Contrary to the flow lines, these are formed by material which has been stripped off the surface and is subsequently caught again by the spinning meteorite. Sometimes a meteorite’s surface shows tear-shaped splash droplets which also point in this direction. These are named flow lines and usually point to the side of the meteorite representing the surface pointing away from the direction of flight at the moment the crust cooled. In some cases, fusion crusts develop fine lines of solidified melt. Thus, fusion crust is a snapshot of a particular moment of a meteroid’s morphological formation frozen in time. When the last melt cools, a thin, often glassy and dull coating solidifies: the fusion crust. Now the moment has come where fusion crust is formed. Once Earth’s atmosphere has slowed down our meteoroid to a point where no melting occurs, it enters the dark and cold stage of its flight. The deeper the space rock penetrates into the increasingly dense atmosphere, the more the wave of air in its path is compressed and increases in temperature. At this stage, the meteoroid has already compressed a wave of air in front of it. One can imagine the enormous front wave of compressed air that is produced by these cosmic missiles.Īt an altitude of about 70 km, where the air is less than 1 percent as dense as it is at sea level, the atmosphere begins to slow the meteoroid down. This is fast enough to cross the North American continent from east to west in 4 to 5 minutes. On iron meteorites it is almost completely composed of magnetite and even finer, regularly less than ¼ mm.įusion crust forms when meteoroids enter the gas atmosphere of our planet at speeds between 15 and 70 kilometers per second. On stone meteorites it is mainly composed of olivine, glass, wuestite and other iron oxides of the magnetite series and rarely exceeds a thickness of 1 mm. Please refer to their site for additional information.Īlways keep in mind that rocks and minerals must be examined in person for proper identification.Fusion crust, or fusion rind, is a thin melted surface layer of thermally transformed components of a meteorite. These tips for identifying a meteorite were adapted from this excellent guide from the University of New Mexico Meteorite Museum. A dense rock that leaves a black or red streak probably contains the iron minerals magnetite or hematite, respectively, neither of which are typically found in meteorites. Streak: if you scratch a meteorite on an unglazed ceramic surface, it should not leave a streak.Bubbles: volcanic rocks or metallic slag on Earth often have bubbles or vesicles in them, but meteorites do not. Light-colored crystals: Quartz is a common, light-colored crystal in Earth’s crust, but it is not found on other bodies in the solar system.Fusion crust: stony meteorites typically have a thin crust on their surface where it melted as it passed through the atmosphere.Instead, they have an irregular shape with unusual pits like finger prints in their surface called “regmaglypts.” Unusual shape: iron-nickel meteorites are rarely rounded.For “stony” meteorites, a magnet might not stick, but if you hang the magnet by a string, it will be attracted. Magnetic: Since most meteorites contain metallic iron, a magnet will often stick to them.Density: Meteorites are usually quite heavy for their size, since they contain metallic iron and dense minerals. Meteorites have several properties that help distinguish them from other rocks: They are very rare, but many people find unusual rocks or pieces of metal and wonder if they might have found a meteorite. Meteorites are fragments of rock or metal that fall to Earth from space.
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