CI chondrite: Difference between revisions

CI chondrite
CI chondrite
— Group —
	Three non-CI carbonaceous chondrite samples- Allende (CV), Tagish Lake (C-ungr), Murchison (CM)
Type	Chondrite
Structural classification	?
Class	Carbonaceous chondrite
Subgroups	None?;
Parent body	Unknown
Composition	?
Total known specimens	Debated: 5–10+
TKW	17 kilograms (37 lb)
Alternative names	CI chondrites, C1 chondrites, CI chondrite meteorites, C1 chondrite meteorites

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CI chondrites, sometimes C1 chondrites, are a group of rare stony meteorites belonging to the carbonaceous chondrites. Samples have been discovered in France, Canada, India, and Tanzania. Compared to all the meteorites found so far, their overall chemical composition most closely resembles the elemental distribution in the sun's photosphere. Currently, borderline CI specimens found in Antarctica may or may not receive their own group, CY chondrites.

Designation

The abbreviation CI is derived from the C for carbonaceous and from the I for Ivuna, the type locality in Tanzania. The 1 in C1 stands for the type 1 meteorites in the classification scheme of Van Schmus-Wood. Type 1 meteorites, by definition, have no fully-visible chondrules.

History

There are very few finds of CI chondrites, five or so altogether (see section). The oldest find dates back to the year 1806: a meteorite was seen near Alès (or Alais) in France. Consequently, pieces weighing 6 kilograms were discovered at Saint-Étienne-de-l'Olm and Castelnau-Valence, small villages southeast of Alès. In 1864 another fall happened in France at Orgueil near Montauban. The meteorite had disintegrated into 20 pieces weighing a total of 10 kilograms. In 1911 a meteorite was seen near Tonk (Rajasthan) in India. Only a few fragments were recovered that weighed a mere 7.7 grams (0.27 oz).^[1] The meteorite of the type locality Ivuna in Tanzania fell in 1938 splitting into three pieces of altogether 705 grams (24.9 oz). This was followed in 1965 by a very bright fall in Revelstoke, British Columbia, but only two tiny fragments of 1 gram (0.035 oz) were found. All in all roughly 17 kilograms of CI-chondrites exist so far.

CI Chondrites
Name	Fall date	Country	TKW	Ref.
Alais	1806	France	6 kg	^[2]
Orgueil	1864	France	14 kg	^[3]
Tonk	1911	India	7.7g	^[4]
Ivuna	1938	Tanzania	705g	^[5]
Revelstoke	1965	Canada	1.6g	^[6]

Classification

CI chondrites are very fragile and porous rocks, which easily disintegrate on their descent through the atmosphere; this explains why mainly small fragments have been discovered so far. A good example is the very bright Revelstoke fall. Despite a bolide which "gave promise of being big", it yielded only two tiny fragments weighing below one gram- "the dubious distinction of being the smallest recovered meteorite" [at the time].^[7] CI chondrites are characterized by a black fusion crust which sometimes is difficult to distinguish from the very similar matrix. The opaque matrix is rich in carbonaceous material and contains black minerals like magnetite and pyrrhotite. At some places white, water-bearing carbonates and sulfates are incorporated.

Chemistry- Solar (System) Reference Standard

The defining feature of CI meteorites is their chemical composition, rich in volatile elements- richer than any other meteorites. The element assay of CI meteorite is used as a geochemical standard, as it has "a remarkably close relationship"^[8] to the makeup of the Sun and greater Solar System.^[9]^[10] This abundance standard is the measure by which other meteorites,^[11]^[12]^[13] comets,^[14]^[15]^[16]^[17] and in some cases the planets themselves^[18]^[19]^[20]^[15] (since revised^[21]^[22]) are assayed.

Goldschmidt noted the primitive (pre-differentiated) compositions of some meteorites, calling it the "cosmic" abundance- he assumed meteorites had arrived from free space, not our Solar System.^[23]^[24] In turn, the study of such abundances stimulated- then validated- work in nucleosynthesis and stellar physics.^[25]^[12] In a sense, Goldschmidt's choice of terms may have been borne out: both Solar and CI compositions appear similar to nearby stars as well,^[26]^[27] and presolar grains exist (though too small to be relevant here).

The CI abundance is more properly linked to the abundances in the solar photosphere. Small differences exist between the solar interior, photosphere, and corona/solar wind. Heavy elements may settle to the interiors of stars (for our Sun, this effect appears low^[27]); the corona and thus the solar wind are affected by plasma physics and high-energy mechanisms and are imperfect samples of the Sun.^[14]^[15] Other issues include the lack of spectral features- and thus, straightforward photospheric observation- of noble gases.^[25] Since the CI values are measured directly (first by assay, now by mass spectrometry, and when necessary, neutron activation analysis), they are more precise than solar values, which are subject to (besides the above field effects) spectrophotometric assumptions, including elements with conflicting spectral lines. In particular, when the iron abundances of CIs and the Sun did not match,^[28]^[29] it was the solar value that was questioned and corrected, not the meteorite number.^[26]^[30] Solar and CI abundances, for better and for worse, differ in that e. g., chondrites condensed ~4.5 billion years ago and represent some initial planetary states (i. e., the proto-solar abundance),^[31]^[32] while the Sun continues burning lithium^[33] and possibly other elements^[25]^[27]^[12] and continually creating helium from e. g., deuterium.

Issues with CI abundances include heterogeneity (local variation),^[34]^[35] and bromine and other halogens, which are water-soluble and thus labile.^[33]^[14]^[36]^[22] Volatiles, such as noble gases (though see below) and the atmophile elements carbon, nitrogen, oxygen, etc. are lost from minerals and not assumed to hold the Solar correspondence. However, in the modern era the Solar carbon and oxygen measurements have come down significantly.^[25]^[37]^[38] As these are the two most abundant elements after hydrogen and helium, the Sun's metallicity is affected significantly.^[38]^[39] It is possible that CI chondrites may hold too many volatiles, and the matrix of CM chondrites (excluding chondrules, calcium–aluminium-rich inclusions, etc.), or bulk Tagish Lake, may be a better proxy for the Solar abundance.^[33]^[40]^[41]

Oxygen

Oxygen is the chief element in CI- and many other- meteorites. Despite the Solar agreement, the common elements carbon and nitrogen rarely condense into minerals for inclusion and recovery as meteorites. Instead, they tend to form various gases. They were depleted in the early eras of the Solar System, while oxygen forms numerous oxides.

Oxygen isotope studies had been performed before the modern era, both on Earth rocks and meteorites.^[42]^[43] However, isotope differences in individual samples (excepting radiosotopes) had once been widely held to be local effects, caused by separation processes (plus spallation, captures, etc.)- the materials had nevertheless all formed from a common pool, with a single oxygen mixture. The fall and analysis of the Allende meteorite, with large amounts of material available for study, demonstrated clearly that the Solar System contained different oxygen reservoirs, with different isotope ratios.^[44]^[45]

The three stable O-isotopes are ¹⁶O, ¹⁷O, and ¹⁸O. A "three-isotope plot" (¹⁷O/¹⁶O axis versus ¹⁸O/¹⁶O axis) shows different Solar System materials- and thus, their oxygen reservoirs and likely, different formation regions- in different fields. The CI chondrites are clearly distinguished isotopically from their petrological kin, the CM chondrites, by their field: CIs are enriched in ¹⁸O, and to a lesser extent ¹⁷O, compared to CMs, with no overlap between them. The Antarctic (CI, CI-like, and/or CY) meteorites are even more enriched in ¹⁸O. These are the macroscopic samples with the heaviest oxygen in the Solar System. Oxygen isotope studies and classification have gone on to other meteorite groups, classes, and more astromaterials.^[46]^[47]^[48]^[49]^[45]

Iron

Iron is present with 25 weight %, but mainly compounded in phyllosilicates and oxides (magnetite)- see below. This is a marginally higher level than CM chondrites, as iron is somewhat cooler-forming than magnesium. The siderophiles nickel and cobalt follow iron as well.^[50]

The majority of the iron is in the form of cations in the phyllosilicates and iron bound as magnetite. Some appears as ferrihydrite,^[51] but not in Ivuna.^[52]

Carbon

CIs average ~3.8% carbon, with excursions from 2-5%. This is the highest of the carbonaceous chondrites, but not of all meteorites- some ureilites may contain more.

The carbon is in the form of native carbon (graphite, nanodiamonds, etc.), and carbonates,^[53]^[54] but the bulk is dispersed as globules of organics.

Organics in CIs include a lesser amount of soluble fractions, and a majority of macromolecular (insoluble) organics such as PAHs.

