|
Achondrite
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. As a result, achondrites have distinct textures and mineralogies indicative of igneous processes. Achondrites account for about 8% of meteorites overall, and the majority (about two-thirds) of them are HED meteorites, possibly originating from the crust of asteroid 4 Vesta. Other types include Martian, Lunar, and several types thought to originate from as-yet unidentified asteroids. These groups have been determined on the basis of e.g. the Fe/ Mn chemical ratio and the 17O/18O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body. Classification Achondrites are classified into the following groups:O. Richard Norton. The Cambridge encyclopedia of meteorites. U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroidal Achondrite
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. As a result, achondrites have distinct textures and mineralogies indicative of igneous processes. Achondrites account for about 8% of meteorites overall, and the majority (about two-thirds) of them are HED meteorites, possibly originating from the crust of asteroid 4 Vesta. Other types include Martian, Lunar, and several types thought to originate from as-yet unidentified asteroids. These groups have been determined on the basis of e.g. the Fe/ Mn chemical ratio and the 17O/18O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body. Classification Achondrites are classified into the following groups:O. Richard Norton. The Cambridge encyclopedia of meteorites. UK ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acapulcoite
Acapulcoites are a group of the primitive achondrite class of stony meteorites. Naming and history The acapulcoites are named after the only specimen of the group, with a witnessed fall. The Acapulca meteorite fell on 11 August 1976 at 11:00 near El Quemado Colony (), outside Acapulco, Guerrero, Mexico. It had a mass of . The stone was retrieved 15 minutes afterwards from a deep crater and was cool to the touch. Following that discovery, 52 meteorite specimens have been classified as acapulcoites. Chemical composition Acapulcoites are primarily composed of olivine, orthopyroxene, plagioclase, meteoric iron, and troilite. Like all primitive achondrites, acapulcoites have chemical composition and mineralogical similarities with chondrites, some specimen even show relic chondrules. Their mineral composition lies between H and E chondrites. See also * Glossary of meteoritics This is a glossary of terms used in meteoritics, the science of meteorites. # * 2 Pallas – an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lodranite
Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with chondrites and achondrites. Naming and history The lodranite group is named after Lodhran, Pakistan, where the type specimen fell on 1 October 1868 at 14:00. Eyewitnesses of the fall reported a loud bang accompanied by a rising dust cloud to the east of the city, which led to the discovery and retrieval of the meteorite. The "meteorite from Lodran" was first described by Gustav Tschermak in 1870. He described the meteorite being "''apart from the nickel-iron it is an olivine-bronzite aggregates of such outstanding sort, that has never been found in a meteorite before only similar to the terrestrial olivine rock''". George Thurland Prior was the first to classify the lodran meteorite as the only member of the lodranite group. He als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Winonaite
Winonaites are a group of primitive achondrite meteorites. Like all primitive achondrites, winonaites share similarities with chondrites and achondrites. They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites. Naming and history The winonaite group is named after the type specimen, the Winona meteorite. The name itself derived from Winona, Arizona where the type specimen was said to be found during an archaeological excavation of the Sinagua village Elden Pueblo in September 1928. The Sinagua lived in the village between 1150 and 1275. The meteorite was said to be retrieved from the cist of one of the rooms. However, a later study indicates the meteorite was found at another Sinagua site and not in Elden Pueblo.A. L. Christenson "J. W. Simmons' account of the discovery of the Winona meteorite."''Meteorite'' 10(3):14–16, 2004. As of 2021, 54 meteorites are included in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primitive Achondrite
Primitive achondrites are a subdivision of meteorites. They are classified on the same rank (historically called "Class") and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much of their original chondritic properties. Very characteristic are relic chondrules and chemical compositions close to the composition of chondrites. These observations are explained as melt residues, partial melting, or extensive recrystallization. History The concept of primitive achondrites was first summarized in 1983. In 2006 a classification was published that assigned 7 groups to the primitive achondrites, but the classification remains controversial. The authors define primitive achondrites as meteorites "''that exceeded their solidus temperature on the parent body''" and thus would partially melt. Meteorites that have been fully melted are included if they did not reach isotopic equilibrium on their parent body. Description There ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachinite
