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L Chondrite
The L type ordinary chondrites are the second most common group of meteorites, accounting for approximately 35% of all those catalogued, and 40% of the ordinary chondrites. The ordinary chondrites are thought to have originated from three parent asteroids, with the fragments making up the H chondrite, L chondrite and LL chondrite groups respectively. Name Their name comes from their relatively low iron abundance (less than 10%) with respect to the H chondrites, which are about 20–25% iron by weight. Historically, the L chondrites have been named ''hypersthene chondrites'' or ''olivine hypersthene chondrites'' for the dominant minerals, but these terms are now obsolete. Chemical composition Characteristic is the fayalite content (Fa) in olivine of 21 to 25 mol%. About 4–10% iron–nickel is found as a free metal, making these meteorites magnetic, but not as strongly as the H chondrites. Mineralogy The most abundant minerals are olivine and hypersthene (an orthopyrox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrite
A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids. Some such bodies that are captured in the planet's gravity well become the most common type of meteorite by arriving on a trajectory toward the planet's surface. Estimates for their contribution to the total meteorite population vary between 85.7% and 86.2%. Their study provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the Abiogenesis, origin of life and the presence of water on Earth. One of their characteristics is the presence of chondrules (from the Ancient Greek χόνδρος ''chondros'', grain), which are round grains formed in space as molten or partially molten droplets of distinct minerals. Chondrules typically constitute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H Chondrite
The H type ordinary chondrites are the most common type of meteorite, accounting for approximately 40% of all those catalogued, 46% of the ordinary chondrites, and 44% of all chondrites. The ordinary chondrites are thought to have originated from three parent asteroids, whose fragments make up the H chondrite, L chondrite and LL chondrite groups respectively. Name The name comes from their High iron abundance, with respect to other ordinary chondrites. Historically, the H chondrites have been named ''bronzite chondrites'' or ''olivine bronzite chondrites'' for the dominant minerals, but these terms are now obsolete. Parent body A probable parent body for this group is the S-type asteroid 6 Hebe, with less likely candidates being 3 Juno and 7 Iris. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Massalia Family
The Massalia family (adj. ''Massalian''; FIN: 404) is a family of asteroids in the inner asteroid belt, named after its parent body, 20 Massalia. It consists of S-type asteroids with very low inclinations, straddling the 1:2 resonances with Mars. There are more than 6,000 known Massalian asteroids. Characteristics This is a definite cratering family consisting of 20 Massalia and a mass of small fragments excavated from Massalia's surface by an impact. Massalia is by far the largest member with a diameter of about 150 km, while the next largest body, is only about 7 km in diameter. The mass of all the small members is negligible, less than about 1%, compared to Massalia. The family is fairly young, estimated to have been created by an impact 100 to 200 million years ago. It has a distinctly two-lobed appearance in proper ''a''--''e'' space, with one lobe centered at semi-major axes of 2.38 AU, the other at about 2.43 AU, with the parent body Massalia itself lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrite
A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids. Some such bodies that are captured in the planet's gravity well become the most common type of meteorite by arriving on a trajectory toward the planet's surface. Estimates for their contribution to the total meteorite population vary between 85.7% and 86.2%. Their study provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the Abiogenesis, origin of life and the presence of water on Earth. One of their characteristics is the presence of chondrules (from the Ancient Greek χόνδρος ''chondros'', grain), which are round grains formed in space as molten or partially molten droplets of distinct minerals. Chondrules typically constitute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
S-type Asteroid
S-type (stony-type or silicaceous-type) asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second-most common after the carbonaceous C-type. Characteristics S-type asteroids, with an astronomical albedo of typically 0.20, are moderately bright and consist mainly of iron- and magnesium-silicates. They are dominant in the inner part of the asteroid belt within 2.2 AU, common in the central belt within about 3 AU, but become rare farther out. The largest are 3 Juno (about 240–250 km across) and 15 Eunomia (230 km), with other large S-types being 29 Amphitrite, 532 Herculina and 7 Iris. These largest S-types are visible in 10x50 binoculars at most oppositions; the brightest, 7 Iris, can occasionally become brighter than +7.0, which is a higher magnitude than any asteroid except ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid Belt
The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets. The identified objects are of many sizes, but much smaller than planets, and, on average, are about one million kilometers (or six hundred thousand miles) apart. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System. The asteroid belt is the smallest and innermost circumstellar disc in the Solar System. Classes of Small Solar System body, small Solar System bodies in other regions are the near-Earth objects, the Centaur (minor planet), centaurs, the Kuiper belt objects, the scattered disc objects, the sednoids, and the Oort cloud objects. About 60% of the main belt mass is contained in the four largest asteroids: Ceres (dwarf planet), C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteoritics & Planetary Science