Gas

All carbonaceous meteorites are, to some extent, gas-rich.^[55]^[56]^[57] Orgueil,^[58]^[38] Alais, Ivuna^[59] and Tonk all assay to higher gas levels than typical meteorites-^[60] Revelstoke is too small for traditional measurements.^[61]^[13]

Most gases store mostly in carbon. Carbon's numerous allotropes form numerous network solids, able to store atoms in their lattices. Gases are often found in "dark" CM-like deposits,^[56] "an extraordinary absorber", and in magnetite^[62]^[63]

Petrology

The main petrologic characteristic of Type 1 chondrites, such as CIs, is the lack of recognizable chondrules, thus excepting the sample from Tagish Lake. Yet small chondrule fragments and calcium-aluminium-rich inclusions (CAI's) do occur, but are quite rare.^[64]

Phyllosilicates and Aqueous Alteration

Though CM chondrites also have large amounts of phyllosilicates,^[65]^[66] CI chondrites are distinguished petrologically by a near-absence of anything but phyllosilicate matrix, per their Type 1 designation.^[67]^[68] CMs are predominantly tochilinite-cronstedtite intergrowths ("TCI"), while CIs hold serpentinite-smectite (often saponite) layers.^[69]^[51]^[52]^[70] In both cases, the two minerals form sheets alternating at the molecular level; the phyllosilicate then holds hydroxide ions (OH^-) or true water (H₂O) bound between layers (possibly both, in the case of multilayers).^[71] Serpentinite and saponite were identified by their characteristic 7-Angstrom and ~12-Angstrom sheet spacings, respectively.^[72]^[52]^[73]

These phyllosilicates are the products of aqueous alteration, when the original protosolar condensates olivine and pyroxene, with ionic bonds between their components, are subject to water, often with heating.^[74]^[75]^[76] The debate is whether this alteration, in general, happened at free-floating particles (the nebular hypothesis)^[77] or within the meteorites (or their parent small bodies)- the parent body hypothesis.^[78] On CI chondrites, the existence of veins, and multiple morphologies of magnetite, suggest possibly both, in multiple episodes.^[79]^[51]^[52]^[49]^[80]

It is peculiar that extensively-altered material should yet have the most primitive element abundances.^[81] Whatever aqueous processes shaped CI chondrites either did not drive minerals farther than mm- to cm-scale, or the parent body was so thoroughly fluidized that all volumes which became the CI chondrites were homogenized-^[82]^[73]^[22]^[83] in either case, a closed system.^[45]

Aqueous alteration has proceeded toward the point of no free (metallic) metal. All or essentially all metal grains are now bound as oxides, sulfides, etc.^[84]

In the case of Antarctic finds (the putative CY chondrites), this process has partially reversed. Phyllosilicates have, to some extents, dehydrated and reverted to silicates^[85]^[72]^[82]^[86] suggesting a different parent body for those meteorites.^[87]

This water can be extracted artificially by thermogravimetric analysis: using heat to drive off volatiles from their storage. Temperatures vary with the form and host. In the case of hydroxide, two such ions hydroxylate each other, to give one water molecule and one oxygen molecule:^[88]^[89]^[90]

2 OH → H₂O + O₂

Water

CI chondrites contain between 17 and 22 weight % water. Their high porosity (of up to 30%) seems to be correlated to that fact. The water is mostly tied up in water-bearing silicates. Strong aqueous alteration at rather low temperatures (at 50 to 150 °C)^[91] – a hallmark of CI chondrites – is indicated by the occurrence of minerals like epsomite, but also by carbonates and sulfates. Liquid water must have penetrated the parent body through cracks and fissures and then deposited the water-bearing phases.

Fluid inclusions have been identified in other meteorites,^[92]^[93] and the CI chondrites Ivuna, and likely Orgueil.^[94]^[95] Such brine samples are the only direct surviving fluids that can be studied from the early solar system.

Magnetite

Elemental iron is essentially absent, converted to e. g., magnetite. Though found in many meteorites, magnetite is common and characteristic of the carbonaceous chondrites, and especially of CIs.^[96]. Magnetite abundance is ~4%, second after phyllosilicates;^[97] it takes many sizes and morphologies^[98]^[99]^[100]

These morphologies include conventional crystals, spheres and spheroids. Sphere(oids) are multiple sizes^[96]^[79] unlike CM^[63] "Framboids" (fr. raspberry) are round clusters of round spheroids.^[98]^[79]^[80] "Plaquettes" resemble stacks of dishes, threads, or beehives.^[98]^[100]^[80] They are characteristic of CIs, and not found in CMs.^[68]

Magnetite originated from continuing oxidation of sulfides: nominally troilite (stoichiometric FeS) but de facto pyrrhotite (Fe_(1-x)S) with pentlandite, pyrite, and their nickel substitutions, etc.^[101]^[102]^[103]This oxidation appears to have occurred in multiple generations.^[103]^[104]

Iron sulfides like pyrrhotite, pentlandite, troilite and cubanite do occur, but ^[105] The Mg/Si ratio of 1.07 is rather high.^[106] Only CV chondrites are more strongly enriched in magnesium. The Ca/Si ratio of 0.057 is the lowest of all carbonaceous chondrites.^[107] As regards the oxygen isotopes, CI chondrites have the highest values in δ¹⁷O and δ¹⁸O among the carbonaceous chondrites, though see Antarctic specimens, below. The ratio 17/18 compares with terrestrial values (on the "TFL," the terrestrial fractionation line).

Magnetite's oxygen is clearly lighter isotopes.^[108] It acts as a carrier phase for xenon.^[109]^[63]

Other components

The phyllosilicate matrix is hosting intact mineral grains such as olivine/pyroxene, carbonates, sulfates, sulfides, and magnetite. CI-chondrites contain the following minerals:

olivine (forsterite with fayalite Fa_{10 – 20}).
clinopyroxene.
orthopyroxene.

All these ferromagnesian silicates are tiny, equidimensional, idiomorphic grains crystallized at high temperatures.

magnetite. Occurs as framboids, spherulites and platelets.
pyrrhotite.
cubanite. Intergrown with pyrrhotite.
pentlandite.
troilite.

Water-bearing, clay-rich phyllosilicates like montmorillonite and serpentine-like minerals. Main constituents. As aqueous alteration minerals occur:

epsomite. In microscopic veins.
vaterite.
carbonates.
sulfates.

Carbonaceous minerals include:

The ferromagnesian minerals are isolated and show no signs of alteration.^[110]

Physical parameters

Because of their high porosity, CI chondrites have only a density of 2.2 g/cm³.

Natural History

Formation

CI chondrites and the closely related CM chondrites are very rich in volatile substances, especially in water. It is assumed that they originally formed in the outer asteroid belt, at a distance surpassing 4 AU – the reason for this being the so-called snow line situated at this distance and representing a temperature of 160 K. At these conditions any water present condensed to ice and was therefore preserved. This is supported by the similarity of CI chondrites with the icy moons of the outer Solar system. Furthermore, there seems to exist a connection to comets: like the comets, CI chondrites accreted silicates, ice and other volatiles, as well as organic compounds (example: Comet Halley).

Occurrence

Micrometeorites/Dust

Ceres

Comets?

Antarctic CI chondrites (?)

Antarctica has been a fertile source of meteorites. Greater yields from the continent's ice fields have resulted in arguably CI or CI-like specimens, starting with Yamato 82042 and 82162 (Y 82042, Y82162). In 1992, Ikeda proposed that these meteorites, differing somewhat from non-Antarctic examples, should receive their own grouplet-^[111] at the time, there were, three, short of the five (unpaired) meteorites needed for a full group.^[112]^[113]^[114] These meteorites have measurably higher sulfide content, and an ¹⁸O level even higher than the prior CI specimens, making them the heaviest in oxygen of all meteorites found.

By 2015, the specimen list had grown: arguably Y 86029, 86720, 86789, 980115, Belgica 7904 and a desert chondrite, Dhofar 1988. King et al. renewed the call for a separate group, the "CY" chondrites.^[115]^[116]

Misclassification

Due to their rarity, and importance as geochemical references, many are eager to claim specimens as CI.

Bench Crater Sample

During the Apollo 12 mission a meteorite was found 1969 on the moon, which was first thought to be a CI chondrite, but later turned out to be a closely related CM chondrite.

Kaidun

In 1983, Kallemeyn and Kerridge claimed that the Kaidun meteorite was a potential CI.^[117] As the CR chondrite group was still under debate by the meteoritical community, CI appeared more appropriate at the time. Kaidun is officially a CR2.

Tagish Lake Meteorite

In 2000 a fall occurred at Tagish Lake in the Yukon Territory. This meteorite is not included within the CI chondrites, as it contains chondrules. It is designated C2-ungrouped (ung).

The meteorite is "no doubt" a type 2, petrographically.^[118]^[119] Chemical abundances are "very similar" to CM, "distinctly higher than the CI chondrite" levels.^[120] Although the carbon and nitrogen isotopes are closer to CI,^[121] the oxygen isotopes, which predominate, are not CI-like. Tagish Lake is enriched in ¹⁷O, but deficient in ¹⁸O, placing it closer to the CM meteorites and on the CCAM (carbonaceous chondrite anhydrous mineral mixing) line with the CM-CO clan.^[122]^[123]^[124]

Friedrich et al. conclude "[as to] Tagish Lake being a CI chondrite: it is not."^[125]

NWA 5958

In 2011, another research group claimed the Northwest Africa 5958 meteorite (NWA 5958) was a CI.^[126]

A later team reported that it is not.^[127] NWA 5958 is a C2-ung.

