Carbonaceous chondrites or C chondrites are a class of

chondritic 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 prim ...

meteorite 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 Natural satellite, moon. When the ...

s 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 fall A meteorite fall, also called an observed fall, is a meteorite collected after its fall from outer space was observed by people or automated devices. Any other meteorite is called a "find". There are more than 1,100 documented falls listed in w ...

s. Some famous carbonaceous chondrites are: Allende, Murchison, Orgueil, Ivuna,

Murray Murray may refer to: Businesses * Murray (bicycle company), an American manufacturer of low-cost bicycles * Murrays, an Australian bus company * Murray International Trust, a Scottish investment trust * D. & W. Murray Limited, an Australian who ...

, Tagish Lake, Sutter's Mill and

Winchcombe Winchcombe () is a market town and civil parish in the Borough of Tewkesbury in the county of Gloucestershire, England, it is 6 miles north-east of Cheltenham. The population was recorded as 4,538 in the 2011 census and estimated at 5,347 in ...

General description

C chondrites contain a high proportion of carbon (up to 3%), which is in the form of

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

s and organic compounds, including

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s. In addition, they contain water and minerals that have been modified by the influence of water. The carbonaceous chondrites were not exposed to higher temperatures, so that they are hardly changed by thermal processes. Some carbonaceous chondrites, such as the

Allende meteorite 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 ...

, contain calcium-aluminum-rich inclusions (CAIs). These are compounds that emerged early from the primeval

solar nebula The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a ...

, condensed out and represent the oldest minerals formed in the

solar system The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. Some primitive carbonaceous chondrites, such as the CM chondrite Murchison, contain presolar minerals, including moissanite (natural silicon carbide) and tiny nanometer-sized diamonds that apparently were not formed in our solar system. These presolar minerals were probably formed during the explosion of a nearby

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

or in the vicinity of a pulsating

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

(more precisely: a so-called

AGB star The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late ...

) before they got into the cloud of matter from which our solar system was formed. Such star explosions release pressure waves that can condense clouds of matter in their surroundings, leading to the formation of new ones, stars and solar systems. Another carbonaceous chondrite, the Flensburg meteorite (2019), provides evidence of the earliest known occurrence of liquid water in the young solar system to date.

Composition and classification

Carbonaceous chondrites are grouped according to distinctive compositions thought to reflect the type of parent body from which they originated. These C chondrite groups are now each named with a standard two-letter CX designation, where C stands for "carbonaceous" (other types of

chondrites A chondrite is a stony (non-Metallicity, 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 ea ...

do not begin with this letter) plus a capital letter in the spot ''X'', which is very often the first letter of the name of a prominent meteorite—often the first to be discovered—in the group. Such meteorites are often named for the place where they fell, thus giving no clue as to the physical nature of the group. Group CH, where H is for "high metal" is so far the only exception. See below for name derivations of each group. Several groups of carbonaceous chondrites, notably the CM and CI groups, contain high percentages (3% to 22%) of

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, as well as

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

s. They are composed mainly of

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

s and

sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...

s, with the minerals

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

and

serpentine Serpentine may refer to: Shapes * Serpentine shape, a shape resembling a serpent * Serpentine curve, a mathematical curve * Serpentine, a type of riding figure Science and nature * Serpentine subgroup, a group of minerals * Serpentinite, a ...

being characteristic. The presence of volatile organic chemicals and water indicates that they have not undergone significant heating (>200 °C) since they were formed, and their compositions are considered to be close to that of the

from which the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

condensed. Other groups of C chondrites, e.g., CO, CV, and CK chondrites, are relatively poor in volatile compounds, and some of these have experienced significant heating on their parent asteroids.

CI group

This group, named after the

Ivuna meteorite 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 (mineralogy), type specimen. CI c ...

(Tanzania), have chemical compositions that are close to that measured in the solar photosphere (aside from gaseous elements, and elements such as lithium which are underrepresented in the Sun's photosphere by comparison to their abundance in CI chondrites). In this sense, they are chemically the most primitive known meteorites. CI chondrites typically contain a high proportion of water (up to 22%), and organic matter in the form of

s and PAHs. Aqueous alteration promotes a composition of hydrous phyllosilicates,

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

, and

crystals occurring in a black matrix, and a possible lack of

chondrule A chondrule (from Ancient Greek χόνδρος ''chondros'', grain) is a round grain found in a chondrite. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids. Because chondrites repres ...

s. It is thought they have not been heated above , indicating that they condensed in the cooler outer portion of the solar nebula. Five CI chondrites have been observed to fall: Ivuna, Orgueil, Alais, Tonk, and Revelstoke. Several others have been found by Japanese field parties in Antarctica. In general, the extreme fragility of CI chondrites causes them to be highly susceptible to terrestrial weathering, and they do not survive on Earth's surface for long after they fall.

