000 years and may be the result of an impact in Indochina. [5]
The primary forms of australites are sphere, oval, boat, dumbbell and teardrop. Australites are smaller than other tektites and different in shape. Their initial velocity was higher than other tektites: enough to propel them just out of the Earth's atmosphere, so they then re-entered the atmosphere and underwent a rare secondary melting. [8]
One of the most famous australite shapes is the "flanged button". Flanged buttons are rare, but the most unusual and rarest australites are discs, bowls, plates and other small forms (mini tektites). They are very thin. George Baker called them "flying flanges", the result of distortion of "initially small primary forms by aerodynamic frictional heating". He wrote:
These are all very special forms of tektites not encountered among the other known tektite-strewn fields of the world, the rarity and unexcelled character of these well-preserved, complete to nearly complete, unique types of tektites cannot be overstressed. [9]
Well preserved shapes are found near Port Campbell in western Victoria.
Chapman and Larson experimented on the ablation of australites. At first they seemed to prove their extraterrestrial origin, but later in repeated studies they claimed that the australites could not have come from outside the Earth-Moon system. They were able to reproduce the shapes, flanges and the peculiar network of the rings on the front face in great detail. [10]
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star or falling star; astronomers call the brightest examples "bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater.
Meteor Crater, or Barringer Crater, is a meteorite impact crater about 37 mi (60 km) east of Flagstaff and 18 mi (29 km) west of Winslow in the desert of northern Arizona, United States. The site had several earlier names, and fragments of the meteorite are officially called the Canyon Diablo Meteorite, after the adjacent Cañon Diablo. Because the United States Board on Geographic Names recognizes names of natural features derived from the nearest post office, the feature acquired the name of "Meteor Crater" from the nearby post office named Meteor.
A meteoroid is a small rocky or metallic body in outer space.
Tektites are gravel-sized bodies composed of black, green, brown, or gray natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz Eduard Suess (1867–1941), son of Eduard Suess. They generally range in size from millimetres to centimetres. Millimetre-scale tektites are known as microtektites.
Impactite is rock created or modified by one or more impacts of a meteorite. Impactites are considered metamorphic rock, because their source materials were modified by the heat and pressure of the impact. On Earth, impactites are made primarily of modified terrestrial material, sometimes with pieces of the original meteorite.
Zhamanshin is a meteorite crater in Kazakhstan. It is 14 kilometres (8.7 mi) in diameter and the age is estimated to be 900,000 ± 100,000 years (Pleistocene). The crater is exposed at the surface.
Moldavite is a forest green, olive green or blue greenish vitreous silica projectile glass formed by a meteorite impact probably in southern Germany that occurred about 15 million years ago. It is a type of tektite.
Libyan Desert glass or Great Sand Sea glass is an impactite, made mostly of lechatelierite, found in areas in the eastern Sahara, in the deserts of eastern Libya and western Egypt. Fragments of desert glass can be found over areas of tens of square kilometers.
Georgiaite is a rare form of tektite found only in the state of Georgia in the southeastern United States. These tektites are found in part of the North American strewn field coming from what is believed to be the Chesapeake Bay impact crater in the late Eocene epoch over 35 million years ago. Two strewn fields and tektite groups are currently associated with this impact: the black bediasites in Texas and the green georgiaites in Georgia.
The Australasian strewnfield is the youngest and largest of the tektite strewnfields, with recent estimates suggesting it may cover 10%–30% of the Earth's surface. Research indicates that the impact forming the tektites occurred around 790,000 years ago, probably in Southeast Asia.
Darwin Crater is a suspected meteorite impact crater in Western Tasmania about 26 km (16 mi) south of Queenstown, just within the Franklin-Gordon Wild Rivers National Park. The crater is expressed as a rimless circular flat-floored depression, 1.2 km (0.75 mi) in diameter, within mountainous and heavily forested terrain. It is east of the West Coast Range and the former North Mount Lyell Railway formation.
The Allende meteorite is the largest carbonaceous chondrite ever found on Earth. The fireball was witnessed at 01:05 on February 8, 1969, falling over the Mexican state of Chihuahua. After breaking up in the atmosphere, an extensive search for pieces was conducted and over 2 tonnes (tons) of meteorite were recovered. The availability of large quantities of samples of the scientifically-important chondrite class has enabled numerous investigations by many scientists; it is often described as "the best-studied meteorite in history." The Allende meteorite has abundant, large calcium-aluminium-rich inclusions (CAI), which are among the oldest objects formed in the Solar System.
Edward Ching-Te Chao was one of the founders of the field of impact metamorphism, the study of the effects of meteorite impacts on the Earth's crust.
The term strewn field indicates the area where meteorites from a single fall are dispersed. It is also often used for the area containing tektites produced by large meteorite impact.
Charles Carter Schnetzler was a planetary scientist at NASA's Goddard Space Flight Center. Schnetzler is best known for analyzing moon rocks brought back by the Apollo program and for studying the Earth's environment using the Landsat and the Earth Observing System. Schnetzler was born in Whiting, Indiana and grew up in Neodesha, Kansas. On November 4, 2009, Schnetzler was seriously injured after being hit by a car while walking near his home on Little Patuxent Parkway in Columbia, Maryland. He later died in his home on December 15, 2009.
An Indochinite is a type of tektite. Tektites were ejected into the Earth's upper atmosphere by a meteorite impact and subsequently cooled to form the distinctive glass-like structure. Indochinites are distinctly dark black in contrast to the green of European moldavite tektites. It is estimated that these bodies of solidified magma are 700,000 years old. Indochinite tektites, as the name suggests, are found in the Indochinese peninsula, from Australia and the Pacific islands of Micronesia in the east and south, to China and Indonesia in the north and west. The largest indochinite is a Muong-Nong type tektite, which had a mass of 29.0 kg.
George Baker (1908–1975) was an Australian mineralogist, geologist, university teacher and researcher based in Melbourne, Victoria in the mid-20th century. His teaching and research work was undertaken through positions at the University of Melbourne, CSIRO and the National Museum of Victoria.
Charles Albert Edward Fenner was an Australian geologist, naturalist, geographer and educator.