Importance

Compared to all the meteorites found to date, CI chondrites possess the strongest similarity to the elemental distribution within the original solar nebula. For this reason they are also called primitive meteorites. Except for the volatile elements carbon, hydrogen, oxygen and nitrogen, as well as the noble gases, which are deficient in the CI chondrites, the elemental ratios are nearly identical. Lithium is another exception, it is enriched in the meteorites (lithium in the Sun is involved during nucleosynthesis and therefore diminished).

Because of this strong similarity, it has become customary in petrology to normalize rock samples versus CI chondrites for a specific element, i. e. the ratio rock/chondrite is used to compare a sample with the original solar matter. Ratios > 1 indicate an enrichment, ratios < 1 a depletion of the sample. The normalization process is used mainly in spider diagrams for the rare-earth elements.

CI chondrites also have a high carbon content. Besides inorganic carbon compounds like graphite, diamond and carbonates, organic carbon compounds are represented. For instance, amino acids have been detected. This is a very important fact in the ongoing search for the origin of life.

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[aka8-72] Akai J. (1988). "Incompletely transformed serpentine-type phyllosilicates in the matrix of Antarctic CM chondrites". Geochim. Cosmochim. Acta. 52: 1593–99.

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[93] Tsuchiyama, A.; Miyake A.; Okuzumi S.; Kitayama A.; Kawano J.; Uesugi K.; Takeuchi A.; Nakano T.; Zolensky M. (2021). "Discovery of primitive CO2-bearing fluid in an aqueously altered carbonaceous chondrite". Science Advances. 7 (17): eabg9707. doi:10.1126/sciadv.abg9707.

[say1-94] Saylor, J.; Zolensky M.; Bodnar R.; Le L.; Schwandt C. (2001). Fluid Inclusions In Carbonaceous Chondrites. LPS XXXII. p. 1875.

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[rahmd-96] Rahmdor, P. (1963). "The Opaque Minerals in Stony Meteorites". J. Geophys. Res. 68 (7): 2011. very common" "characteristic

[97] Alfing, J.; Patzek, M.; Bischoff, A. (2019). "Modal Abundances of coarse-grained (>5um) components within CI-chondrites and their individual clasts − Mixing of various lithologies on the CI parent body(ies)". Geochem. 79 (4): 125532.

[jedwab67-98] Jedwab, J. (1967). "La Magnetite en Plaquettes des Meteorites carbonees D'Alais, Ivuna et Orgueil". Earth Planet. Sci. Lett. 2: 440–444.

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[tom150-104] Cite error: The named reference tom150 was invoked but never defined (see the help page).

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[118] Brown, P. G.; Hildebrand, A. R.; Zolensky, M. E. (2002). "Tagish Lake". Meteoritics & Planetary Science. 37 (5): 619–21.

