![]() 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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