Brachinites are a group of meteorites that are classified either as primitive achondrites or as asteroidal achondrites. Like all primitive achondrites, they have similarities with chondrites and achondrites. Brachinites contain 74 to 98% (volume) olivine. Naming and history Brachinites are named after the Brachina meteorite, the type specimen of this group, which in turn is named after Brachina, South Australia. Description Brachinites consist almost entirely of olivine (74 to 98% by volume). Other minerals include plagioclase (6.7 to 12.9%), iron sulfides (1.8 to 4.0%), clinopyroxene (1.5 to 8.2%) and orthopyroxene (0 to 2.4%). Trace minerals include phosphates and meteoritic iron. The only deviation from chondrites is the very high olivine/orthopyroxene ratio. Specimens As of 2022, there were 56 meteorites classified as brachinites. A notable example is the type specimen, the Brachina meteorite. See also * Glossary of meteoritics This is a glossary of terms used in meteoriti ... [...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 & 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. History By t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aubrite
Aubrites are a group of meteorites named for Aubres, a small achondrite meteorite that fell near Nyons, France, in 1836. They are primarily composed of the orthopyroxene enstatite and are often called enstatite achondrites. Their igneous origin separates them from primitive enstatite achondrites and means they originated in an asteroid. Aubrites are typically light-colored with a brownish fusion crust. Most aubrites are heavily brecciated; they are often said to look "lunar" in origin. Aubrites are primarily composed of large white crystals of the Fe-poor, Mg-rich orthopyroxene, or enstatite, with minor phases of olivine, nickel-iron metal, and troilite, indicating a magmatic formation under extremely reducing conditions. The severe brecciation of most aubrites attests to a violent history for their parent body. Since some aubrites contain chondritic xenoliths, it is likely that the aubrite parent body collided with an asteroid of “F-chondritic” composition. Comparisons of au ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eucrite
Eucrites are achondritic stony meteorites, many of which originate from the surface of the asteroid 4 Vesta and are part of the HED meteorite clan. They are the most common achondrite group with over 100 meteorites found. Eucrites consist of basaltic rock from the crust of 4 Vesta or a similar parent body. They are mostly composed of calcium-poor pyroxene, pigeonite, and calcium-rich plagioclase ( anorthite). Based on differences of chemical composition and features of the component crystals, they are subdivided into several groups: * Non-cumulate eucrites are the most common variety and can be subdivided further: ** Main series eucrites formed near the surface and are mostly regolith breccias lithified under the pressure of overlying newer deposits. ** Stannern trend eucrites are a rare variety. ** Nuevo Laredo trend eucrites are thought to come from deeper layers of 4 Vesta's crust, and are a transition group towards the cumulate eucrites. * Cumulate eucrites are rare typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eucrite
Eucrites are achondritic stony meteorites, many of which originate from the surface of the asteroid 4 Vesta and are part of the HED meteorite clan. They are the most common achondrite group with over 100 meteorites found. Eucrites consist of basaltic rock from the crust of 4 Vesta or a similar parent body. They are mostly composed of calcium-poor pyroxene, pigeonite, and calcium-rich plagioclase ( anorthite). Based on differences of chemical composition and features of the component crystals, they are subdivided into several groups: * Non-cumulate eucrites are the most common variety and can be subdivided further: ** Main series eucrites formed near the surface and are mostly regolith breccias lithified under the pressure of overlying newer deposits. ** Stannern trend eucrites are a rare variety. ** Nuevo Laredo trend eucrites are thought to come from deeper layers of 4 Vesta's crust, and are a transition group towards the cumulate eucrites. * Cumulate eucrites are rare typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Howardite
Howardites are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta, and as such are part of the HED meteorite clan. There are about 200 distinct members known. Characteristics They are a regolith breccia consisting mostly of eucrite and diogenite fragments, although carbonaceous chondrules and impact melt can also occur. The rock formed from impact ejecta which was later buried by newer impacts and lithified due to the pressure from overlying layers. Regolith breccias are not found on Earth due to a lack of regolith on bodies which have an atmosphere. Name Howardites are named for Edward Howard, a pioneer of meteoritics. An arbitrary divide between howardites and the polymict eucrites is a 9:1 ratio of eucrite to diogenite fragments. See also * Glossary of meteoritics This is a glossary of terms used in meteoritics, the science of meteorites. # * 2 Pallas – an asteroid from the asteroid belt and one of the likely parent bodies of the C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ureilite
Ureilite is a rare type of stony meteorite that has a unique mineralogical composition very different from that of other stony meteorites. This dark grey or brownish meteorite type is named after the village Novy Urey ( Cyrillic: ''Новый Урей''), Mordovia Republic of Russia, where a meteorite of this type fell on 4 September 1886. Notable ureilites are the Novo Urei and the Goalpara, also named for the town in which it landed (Goalpara, Assam India). On 7 October 2008, tiny asteroid 2008 TC3 entered Earth's atmosphere and exploded an estimated above the Nubian Desert in Sudan. Fragments of this asteroid were recovered the following December and were found to be ureilite. Scientists have discovered amino acids in meteorite 2008 TC3 where none were expected, taking into account high temperatures reached in the explosion of about 1000 °C. Composition A technical name for ureilite would be olivine-pigeonite achondrite. Compared to most other meteorites, ureili ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