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@@ Line 38: / Line 38: @@
 |+ CI Chondrites
 |-
-| Name || [[Meteorite fall|Fall date]] || Country || Ref.
+| Name || [[Meteorite fall|Fall date]] || Country || [[Total known weight|TKW]] || Ref.
 |-
-|  [[Alais_meteorite|Alais]] || 1806 || France || <ref>{{cite journal |last1=Thenard |first1=L. J.|title=Analyse d'un aerolithe tombe dans l'arrondisement d'Alais | date=1806 |journal=Ann. Chim. et Phys. |volume=59 |page=103 }}</ref>
+|  [[Alais_meteorite|Alais]] || 1806 || France || 6 kg || <ref>{{cite journal |last1=Thenard |first1=L. J.|title=Analyse d'un aerolithe tombe dans l'arrondisement d'Alais | date=1806 |journal=Ann. Chim. et Phys. |volume=59 |page=103 }}</ref>
 |-
-| [[Orgueil meteorite|Orgueil]] || 1864 || France || <ref>{{cite journal |last1=Pisani  |first1=F. |title=Etude Chimique et analyse d'aerolithe d'Orgueil | date=1864 |journal=Comptes Rendus de l'Academie des Sciences Paris |volume=59 |issue= |pages=132-35 }}</ref>
+| [[Orgueil meteorite|Orgueil]] || 1864 || France || 14 kg || <ref>{{cite journal |last1=Pisani  |first1=F.14 kg |title=Etude Chimique et analyse d'aerolithe d'Orgueil | date=1864 |journal=Comptes Rendus de l'Academie des Sciences Paris |volume=59 |issue= |pages=132-35 }}</ref>
 |-
-| [[Tonk meteorite|Tonk]] || 1911 || India || <ref>{{cite journal |last1=Christie |first1=W. A. K. |date=1914 |title=A Carbonaceous Aerolite from Rajputana |journal=Rec. Geol. Surv. India |volume=44 |pages=41-51 }}</ref>
+| [[Tonk meteorite|Tonk]] || 1911 || India || 7.7g || <ref>{{cite journal |last1=Christie |first1=W. A. K. |date=1914 |title=A Carbonaceous Aerolite from Rajputana |journal=Rec. Geol. Surv. India |volume=44 |pages=41-51 }}</ref>
 |-
-| [[Ivuna meteorite|Ivuna]] || 1938 || Tanzania || <ref>{{cite journal |last1=McSween |first1=H. Y. |last2= Richardson |first2=S. M. |date=1977 |title=The composition of carbonaceous chondrite matrix |journal=Geochim. Cosmochim. Acta |volume=41 |pages=1145-61 }}</ref>
+| [[Ivuna meteorite|Ivuna]] || 1938 || Tanzania || 705g || <ref>{{cite journal |last1=McSween |first1=H. Y. |last2= Richardson |first2=S. M. |date=1977 |title=The composition of carbonaceous chondrite matrix |journal=Geochim. Cosmochim. Acta |volume=41 |pages=1145-61 }}</ref>
 |-
-| [[Revelstoke meteorite|Revelstoke]] || 1965 || Canada || <ref>{{cite journal |last1=Folinsbee |first1=R. E. |last2=Douglas |first2=J. A. V. |date=1967 |title=Revelstoke, a new Type I carbonaceous chondrite |journal=Geochim. Cosmochim. Acta |volume=31 |pages=1625-35 }}</ref>
+| [[Revelstoke meteorite|Revelstoke]] || 1965 || Canada || 1.6g || <ref>{{cite journal |last1=Folinsbee |first1=R. E. |last2=Douglas |first2=J. A. V. |date=1967 |title=Revelstoke, a new Type I carbonaceous chondrite |journal=Geochim. Cosmochim. Acta |volume=31 |pages=1625-35 }}</ref>
 |}
@@ Line 58: / Line 58: @@
 === Chemistry- Solar (System) Reference Standard===
+{{main|Abundance of the chemical elements}}
-The defining feature of CI meteorites is their chemical composition, rich in volatile elements- richer than any other meteorites. The element assay of CI meteorite is used as a geochemical standard, as it has "a remarkably close relationship"<ref>{{cite journal |last1=Holweger |first1=H. |title=The solar Na/Ca and S/Ca ratios: A close comparison with carbonaceous chondrites |journal=Earth and Planetary Science Letters |date=1977 |volume=34 |pages=152−54}}</ref> to the makeup of the [[Sun]] and greater [[Solar System]].<ref>{{cite journal |last1=Asplund |first1=M. |last2=Grevesse |first2=N. |last3=Sauval |first3=A. J. |last4=Scott |first4=P. |title=The chemical composition of the Sun |journal=Annual Review of Astronomy and Astrophysics |date=2009 |volume=47 |pages=481−522}}</ref><ref>{{cite book |last1=Palme |first1=H. |last2=Lodders |first2=K. |last3=Jones A. |title=Treatise on Geochemistry |date=2014 |publisher=Elsevier |editor=Davis, A. M. |chapter=Solar system abundances of the elements |pages=15−36}}</ref> This abundance standard is the measure by which other meteorites,<ref>{{cite journal |last1=Arndt |first1=P. |last2=Bohsung |first2=J. |last3=Maetz |first3=M. |last4=Jessberger |first4=E. K. |title=The elemental abundances in interplanetary dust particles |journal=Meteoritics & Planetary Science |date=1996 |volume=31 |issue=6 |pages=817−33}}</ref><ref name=lfs>{{cite book |last1=Lodders |first1=K. |last2=Fegley |first2=B. Jr. |title=Chemistry of the Solar System |date=2011 |publisher=RSC Publishing |location=Cambridge |isbn=978-0-85404-128-2}}</ref><ref>{{cite journal |last1=Russell |first1=S. S. |last2=Suttle |first2=M. D. |last3=King |first3=A. J. |title=Abundance and importance of petrological type 1 chondritic material |journal=Meteorit Planet Sci |date=2021 |url=https://onlinelibrary.wiley.com/doi/10.1111/maps.13753}}</ref> comets,<ref name="angr89" /><ref name="lfc" /><ref>{{cite book |last1=Lewis |first1=J. S. |title=Comet and Asteroid Impact Hazards on a Populated Earth |date=2000 |publisher=Academic Press |location=San Diego |isbn=0-12-446760-1 |page=50}}</ref><ref>{{cite journal |last1=Paquette |first1=J. A. |last2=Engrand |first2=C. |last3=Stenzel |first3=O. |last4=Hilchenbach |first4=M. |last5=Kissel |first5=J. |display-authors=etal |title=Searching for calcium-aluminum-rich inclusions in cometary particles with Rosetta/COSIMA |journal=Meteorit Planet Sci |date=2016 |volume=51 |issue=7 |pages=1340−52 |doi=10.1111/maps.12669}}</ref> and in some cases the planets themselves<ref>{{cite journal |last1=Harkins |first1=W. D. |title=The Evolution of the Elements and the Stability of Complex atoms. I. A new periodic system which shows a relation between the abundance of the elements and the structure of the nuclei of atoms. |journal=J. Am. Chem. Soc. |date=1917 |volume=39 |issue=5 |page=856}}</ref><ref>{{cite journal |last1=Morgan |first1=J. W. |last2=Anders |first2=E. |title=Chemical composition of Mars |journal=Geochim. Cosmochim. Acta |date=1979 |volume=43 |pages=1601−10}}</ref><ref>{{cite journal |last1=Dreibus |first1=G. |last2=Wanke |first2=H. |title=Mars, a volatile-rich planet |journal=Meteoritics |date=1985 |volume=20 |pages=367−81}}</ref><ref name="lfc" /> (since [[Enstatite chondrite|revised]]<ref>{{cite journal |last1=Warren |first1=P. H. |title=Stable-isotope anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for cabonaceous chondrites |journal=Earth Planet. Sci. Lett. |date=2011 |volume=311 |pages=93−100}}</ref><ref name="pz21" />) are assayed.
+The defining feature of CI meteorites is their chemical composition, rich in volatile elements- richer than any other meteorites. The element assay of CI meteorite is used as a geochemical standard, as it has "a remarkably close relationship"<ref>{{cite journal |last1=Holweger |first1=H. |title=The solar Na/Ca and S/Ca ratios: A close comparison with carbonaceous chondrites |journal=Earth and Planetary Science Letters |date=1977 |volume=34 |pages=152−54}}</ref> to the makeup of the [[Sun]] and greater [[Solar System]].<ref>{{cite journal |last1=Asplund |first1=M. |last2=Grevesse |first2=N. |last3=Sauval |first3=A. J. |last4=Scott |first4=P. |title=The chemical composition of the Sun |journal=Annual Review of Astronomy and Astrophysics |date=2009 |volume=47 |pages=481−522}}</ref><ref>{{cite book |last1=Palme |first1=H. |last2=Lodders |first2=K. |last3=Jones A. |title=Treatise on Geochemistry |date=2014 |publisher=Elsevier |editor=Davis, A. M. |chapter=Solar system abundances of the elements |pages=15−36}}</ref> This abundance standard is the measure by which other meteorites,<ref name="abmj06">{{cite journal |last1=Arndt |first1=P. |last2=Bohsung |first2=J. |last3=Maetz |first3=M. |last4=Jessberger |first4=E. K. |title=The elemental abundances in interplanetary dust particles |journal=Meteoritics & Planetary Science |date=1996 |volume=31 |issue=6 |pages=817−33}}</ref><ref name=lfs>{{cite book |last1=Lodders |first1=K. |last2=Fegley |first2=B. Jr. |title=Chemistry of the Solar System |date=2011 |publisher=RSC Publishing |location=Cambridge |isbn=978-0-85404-128-2}}</ref><ref name="rsk21">{{cite journal |last1=Russell |first1=S. S. |last2=Suttle |first2=M. D. |last3=King |first3=A. J. |title=Abundance and importance of petrological type 1 chondritic material |journal=Meteorit Planet Sci |date=2021 |url=https://onlinelibrary.wiley.com/doi/10.1111/maps.13753}}</ref> comets,<ref name="angr89" /><ref name="lfc" /><ref>{{cite book |last1=Lewis |first1=J. S. |title=Comet and Asteroid Impact Hazards on a Populated Earth |date=2000 |publisher=Academic Press |location=San Diego |isbn=0-12-446760-1 |page=50}}</ref><ref>{{cite journal |last1=Paquette |first1=J. A. |last2=Engrand |first2=C. |last3=Stenzel |first3=O. |last4=Hilchenbach |first4=M. |last5=Kissel |first5=J. |display-authors=etal |title=Searching for calcium-aluminum-rich inclusions in cometary particles with Rosetta/COSIMA |journal=Meteorit Planet Sci |date=2016 |volume=51 |issue=7 |pages=1340−52 |doi=10.1111/maps.12669}}</ref> and in some cases the planets themselves<ref>{{cite journal |last1=Harkins |first1=W. D. |title=The Evolution of the Elements and the Stability of Complex atoms. I. A new periodic system which shows a relation between the abundance of the elements and the structure of the nuclei of atoms. |journal=J. Am. Chem. Soc. |date=1917 |volume=39 |issue=5 |page=856}}</ref><ref>{{cite journal |last1=Morgan |first1=J. W. |last2=Anders |first2=E. |title=Chemical composition of Mars |journal=Geochim. Cosmochim. Acta |date=1979 |volume=43 |pages=1601−10}}</ref><ref>{{cite journal |last1=Dreibus |first1=G. |last2=Wanke |first2=H. |title=Mars, a volatile-rich planet |journal=Meteoritics |date=1985 |volume=20 |pages=367−81}}</ref><ref name="lfc" /> (since [[Enstatite chondrite|revised]]<ref>{{cite journal |last1=Warren |first1=P. H. |title=Stable-isotope anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for cabonaceous chondrites |journal=Earth Planet. Sci. Lett. |date=2011 |volume=311 |pages=93−100}}</ref><ref name="pz21" />) are assayed.
