![]() That means, with a chemical analysis, I am not likely to say, “I still don’t know” or “maybe.” A chemical analysis is a good one because it is cheaper to do than most other tests and the results are usually unambiguous. There are several different ways to determine whether or not a rock is a meteorite. They are thought to have brought volatile material to Earth when it was newly formed, helping to establish the atmosphere and other conditions required to sustain life.I suggest to persons who think that they have found a meteorite to get a chemical analysis from a lab that can provide what we geochemist call “whole-rock” elemental composition data. The most basic types, known as carbonaceous chondrites, are rich in water, sulphur and organic material. Chondrites can tell us a lot about how the solar system formed. They have been little changed compared with rocks from larger planets, which have been subjected to geological activity. There are many varieties of chondrite, with differences in mineralogy relating to the type of asteroid the meteorite came from.Ĭhondrites are the material from which the solar system formed. Their millimetre-sized granules give chondrites their name, from the Greek 'chondres' meaning sand grains. There are two main types of stony meteorite: chondrites (some of the oldest materials in the solar system) and achondrites (including meteorites from asteroids, Mars and the Moon).īoth chondrites and achondrites have many subgroups based on their compositions, structures and the minerals they contain.Īt over 4.5 billion years old, chondrites are some of the most primitive and pristine rocks in the solar system and have never been melted.Ĭhondrites have a distinctive appearance, made from droplets of silicate minerals mixed with small grains of sulphides and iron-nickel metal. The majority of meteorite finds are stony meteorites, consisting mostly of silicate minerals. Mesosiderites can therefore both record the history of both meteorites and reveal a snapshot of the conditions required for asteroids to melt and form iron cores. In the crash, molten metal mixes together with solid fragments of silicate rocks. Mesosiderites form when debris from a collision between two asteroids is mixed together. The fragments are roughly centimetre-sized and contain a mix of igneous (solidified) silicate and metal clasts (rocks made of pieces of older rocks). Mesosiderite meteorites are breccias, a variety of rock composed of broken fragments of minerals or rock cemented together by a finer material. These types of formations may also be formed by impact melting. However, other scientists think that there are very few olivine-rich meteorites in the asteroid belt, and too many pallasite meteorites for them all to have come from a core-mantle boundary. If this is the case, they could tell us a lot about the formation of Earth and other terrestrial planets. Pallasites are thought to be samples of the boundaries between a metal core and the silicate, olivine-rich mantle around it. Some scientists believe they formed in melted asteroids in a similar way to iron meteorites, where dense iron metal sinks toward the centre to form an iron core. The scientific jury is still out on exactly how pallasite meteorites formed. Elsewhere it can create a pattern of veins through solid metal. Sometimes the olivine does not occur as a single crystal but as a cluster. Pallasites contain big, beautiful olive-green crystals - a form of magnesium-iron silicate called olivine - embedded entirely in metal. ![]()
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