| Acapulcoite | |
|---|---|
| — Group — | |
 NWA 2989, an example of an acapulcoite meteorite | |
| Type | Achondrite |
| Structural classification | ? |
| Class | Primitive achondrite |
| Subgroups |
|
| Parent body | Unknown |
| Composition | Olivine, orthopyroxene, plagioclase, meteoric iron, troilite |
| Total known specimens | Fifty two |
| Alternative names | Acapulcoites, Acapulcoite group, Acapulcoite meteorites |
Acapulcoites are a group of the primitive achondrite class of stony meteorites.
The acapulcoites are named after the only specimen of the group, with a witnessed fall. The Acapulco meteorite fell on 11 August 1976 at 11:00 near El Quemado Colony ( 16°52′59″N99°54′00″W / 16.883°N 99.9°W ), outside Acapulco, Guerrero, Mexico. The stone was retrieved 15 minutes afterwards from a 30 centimetres (12 in) deep crater and was cool to the touch. [1] It had a mass of 1,914 grams (67.5 oz). Following that discovery, 52 meteorite specimens have been classified as acapulcoites. [2]
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, [3] and some specimens even show relict chondrules. Their mineral composition lies between H and E chondrites. [3]
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples "bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater.
In meteoritics, a meteorite classification system attempts to group similar meteorites and allows scientists to communicate with a standardized terminology when discussing them. Meteorites are classified according to a variety of characteristics, especially mineralogical, petrological, chemical, and isotopic properties.
A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or 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%.
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.
Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small proportion (4.6%) of meteorite falls.
The Murchison meteorite is a meteorite that fell in Australia in 1969 near Murchison, Victoria. It belongs to the carbonaceous chondrite class, a group of meteorites rich in organic compounds. Due to its mass and the fact that it was an observed fall, the Murchison meteorite is one of the most studied of all meteorites.
The Tagish Lake meteorite fell at 16:43 UTC on 18 January 2000 in the Tagish Lake area in northwestern British Columbia, Canada.
The LL chondrites are a group of stony meteorites, the least abundant group of the ordinary chondrites, accounting for about 10–11% of observed ordinary-chondrite falls and 8–9% of all meteorite falls. 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. The composition of the Chelyabinsk meteorite is that of a LL chondrite meteorite. The material makeup of Itokawa, the asteroid visited by the Hayabusa spacecraft which landed on it and brought particles back to Earth also proved to be type LL chondrite.
The Allende meteorite is the largest carbonaceous chondrite ever found on Earth. The fireball was witnessed at 01:05 on February 8, 1969, falling over the Mexican state of Chihuahua. After it broke up in the atmosphere, an extensive search for pieces was conducted and over 2 tonnes were recovered. The availability of large quantities of samples of the scientifically important chondrite class has enabled numerous investigations by many scientists; it is often described as "the best-studied meteorite in history." The Allende meteorite has abundant, large calcium–aluminium-rich inclusions (CAI), which are among the oldest objects formed in the Solar System.
CI chondrites, also called C1 chondrites or Ivuna-type carbonaceous chondrites, are a group of rare carbonaceous chondrite, a type of stony meteorite. They are named after the Ivuna meteorite, the type specimen. CI chondrites have been recovered in France, Canada, India, and Tanzania. Their overall chemical composition closely resembles the elemental composition of the Sun, more so than any other type of meteorite.
Primitive achondrites are a subdivision of meteorites. They are classified on the same rank 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.
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.
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.
IAB meteorites are a group of iron meteorites according to their overall composition and a group of primitive achondrites because of silicate inclusions that show a strong affinity to winonaites and chondrites.
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.
The Zakłodzie meteorite is a stony-iron meteorite found in Poland in 1998. Its mass is 8.68 kilograms (19.1 lb). It is composed predominantly from enstatite and meteoric iron. Currently classified as an ungrouped enstatite achondrite its classification is still an ongoing scientific debate.
The Itqiy meteorite is an enstatite-rich stony-iron meteorite. It is classified as an enstatite chondrite of the EH group that was nearly melted and is therefore very unusual for that group. Other classifications have been proposed and are an ongoing scientific debate.
This is a glossary of terms used in meteoritics, the science of meteorites.
Österplana 065 is an Ordovician fossil meteorite found in the Thorsberg quarry in Sweden on June 26, 2011, and scientifically described in 2016. Measuring 8×6.5×2 cm, it impacted the Earth 470 million years ago, during the Ordovician According to the naming conventions of the Meteoritical Society, the meteorite was named after the locality at which it was found, Österplana.
CM chondrites are a group of chondritic meteorites which resemble their type specimen, the Mighei meteorite. The CM is the most commonly recovered group of the 'carbonaceous chondrite' class of meteorites, though all are rarer in collections than ordinary chondrites.