 [[Victor Goldschmidt|Goldschmidt]] noted the primitive (pre-[[Planetary differentiation|differentiated]]) compositions of some meteorites, calling it the "cosmic" abundance- he assumed meteorites had arrived from free space, not our Solar System.<ref>{{cite book |last1=Goldschmidt |first1=V. M. |title=Skrifter Norske Videnskaps: Geochemische Verteilungsgesetze der Elemente |date=1938 |publisher=Dybwad |location=Oslo}}</ref><ref>{{cite book |last1=Goldschmidt |first1=V. M. |title=Geochemistry |date=1954 |publisher=Clarendon Press |location=Oxford}}</ref> In turn, the study of such abundances stimulated- then validated- work in nucleosynthesis and stellar physics.<ref name="gs98" /><ref name="lfs" /> In a sense, Goldschmidt's choice of terms may have been borne out: both Solar and CI compositions appear similar to nearby stars as well,<ref name="howell">{{cite journal |last1=Anders |first1=E. |title=How well do we know "Cosmic" abundances? |journal=Geochim. Cosmochim. Acta |date=1971 |volume=35 |page=516}}</ref><ref name="agss09">{{cite journal |last1=Asplund |first1=M. |last2=Grevesse |first2=N. |last3=Sauval |first3=A. J. |last4=Scott |first4=P. |title=The Chemical Composition of the Sun |journal=Annu. Rev. Astron. Astrophys. |date=2009 |volume=47 |pages=481−522}}</ref> and [[presolar grains]] exist (though too small to be relevant here).
@@ Line 65: / Line 66: @@
 Issues with CI abundances include heterogeneity (local variation),<ref>{{cite journal |last1=Ebihara |first1=M. |last2=Wolf |first2=R. |last3=Anders |first3=E. |title=Are C1 chondrites chemically fractionated? A trace element study |journal=Geochim. Cosmochim. Acta |date=1982 |volume=46 |pages=1849−62}}</ref><ref>{{cite journal |last1=Barrat |first1=J. A. |last2=Zanda |first2=B. |last3=Moynier |first3=F. |last4=Bollinger |first4=C. |last5=Liorzou |first5=C. |last6=Bayon |first6=G. |title=Geochemistry of CI chondrites: Major and trace elements, and Cu and Zn isotopes |journal=Geochim. Cosmochim. Acta |date=2012 |volume=83 |pages=79−92}}</ref> and bromine and other halogens, which are water-soluble and thus labile.<ref name=andebih82>{{cite journal |last1=Anders |first1=E. |last2=Ebihara |first2=M. |title=Solar-system abundances of the elements |journal=Geochim. Cosmochim. Acta |date=1982 |volume=46 |pages=2363−80}}</ref><ref name="angr89" /><ref>{{cite journal |last1=Burnett |first1=D. S. |last2=Woolum |first2=D. S. |last3=Benjamin |first3=T. M. |last4=Rogers |first4=P. S. Z. |last5=Duffy |first5=C. J. |last6=Maggiore |first6=C. |title=A Test of the Smoothness of the Elemental Abundances of Carbonaceous Chondrites |journal=Geochim. Cosmochim. Acta |date=1989 |volume=53 |page=471}}</ref><ref name="pz21" >{{cite journal |last1=Palme |first1=H. |last2=Zipfel |first2=J. |title=The composition of CI chondrites and their contents of chlorine and bromine: Results from instrumental neutron activation analysis |journal=Meteorit. Planet Sci. |date=2021 |doi=10.1111/maps.13720}}</ref> Volatiles, such as noble gases (though see below) and the [[Goldschmidt classification|atmophile elements]] carbon, nitrogen, oxygen, etc. are lost from minerals and not assumed to hold the Solar correspondence. However, in the modern era the Solar carbon and oxygen measurements have come down significantly.<ref name=gs98>{{cite journal |last1=Grevesse |first1=N. |last2=Sauval |first2=J. |title=Standard Solar Composition |journal=Space Science Review |date=1998 |volume=85 |pages=161−74}}</ref><ref>{{cite journal |last1=Allende Prieto |first1=C. |last2=Lambert |first2=D. L. |last3=Asplund |first3=M. |title=The Forbidden Abundance of Oxygen In The Sun |journal=Astroph. J. |date=2001 |volume=556 |pages=L63−66}}</ref><ref name="lo3" >{{cite journal |last1=Lodders |first1=K. |title=Solar system abundances and condensation temperatures of the elements |journal=Astroph. J. |date=2003 |volume=591 |pages=1220−47}}</ref> As these are the two most abundant elements after hydrogen and helium, the Sun's metallicity is affected significantly.<ref name="lo3" /><ref>{{cite book |last1=Allende Prieto |first1=C. |title=14th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun |date=2008 |publisher=Astronomical Society of the Pacific |editor=van Belle, G. |isbn=978-1-58381-331-7 |chapter=The Abundances of Oxygen and Carbon in the Solar Photosphere }}</ref> It is possible that CI chondrites may hold ''too many'' volatiles, and the matrix of [[CM chondrite]]s (excluding [[chondrules]], [[calcium–aluminium-rich inclusion]]s, etc.), or bulk Tagish Lake, may be a better proxy for the Solar abundance.<ref name="andebih82" /><ref>{{cite journal |last1=Buseck |first1=P. Hua X. |title=Matrices Of Carbonaceous Chondrite Meteorites |journal=Annu. Rev. Earth Planet. Sci. |date=1993 |volume=21 |pages=255–305 |doi=10.1146/annurev.ea.21.050193.001351}}</ref><ref name=aag21>{{cite journal |last1=Asplund |first1=M. |last2=Amarsi |first2=A. M. |last3=Grevesse |first3=N. |title=The chemical make-up of the Sun: A 2020 vision |journal=Astron. Astrophys. |date=2021 |volume=653 |page=A141}}</ref>
+{{See also|Advanced Composition Explorer}}
+{{See also|Genesis_(spacecraft)}}
 ====Oxygen====
-Oxygen is the chief element in CI- and many other- meteorites. Despite the Solar agreement, the [[Abundance of the chemical elements|common elements]] carbon and nitrogen rarely condense into minerals for inclusion and recovery as meteorites. Instead, they tend to form various gases, and were depleted in the early eras of the Solar System, while oxygen forms numerous oxides.
+Oxygen is the chief element in CI- and many other- meteorites. Despite the Solar agreement, the [[Abundance of the chemical elements|common elements]] carbon and nitrogen rarely condense into minerals for inclusion and recovery as meteorites. Instead, they tend to form various gases. They were depleted in the early eras of the Solar System, while oxygen forms numerous oxides.
-[[Isotopes of oxygen|Oxygen isotope]] studies had been performed before the modern era, both on Earth rocks and meteorites.<ref>{{cite journal |last1=Vinogradov |first1=A. P. |last2=Dontsova |first2=E. I. |last3=Chupakhin |first3=M. S. |title=Isotope ratios of oxygen in meteorites and igneous rocks |journal=Geochim. Cosmochim. Acta |date=1960 |volume=18 |page=278}}</ref><ref>{{cite journal |last1=Taylor |first1=H. P. jr. |last2=Duke |first2=M. B. |last3=Silver |first3=L.T. |last4=Epstein |first4=S. |title=Oxygen isotope studies of minerals in stony meteorites |journal=Geochim. Cosmochim. Acta |date=1965 |volume=29 |pages=489−512}}</ref> However, isotope differences in individual samples (excepting radiosotopes) had once been widely held to be local effects, caused by [[Environmental isotopes|separation processes]] (plus [[Spallation#Nuclear spallation|spallation]], captures, etc.)- the materials had nevertheless all formed from a common pool, with a single oxygen mixture. The fall and analysis of the [[Allende meteorite]], with large amounts of material available for study, demonstrated clearly that the Solar System contained different oxygen reservoirs, with different isotope ratios.<ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Grossman |first2=L. |last3=Mayeda |first3=T. K. |title=A Component of Primitive Nuclear Composition in. Carbonaceous Meteorites |journal=Science |date=2 Nov 1973 |volume=182 |issue=4111 |page=485}}</ref><ref name="pmea20">{{cite journal |last1=Piralla |first1=M. |first2=Marrocchi Y. |last3=Verdier-Paoletti M. J. |last4=Vacher L. |last5=Villeneuve J. |last6=Piani L. |last7=Bekaert D. V. |last8=Gounelle M. |title=Primitive water and dust of the Solar System: Insights from in situ oxygen measurements of CI chondrites |journal=Geochim. Cosmochim. Acta |volume=269 |pages=451−64}}</ref>