CV group

This group takes its name from Vigarano (Italy). Most of these chondrites belong to the petrologic type 3. CV chondrites observed falls: * Allende
BaliBukharaGrosnajaKabaMokoiaVigarano

CM group

The group takes its name from Mighei (Ukraine), but the most famous member is the extensively studied Murchison meteorite. Many falls of this type have been observed and CM chondrites are known to contain a rich mix of complex organic compounds such as amino-acids and purine/pyrimidine nucleobases. CM chondrite famous falls: * Murchison * Sutter's Mill
Aguas Zarcas
* Jbilet Winselwan *

Winchcombe meteorite The Winchcombe meteorite is a meteorite that was observed entering the Earth's atmosphere as a fireball over Gloucestershire, England at 21:54 hours on 28 February 2021. Due to a public appeal, fragments were quickly recovered from the village o ...

CR group

The group takes its name from Renazzo (Italy). The best

parent body In meteoritics, a parent body is the celestial body from which originates a meteorite or a class of meteorites. Identification The easiest way to correlate a meteorite with a parent body is when the parent body still exists. This is the case fo ...

candidate is

2 Pallas Pallas (minor-planet designation: 2 Pallas) is the second asteroid to have been discovered, after Ceres. It is believed to have a mineral composition similar to carbonaceous chondrite meteorites, like Ceres, though significantly less hyd ...

. CR chondrites observed falls: * Al Rais * Kaidun * Renazzo Other famous CR chondrites:
Dar al Gani 574
* El Djouf 001 * Northwest Africa 801

CH group

"H" stands for "high metal" because CH chondrites may contain up to as much as 40% of metal. That makes them one of the most metal-rich of any of the chondrite groups, second only to the CB chondrites and some ungrouped chondrites such as NWA 12273. The first meteorite discovered was ALH 85085. Chemically, these chondrites are closely related to CR and CB groups. All specimens of this group belong only to petrologic types 2 or 3."Carbonaceous chondrite" Meteorite.fr: All About Meteorites: Classification

CB group

Gujba meteorite, bencubbinite (14785860604)

The group takes its name from the most representative member
Bencubbin
(Australia). Although these chondrites contain over 50% nickel-iron metal, they are not classified as

mesosiderite Mesosiderites are a class of stony–iron meteorites consisting of about equal parts of metallic nickel-iron and silicate. They are breccias with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained ...

s because their mineralogical and chemical properties are strongly associated with CR chondrites.

CK group

This group takes its name from Karoonda (Australia). These chondrites are closely related to the CO and CV groups.

CO group

The group takes its name from

Ornans Ornans () is a commune in the Doubs department in the Bourgogne-Franche-Comté region in eastern France. On January 1, 2016, the former commune Bonnevaux-le-Prieuré was merged into Ornans.Ornans Ornans () is a commune in the Doubs department in the Bourgogne-Franche-Comté region in eastern France. On January 1, 2016, the former commune Bonnevaux-le-Prieuré was merged into Ornans.KainsazWarrenton
*

Moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

Famous finds: *

Dar al Gani 749 Dar or DAR may refer to: Settlements * Dar es Salaam, the largest city of Tanzania and East Africa * Dar, Azerbaijan, a village * Dar, Iran, a village People * Dar (tribe), a Kashmiri tribe in India and Pakistan * Aleem Dar, Pakistani crickete ...

CL group

Officially recognized in 2022 after minimum specimens (five) described. CL chondrites, named after type specimen(s) Loongana, are chondrite-rich, metal-rich, and volatile-poor.

C ungrouped

The most famous members: * Tagish Lake *Tarda

Organic matter

Ehrenfreund et al. (2001) found that amino acids in Ivuna and Orgueil were present at much lower concentrations than in CM chondrites (~30%), and that they had a distinct composition high in β- alanine, glycine, γ- ABA, and β-ABA but low in α-aminoisobutyric acid (AIB) and

isovaline Isovaline is a rare amino acid transported to earth by the Murchison meteorite, which landed in Australia in 1969. The discovery of isovaline in the biosphere demonstrates an extraterrestrial origin of amino acids and has been linked to the homoc ...

. This implies that they had formed by a different synthetic pathway, and on a different parent body from the CM chondrites. Most of the

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

in CI and CM carbonaceous chondrites is an insoluble complex material. That is similar to the description for kerogen. A kerogen-like material is also in the ALH84001 Martian meteorite (an achondrite). The CM meteorite Murchison has over 70 extraterrestrial

s and other compounds including

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

s, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

s, fullerenes, heterocycles, carbonyl compounds,

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...