''Meteoritics & Planetary Science'' is a monthly peer-reviewed scientific journal published by Wiley-Blackwell on behalf of the Meteoritical Society. It specialises in the fields of meteoritics and planetary science. The journal was established as ''Meteoritics'' in 1953, adopting its current name when the scope was broadened in 1996. Since January 1, 2003, the editor-in-chief is A.J. Timothy Jull ( Arizona Accelerator Mass Spectrometry Laboratory). History The journal was established in 1953 as the successor of the ''Notes and Contributions'' that were published on behalf of the Meteoritical Society in '' Popular Astronomy'', from 1933 to 1951. Initially titled ''Meteoritics'', with the 1996 January issue the journal became ''Meteoritics and Planetary Science''. Scope Coverage encompasses planets, natural satellites, interplanetary dust, interstellar medium, lunar samples, meteors, meteorites, asteroids, comets, craters, and tektites and comes from multiple disciplines, su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martian Meteorite
A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a percent of the 72,000 meteorites that have been classified. The largest complete, uncut Martian meteorite, Taoudenni 002, was recovered in Mali in early 2021. It weighs 14.5 kilograms (32 pounds) and is on display at the Maine Mineral and Gem Museum. There are three groups of Martian meteorite: shergottites, nakhlites and chassignites, collectively known as SNC meteorites. Several other Martian meteorites are ungrouped. These meteorites are interpreted as Martian because they have elemental and isotopic compositions that are similar to rocks and atmospheric gases on Mars, which have been measured by orbiting spacecraft, surface landers and rovers. The term does not include meteorites found on Mars, such as Heat Shield Rock. Histo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium–lead Dating
Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range. The method is usually applied to zircon. This mineral incorporates uranium and thorium atoms into its crystal structure, but strongly rejects lead when forming. As a result, newly-formed zircon crystals will contain no lead, meaning that any lead found in the mineral is radiogenic. Since the exact rate at which uranium decays into lead is known, the current ratio of lead to uranium in a sample of the mineral can be used to reliably determine its age. The method relies on two separate decay chains, the uranium series from 238U to 206Pb, with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb, with a half-life of 710 million years. Decay routes Uranium decays to l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiometric Dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring Radionuclide, radioactive isotope within the material to the abundance of its Radioactive decay, decay products, which form at a known constant rate of decay. Radiometric dating of minerals and rocks was pioneered by Ernest Rutherford (1906) and Bertram Boltwood (1907). Radiometric dating is now the principal source of information about the Absolute dating, absolute age of rocks and other Geology, geological features, including the age of Paleontology, fossilized life forms or the age of Earth itself, and can also be used to date a wide range of natural and Artifact (archaeology), man-made materials. Together with stratigraphy, stratigraphic principles, ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician Meteor Event
The Ordovician meteor event was a dramatic increase in the rate at which L chondrite meteorites fell to Earth during the Middle Ordovician period, about 467.5±0.28 million years ago, lasting for about 40 million years. This rate increase is indicated by abundant fossil L chondrite meteorites in a quarry in Sweden and enhanced concentrations of ordinary chondritic chromite grains in sedimentary rocks from this time. According to a 2019 study, this temporary increase in the impact rate could have been caused by the destruction of the L chondrite parent body that was in diameter and orbited in the asteroid belt between Mars and Jupiter. This occurred around 468 ± 0.3 million years ago having scattered fragments into Earth-crossing orbits, a chronology which is also supported by shock ages in numerous L chondrite meteorites that fall to Earth today. It has been speculated that this influx contributed to, or possibly even instigated, the Great Ordovician Biodiversification Even ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromite
Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of Iron, FeChromium, Cr2Oxygen, O4. It is an oxide mineral belonging to the spinel group. The element magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (Magnesium, MgChromium, Cr2Oxygen, O4). Substitution of the element aluminium can also occur, leading to hercynite (Iron, FeAluminum, Al2Oxygen, O4). Chromite today is mined particularly to make stainless steel through the production of ferrochrome (Iron, FeChromium, Cr), which is an iron-chromium alloy. Chromite grains are commonly found in large mafic igneous intrusions such as the Bushveld in South Africa and India. Chromite is iron-black in color with a metallic Lustre (mineralogy), luster, a dark brown Streak (mineralogy), streak and a hardness on the Mohs scale of mineral hardness, Mohs scale of 5.5. Properties Chromite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