+[[Isotopes of oxygen|Oxygen isotope]] studies had been performed before the modern era, both on Earth rocks and meteorites.<ref>{{cite journal |last1=Vinogradov |first1=A. P. |last2=Dontsova |first2=E. I. |last3=Chupakhin |first3=M. S. |title=Isotope ratios of oxygen in meteorites and igneous rocks |journal=Geochim. Cosmochim. Acta |date=1960 |volume=18 |page=278}}</ref><ref>{{cite journal |last1=Taylor |first1=H. P. jr. |last2=Duke |first2=M. B. |last3=Silver |first3=L.T. |last4=Epstein |first4=S. |title=Oxygen isotope studies of minerals in stony meteorites |journal=Geochim. Cosmochim. Acta |date=1965 |volume=29 |pages=489−512}}</ref> However, isotope differences in individual samples (excepting radiosotopes) had once been widely held to be local effects, caused by [[Environmental isotopes|separation processes]] (plus [[Spallation#Nuclear spallation|spallation]], captures, etc.)- the materials had nevertheless all formed from a common pool, with a single oxygen mixture. The fall and analysis of the [[Allende meteorite]], with large amounts of material available for study, demonstrated clearly that the Solar System contained different oxygen reservoirs, with different isotope ratios.<ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Grossman |first2=L. |last3=Mayeda |first3=T. K. |title=A Component of Primitive Nuclear Composition in. Carbonaceous Meteorites |journal=Science |date=2 Nov 1973 |volume=182 |issue=4111 |page=485}}</ref><ref name="pmea20">{{cite journal |last1=Piralla |first1=M. |last2=Marrocchi |first2=Y. |last3=Verdier-Paoletti M. J. |last4=Vacher L. |last5=Villeneuve J. |last6=Piani L. |last7=Bekaert D. V. |last8=Gounelle M. |title=Primitive water and dust of the Solar System: Insights from in situ oxygen measurements of CI chondrites |journal=Geochim. Cosmochim. Acta |volume=269 |pages=451−64}}</ref>
-The three stable O-isotopes are <sup>16</sup>O, <sup>17</sup>O, and <sup>18</sup>O. A "three-isotope plot" (<sup>17</sup>O/<sup>16</sup>O axis versus <sup>18</sup>O/<sup>16</sup>O axis) shows different Solar System materials- and thus, their oxygen reservoirs and formation regions- in different fields. The CI chondrites are clearly distinguished isotopically from their petrological kin, the CM chondrites, by their field: CIs are enriched in <sup>18</sup>O, and to a lesser extent <sup>17</sup>O, compared to CMs, with no overlap between them. The Antarctic (CI, CI-like, CY) meteorites are even more enriched in <sup>18</sup>O. These are the heaviest-oxygen materials in the Solar System. Oxygen isotope studies and classification have gone on to other meteorite groups, classes, and more astromaterials.<ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Onuma |first2=N. |last3=Mayeda |first3=T. K. |title=A classification of meteorites based on oxygen isotopes |journal=Earth Planet.Sci. Lett. |date=1976 |volume=30 |pages=10−18}}</ref><ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Mayeda |first2=T. K. |title=The oxygen isotope record in Murchison and other carbonaceous chondrites |journal=Earth Planet. Sci. Lett. |date=1984 |volume=67 |pages=151−61}}</ref><ref>{{cite book |title=Oxygen in the Solar System |date=2008 |publisher=Mineralogical Society of America |location=Chantilly, VA |editor=MacPherson, Glenn J.|isbn=978-0-939950-80-5}}</ref><ref name="ip93" /><ref name="pmea20" />
+The three stable O-isotopes are [[Oxygen-16|<sup>16</sup>O]], [[Oxygen-17|<sup>17</sup>O]], and [[Oxygen-18|<sup>18</sup>O]]. A "three-isotope plot" (<sup>17</sup>O/<sup>16</sup>O axis versus <sup>18</sup>O/<sup>16</sup>O axis) shows different Solar System materials- and thus, their oxygen reservoirs and likely, different formation regions- in different fields. The CI chondrites are clearly distinguished isotopically from their petrological kin, the CM chondrites, by their field: CIs are enriched in <sup>18</sup>O, and to a lesser extent <sup>17</sup>O, compared to CMs, with no overlap between them. The Antarctic (CI, CI-like, and/or CY) meteorites are even more enriched in <sup>18</sup>O. These are the macroscopic samples with the heaviest oxygen in the Solar System. Oxygen isotope studies and classification have gone on to other meteorite groups, classes, and more astromaterials.<ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Onuma |first2=N. |last3=Mayeda |first3=T. K. |title=A classification of meteorites based on oxygen isotopes |journal=Earth Planet.Sci. Lett. |date=1976 |volume=30 |pages=10−18}}</ref><ref>{{cite journal |last1=Clayton |first1=R. N. |last2=Mayeda |first2=T. K. |title=The oxygen isotope record in Murchison and other carbonaceous chondrites |journal=Earth Planet. Sci. Lett. |date=1984 |volume=67 |pages=151−61}}</ref><ref>{{cite book |title=Oxygen in the Solar System |date=2008 |publisher=Mineralogical Society of America |location=Chantilly, VA |editor=MacPherson, Glenn J.|isbn=978-0-939950-80-5}}</ref><ref name="ip93" /><ref name="pmea20" />
 ====Iron====
-Iron is present with 25 weight %, but mainly in phyllosilicates and [[oxidation|oxidised]] form (magnetite)- see below. This is a marginally higher level than CM chondrites, as iron is somewhat cooler-forming than magnesium. The [[Siderophile element|siderophiles]] nickel and cobalt follow iron as well.<ref>{{cite journal |last1=Kallemeyn |first1=G. |last2=Wasson |first2=J. |title=The compositional classification of chondrites−I. The carbonaceous chondrite groups |journal=Geochim. Cosmochim. Acta |date=1981 |volume=45 |issue=7 |page=1217 |doi=10.1016/0016-7037(81)90145-9}}</ref>
+Iron is present with 25 weight %, but mainly compounded in phyllosilicates and [[oxides]] (magnetite)- see below. This is a marginally higher level than CM chondrites, as iron is somewhat cooler-forming than magnesium. The [[Siderophile element|siderophiles]] nickel and cobalt follow iron as well.<ref>{{cite journal |last1=Kallemeyn |first1=G. |last2=Wasson |first2=J. |title=The compositional classification of chondrites−I. The carbonaceous chondrite groups |journal=Geochim. Cosmochim. Acta |date=1981 |volume=45 |issue=7 |page=1217 |doi=10.1016/0016-7037(81)90145-9}}</ref>
 The majority of the iron is in the form of cations in the phyllosilicates and iron bound as magnetite. Some  appears as [[ferrihydrite]],<ref name="tb88"/> but not in Ivuna.<ref name="b92" />
 ====Carbon====
-CIs average ~3.8% carbon, with excursions from 2-5%. This is the highest of the carbonaceous chondrites, but not of all meteorites- [[ureilite]]s may contain more.
+CIs average ~3.8% carbon, with excursions from 2-5%. This is the highest of the carbonaceous chondrites, but not of all meteorites- some [[ureilite]]s may contain more.
-The carbon is in the form of native carbon (graphite, nanodiamonds, etc.), and carbonates,<ref>{{cite journal |last1=DuFresne |first1=E. R. |last2=Anders |first2=E. |title=On the chemical evolution of the carbonaceous chondrites |journal=Geochim. Cosmochim. Acta |date=1962 |volume=26 |pages=1085−1114}}</ref><ref>{{cite journal |last1=Richardson |first1=S. M. |title=Vein formation in the C1 carbonaceous chondrites |journal=Meteoritics |date=1978 |volume=13 |issue=1 |page=141}}</ref> but the bulk is as organics.
+The carbon is in the form of native carbon (graphite, nanodiamonds, etc.), and carbonates,<ref>{{cite journal |last1=DuFresne |first1=E. R. |last2=Anders |first2=E. |title=On the chemical evolution of the carbonaceous chondrites |journal=Geochim. Cosmochim. Acta |date=1962 |volume=26 |pages=1085−1114}}</ref><ref>{{cite journal |last1=Richardson |first1=S. M. |title=Vein formation in the C1 carbonaceous chondrites |journal=Meteoritics |date=1978 |volume=13 |issue=1 |page=141}}</ref> but the bulk is dispersed as globules of organics.
-Organics in CIs include a lesser amount of soluble fractions, and a majority of macromolecular (insoluble) organics such as PAHs.
+Organics in CIs include a lesser amount of soluble fractions, and a majority of macromolecular (insoluble) organics such as [[Polycyclic_aromatic_hydrocarbons|PAHs]].
 ====Gas====
@@ Line 88: / Line 90: @@
 {{ main | Gas-rich meteorites }}
-All carbonaceous meteorites are, to some extent, gas-rich.<ref>{{cite journal |last1=Mazor E. |last2=Heymann D. Anders E. |title=Noble gases in carbonaceous chondrites |date=1970 |journal=Geochim. Cosmochim. Acta |volume=34 |pages=781-24 }}</ref><ref name="wmtressh">{{cite book |last1= Wasson J. |title=Meteorites: Their Record of Early Solar System History |date=1985 }}</ref><ref name="ad75" /> Orgueil,<ref>{{cite journal |last1=Frick U. |last2=Moniot R. K. |title=Noble gases in ca residue from the Orgueil and Murray Met |date=1976 |journal=Meteoritics |volume=11 |pages=281 }}</ref><ref name="lo3" /> Alais, Ivuna<ref>{{cite journal |last1=Black D. C. |title=On the origins of trapped helium, neon and argon isotope variations in meteorites-II. Carbonaceous meteorites |date=1972 |journal=Geochim. Cosmochim. Acta |volume=36 3 |pages=377-94 }}</ref> and Tonk all assay to higher gas levels than typical meteorites- Revelstoke is too small for measurement.<ref>{{cite journal |last1=Goswami J. N. |last2=Lal D. |last3=Wilkening L. L. |title=Gas-rich meteorites − probes for particle environments and dynamic processes in the inner solar system |date=1984 |journal=Space Sci. Rev. |volume=37 |pages=111-59 }}</ref><ref>{{cite journal |last1=Schultz L. |last2=Franke L. |title=Helium, neon, and argon in meteorites: A data collection |date=2010 |journal=Meteorit. Planet. Sci. |volume=39 |issue=11 |pages=1889-90 |url=maps83-sup-0002-si.pdf }}</ref>
+All carbonaceous meteorites are, to some extent, gas-rich.<ref>{{cite journal |last1=Mazor E. |last2=Heymann D. Anders E. |title=Noble gases in carbonaceous chondrites |date=1970 |journal=Geochim. Cosmochim. Acta |volume=34 |pages=781-24 }}</ref><ref name="wmtressh">{{cite book |last1= Wasson J. |title=Meteorites: Their Record of Early Solar System History |date=1985 }}</ref><ref name="ad75" /> Orgueil,<ref>{{cite journal |last1=Frick U. |last2=Moniot R. K. |title=Noble gases in ca residue from the Orgueil and Murray Met |date=1976 |journal=Meteoritics |volume=11 |pages=281 }}</ref><ref name="lo3" /> Alais, Ivuna<ref>{{cite journal |last1=Black D. C. |title=On the origins of trapped helium, neon and argon isotope variations in meteorites-II. Carbonaceous meteorites |date=1972 |journal=Geochim. Cosmochim. Acta |volume=36 3 |pages=377-94 }}</ref> and Tonk all assay to higher gas levels than typical meteorites-<ref>{{cite journal |last1=Goswami J. N. |last2=Lal D. |last3=Wilkening L. L. |title=Gas-rich meteorites − probes for particle environments and dynamic processes in the inner solar system |date=1984 |journal=Space Sci. Rev. |volume=37 |pages=111-59 }}</ref> Revelstoke is too small for traditional measurements.<ref>{{cite journal |last1=Schultz L. |last2=Franke L. |title=Helium, neon, and argon in meteorites: A data collection |date=2010 |journal=Meteorit. Planet. Sci. |volume=39 |issue=11 |pages=1889-90 |url=https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fj.1945-5100.2004.tb00083.x&file=maps83-sup-0002-si.pdf }}</ref><ref name="rsk21" />
-in carbon "dark" CM-like<ref name="wmtressh" /> "an extraordinary absorber", and magnetite<ref>{{cite journal |last1=Fanale F. P. |last2=Cannon W. A. |title=Surface properties of the Orgueil met: implications for the early history of sol sys volatiles |date=1974 |journal=Geochim. Cosmochim. Acta |volume=38 |pages=453 }}</ref><ref name="la75" />
+Most gases store mostly in carbon. Carbon's [[Allotropes of carbon|numerous allotropes]] form numerous network solids, able to store atoms in their lattices. Gases are often found in "dark" CM-like deposits,<ref name="wmtressh" /> "an extraordinary absorber", and in magnetite<ref>{{cite journal |last1=Fanale F. P. |last2=Cannon W. A. |title=Surface properties of the Orgueil met: implications for the early history of sol sys volatiles |date=1974 |journal=Geochim. Cosmochim. Acta |volume=38 |pages=453 }}</ref><ref name="la75" />
@@ Line 102: / Line 104: @@
 {{main|Silicate_mineral#Phyllosilicates}}
-Though CM chondrites also have large amounts of phyllosilicates,<ref>{{cite journal |last1=Calvin |first1=W. M. |last2=King |first2=T. V. V. |title=Spectral characteristics of iron-bearing phyllosilicates: Comparison to Orgueil (CI1), Murchison and Murray (CM2) |journal=Meteorit. Planet Sci. |date=1997 |volume=32 |pages=693−701}}</ref><ref name="mcsr77">{{cite journal |last1=McSween |first1=H. Y. Jr. |last2=Richardson |first2=S. M. |title=The composition of carbonaceous chondrite matrix |journal=Geochim. Cosmochim. Acta |date=1977 |volume=41 |pages=1145−61}}</ref> CI chondrites are distinguished by a near-absence of anything ''but'' phyllosilicate matrix, per their Type 1 petrographic designation.<ref>{{cite journal |last1=Larimer |first1=J. W. |last2=Anders |first2=E. |title=Chemical fractionations in meteorites−III. Major element fractionations in chondrites |journal=Geochim. Cosmochim. Acta |date=1970 |volume=34 |pages=367−87}}</ref><ref name="bp92">{{cite journal |last1=Brearley A. J. |last2=Prinz M. |title=CI chondrite-like clasts in the Nilpena polymict ureilite: Implications for aqueous alteration processes in CI chondrites |date=1993 |journal=Geochim. Cosmochim. Acta |volume=56 |pages=1373-86 }}</ref> CMs are predominantly [[tochilinite]]-[[cronstedtite]] intergrowths ("TCI"), while CIs hold [[serpentinite]]-smectite (often [[saponite]]) layers.<ref>{{cite journal |last1=Bass |first1=M. N. |title=Montmorillonite and serpentine in Orgueil meteorite |journal=Geochim. Cosmochim. Acta |date=1971 |volume=35 |pages=139−47}}</ref><ref name="tb88">{{cite journal |last1=Tomeoka |first1=K. |last2=Buseck |first2=P. R. |title=Matrix mineralogy of the Orgueil CI carbonaceous chondrite |journal=Geochim. Cosmochim. Acta |date=1988 |volume=52 |pages=1627−40}}</ref><ref name="b92">{{cite conference|last1=Brearley |first1=A. J. |title=Mineralogy of fine grained matrix in the Ivuna CI carbonaceous chondrite |conference=LPS XXIII |date=1992 |page=153}}</ref><ref name="ktm2">{{cite journal |last1=Keller L. P. |last2=Thomas K. L. |last3=McKay D. S. |title=An interplanetary dust particle with links to CI chondrites |date=1992 |journal=Geochim. Cosmochim. Acta |volume=56 |pages=1409-12 }}</ref> In both cases, the two minerals form sheets alternating at the molecular level; the phyllosilicate then holds hydroxide ions (OH<sup>-</sup>) or true water (H<sub>2</sub>O) bound between layers (possibly both, in the case of [[multilayer]]s).<ref>{{cite journal |last1=Beck |first1=P. |last2=Quirico |first2=E. |last3=Montes-Hernandez |first3=G. |last4=Bonal |first4=L. |last5=Bollard |first5=J. |last6=Orthous-Daunay F.-R. |last7=Howard K. T. |last8=Schmitt B. |last9=Brissaud O.|last10= Deschamps F. |last11=Wunder B. |last12=Guillot S. |title=Hydrous mineralogy of CM and CI chondrites from infrared spectroscopy and their relationship with low albedo asteroids |journal=Geochim. Cosmochim. Acta |date=2010 |volume=74 |pages=4881−92}}</ref> Serpentinite and saponite were identified by their characteristic 7-Angstrom and ~12-Angstrom sheet spacings, respectively.<ref name="aka8" /><ref name=b92 /><ref name="kshr15">{{cite journal |last1=King |first1=A. J. |last2=Schofield |first2=P. F. |last3=Howard |first3=K. T. |last4=Russell |first4=S.S. |title=Modal mineralogy of CI and CI-like chondrites by X-ray diffraction |journal=Geochim. Cosmochim. Acta |date=2015 |volume=165 |pages=148−60}}</ref>
+Though CM chondrites also have large amounts of phyllosilicates,<ref>{{cite journal |last1=Calvin |first1=W. M. |last2=King |first2=T. V. V. |title=Spectral characteristics of iron-bearing phyllosilicates: Comparison to Orgueil (CI1), Murchison and Murray (CM2) |journal=Meteorit. Planet Sci. |date=1997 |volume=32 |pages=693−701}}</ref><ref name="mcsr77">{{cite journal |last1=McSween |first1=H. Y. Jr. |last2=Richardson |first2=S. M. |title=The composition of carbonaceous chondrite matrix |journal=Geochim. Cosmochim. Acta |date=1977 |volume=41 |pages=1145−61}}</ref> CI chondrites are distinguished petrologically by a near-absence of anything ''but'' phyllosilicate matrix, per their Type 1 designation.<ref>{{cite journal |last1=Larimer |first1=J. W. |last2=Anders |first2=E. |title=Chemical fractionations in meteorites−III. Major element fractionations in chondrites |journal=Geochim. Cosmochim. Acta |date=1970 |volume=34 |pages=367−87}}</ref><ref name="bp92">{{cite journal |last1=Brearley A. J. |last2=Prinz M. |title=CI chondrite-like clasts in the Nilpena polymict ureilite: Implications for aqueous alteration processes in CI chondrites |date=1993 |journal=Geochim. Cosmochim. Acta |volume=56 |pages=1373-86 }}</ref> CMs are predominantly [[tochilinite]]-[[cronstedtite]] intergrowths ("TCI"), while CIs hold [[serpentinite]]-smectite (often [[saponite]]) layers.<ref>{{cite journal |last1=Bass |first1=M. N. |title=Montmorillonite and serpentine in Orgueil meteorite |journal=Geochim. Cosmochim. Acta |date=1971 |volume=35 |pages=139−47}}</ref><ref name="tb88">{{cite journal |last1=Tomeoka |first1=K. |last2=Buseck |first2=P. R. |title=Matrix mineralogy of the Orgueil CI carbonaceous chondrite |journal=Geochim. Cosmochim. Acta |date=1988 |volume=52 |pages=1627−40}}</ref><ref name="b92">{{cite conference|last1=Brearley |first1=A. J. |title=Mineralogy of fine grained matrix in the Ivuna CI carbonaceous chondrite |conference=LPS XXIII |date=1992 |page=153}}</ref><ref name="ktm2">{{cite journal |last1=Keller L. P. |last2=Thomas K. L. |last3=McKay D. S. |title=An interplanetary dust particle with links to CI chondrites |date=1992 |journal=Geochim. Cosmochim. Acta |volume=56 |pages=1409-12 }}</ref> In both cases, the two minerals form sheets alternating at the molecular level; the phyllosilicate then holds hydroxide ions (OH<sup>-</sup>) or true water (H<sub>2</sub>O) bound between layers (possibly both, in the case of [[multilayer]]s).<ref>{{cite journal |last1=Beck |first1=P. |last2=Quirico |first2=E. |last3=Montes-Hernandez |first3=G. |last4=Bonal |first4=L. |last5=Bollard |first5=J. |last6=Orthous-Daunay F.-R. |last7=Howard K. T. |last8=Schmitt B. |last9=Brissaud O.|last10= Deschamps F. |last11=Wunder B. |last12=Guillot S. |title=Hydrous mineralogy of CM and CI chondrites from infrared spectroscopy and their relationship with low albedo asteroids |journal=Geochim. Cosmochim. Acta |date=2010 |volume=74 |pages=4881−92}}</ref> Serpentinite and saponite were identified by their characteristic 7-Angstrom and ~12-Angstrom sheet spacings, respectively.<ref name="aka8" /><ref name=b92 /><ref name="kshr15">{{cite journal |last1=King |first1=A. J. |last2=Schofield |first2=P. F. |last3=Howard |first3=K. T. |last4=Russell |first4=S.S. |title=Modal mineralogy of CI and CI-like chondrites by X-ray diffraction |journal=Geochim. Cosmochim. Acta |date=2015 |volume=165 |pages=148−60}}</ref>
-These phyllosilicates are the products of aqueous alteration, when the original protosolar condensates olivine and pyroxene, with ionic bonds between their components, are subject to water, often with heat.<ref>{{cite journal |last1=Zolensky |first1=M. E. |last2=Bourcier |first2=W. L. |last3=Gooding |first3=J. L. |title=Aqueous alteration on the hydrous asteroids: Results of EQ3/6 computer simulation |journal=Icarus |date=1978 |volume=2 |pages=411−25}}</ref><ref>{{cite journal |last1=Zolensky |first1=M. |last2=Barrett |first2=R. |last3=Browning |first3=L. |title=Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites |journal=Geochim. |date=1993 |volume=57 |pages=3123−48}}</ref><ref>{{cite journal |last1=Jones |first1=C. L. |last2=Brearley |first2=A. J. |title=Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration |journal=Geochim. |date=2006 |volume=70 |pages=1040–1058}}</ref> The debate is whether this alteration, in general, happened at free-floating particles (the nebular hypothesis)<ref name="bischoff98">{{cite journal |last1=Bischoff |first1=A. |title=Aqueous Alteration of Carbonaceous Chondrites: Evidence for Preaccretionary Alteration |journal=Meteorit. Planet Sci. |date=1998 |volume=33 |pages=1113−22 |doi=10.1111/J.1945-5100.1998.TB01716.X}}</ref> or within meteorites (or their parent [[Small Solar System body|small bodies]])- the parent body hypothesis.<ref>{{cite journal |last1=Tomeoka |first1=K. |title=Phyllosilicate veins in a CI meteorite: evidence for aqueous alteration on the parent body |journal=Nature |date=1990 |volume=345 |pages=138−40}}</ref> On CI chondrites, the existence of veins, and multiple morphologies of magnetite, suggest possibly both, in multiple episodes.<ref name="k70">{{cite journal |last1=Kerridge J. F. |title=Some observations on the nature of magnetite in the Orgueil meteorite |date=1970 |journal=Earth Planet. Sci. Lett. |volume=9 |pages=229-306 }}</ref><ref name="tb88" /><ref name="b92" /><ref name="ip93" >{{cite journal |last1=Ikeda Y. |last2=Prinz M. |title=Petrologic study of the Belgica 7904 carbonaceous chondrite: Hydrous alteration, thermal metamorphism, and relation to CM and CI chondrites |date=1993 |journal=Geochim. Cosmochim. Acta |volume=57 |pages=439-52}}</ref><ref name="hb98" />
+These phyllosilicates are the products of aqueous alteration, when the original protosolar condensates olivine and pyroxene, with ionic bonds between their components, are subject to water, often with heating.<ref>{{cite journal |last1=Zolensky |first1=M. E. |last2=Bourcier |first2=W. L. |last3=Gooding |first3=J. L. |title=Aqueous alteration on the hydrous asteroids: Results of EQ3/6 computer simulation |journal=Icarus |date=1978 |volume=2 |pages=411−25}}</ref><ref>{{cite journal |last1=Zolensky |first1=M. |last2=Barrett |first2=R. |last3=Browning |first3=L. |title=Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites |journal=Geochim. |date=1993 |volume=57 |pages=3123−48}}</ref><ref>{{cite journal |last1=Jones |first1=C. L. |last2=Brearley |first2=A. J. |title=Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration |journal=Geochim. |date=2006 |volume=70 |pages=1040–1058}}</ref> The debate is whether this alteration, in general, happened at free-floating particles (the nebular hypothesis)<ref name="bischoff98">{{cite journal |last1=Bischoff |first1=A. |title=Aqueous Alteration of Carbonaceous Chondrites: Evidence for Preaccretionary Alteration |journal=Meteorit. Planet Sci. |date=1998 |volume=33 |pages=1113−22 |doi=10.1111/J.1945-5100.1998.TB01716.X}}</ref> or within the meteorites (or their parent [[Small Solar System body|small bodies]])- the parent body hypothesis.<ref>{{cite journal |last1=Tomeoka |first1=K. |title=Phyllosilicate veins in a CI meteorite: evidence for aqueous alteration on the parent body |journal=Nature |date=1990 |volume=345 |pages=138−40}}</ref> On CI chondrites, the existence of veins, and multiple morphologies of magnetite, suggest possibly both, in multiple episodes.<ref name="k70">{{cite journal |last1=Kerridge J. F. |title=Some observations on the nature of magnetite in the Orgueil meteorite |date=1970 |journal=Earth Planet. Sci. Lett. |volume=9 |pages=229-306 }}</ref><ref name="tb88" /><ref name="b92" /><ref name="ip93" >{{cite journal |last1=Ikeda Y. |last2=Prinz M. |title=Petrologic study of the Belgica 7904 carbonaceous chondrite: Hydrous alteration, thermal metamorphism, and relation to CM and CI chondrites |date=1993 |journal=Geochim. Cosmochim. Acta |volume=57 |pages=439-52}}</ref><ref name="hb98" />
 It is peculiar that extensively-altered material should yet have the most primitive element abundances.<ref>{{cite journal |last1=McSween |first1=H. Y. |title=Cosmic or Cosmuck? |journal=Meteoritics |date=1993 |volume=28 |page=3}}</ref> Whatever aqueous processes shaped CI chondrites either did not drive minerals farther than mm- to cm-scale, or the parent body was so thoroughly fluidized that all volumes which became the CI chondrites were homogenized-<ref name="tzlwn03" /><ref name=kshr15 /><ref name=pz21 /><ref>{{cite journal |last1=Bland P. A. |last2=Travis B. J. |title=Giant convecting mud balls of the early solar system |date=2017 |journal=Sci. Advances |volume=3 |page=7 |page=e1602514 }}</ref> in either case, a closed system.<ref name="pmea20" />
@@ Line 110: / Line 112: @@
 Aqueous alteration has proceeded toward the point of no free (metallic) metal. All or essentially all [[Meteoritic iron|metal grains]] are now bound as oxides, sulfides, etc.<ref>{{cite journal |last1=Wiik H. B. |title=The chemical composition of some stony meteorites |date=1956 |journal=Geochim. Cosmochim. Acta |volume=9 |pages=279-89}}</ref>
-In the case of Antarctic finds (the putative CY chondrites), this process has partially reversed. Phyllosilicates have, to some extents, dehydrated and reverted to silicates<ref>{{cite journal |last1=Day |first1=K. L. |title=A possible indentification of the 10 micron "silicate" feature |journal=Astrophys. J. |date=1974 |volume=192 |page=L15}}</ref><ref name="aka8">{{cite journal |last1=Akai J. |title=Incompletely transformed serpentine-type phyllosilicates in the matrix of Antarctic CM chondrites |date=1988 |journal=Geochim. Cosmochim. Acta |volume=52 |pages=1593-99 }}</ref><ref name="tzlwn03">{{cite journal |last1=Tonui |first1=E. K. |last2=Zolensky |first2=M. E. |last3=Lipschutz |first3=M. E. |last4=Wang |first4=M.-S. |last5=Nakamura |first5=T. |title=Yamato 86029: Aqueously altered and thermally metamorphosed CI-like chondrite with unusual textures |journal=Meteorit. Planet. Sci. |date=2003 |volume=38 |issue=2 |pages=269−92}}</ref><ref>{{cite journal |last1=Burton A. S. Grunsfeld S. Elsila J. E. Glavin D. P. Dworkin J. P. |title=The effects of parent-body hydrothermal heating on amino acid abundances in CI-like chondrites |date=2014 |journal=Polar Science |volume=8 |page=255 }}</ref> suggesting a different parent body for those meteorites.<ref>{{cite journal |last1=Miyamoto |first1=M. |title=Thermal metamorphism of CI and CM carbonaceous chondrites: An internal heating model |journal=Meteoritics |date=1991 |volume=26 |issue=2 |pages=111−15}}</ref>
+In the case of Antarctic finds (the putative CY chondrites), this process has partially reversed. Phyllosilicates have, to some extents, dehydrated and reverted to silicates<ref>{{cite journal |last1=Day |first1=K. L. |title=A possible identification of the 10 micron "silicate" feature |journal=Astrophys. J. |date=1974 |volume=192 |page=L15}}</ref><ref name="aka8">{{cite journal |last1=Akai J. |title=Incompletely transformed serpentine-type phyllosilicates in the matrix of Antarctic CM chondrites |date=1988 |journal=Geochim. Cosmochim. Acta |volume=52 |pages=1593-99 }}</ref><ref name="tzlwn03">{{cite journal |last1=Tonui |first1=E. K. |last2=Zolensky |first2=M. E. |last3=Lipschutz |first3=M. E. |last4=Wang |first4=M.-S. |last5=Nakamura |first5=T. |title=Yamato 86029: Aqueously altered and thermally metamorphosed CI-like chondrite with unusual textures |journal=Meteorit. Planet. Sci. |date=2003 |volume=38 |issue=2 |pages=269−92}}</ref><ref>{{cite journal |last1=Burton A. S. |last2=Grunsfeld S. |last3=Elsila J. E. |last4=Glavin D. P. |last5=Dworkin J. P. |title=The effects of parent-body hydrothermal heating on amino acid abundances in CI-like chondrites |date=2014 |journal=Polar Science |volume=8 |page=255 }}</ref> suggesting a different parent body for those meteorites.<ref>{{cite journal |last1=Miyamoto |first1=M. |title=Thermal metamorphism of CI and CM carbonaceous chondrites: An internal heating model |journal=Meteoritics |date=1991 |volume=26 |issue=2 |pages=111−15}}</ref>
+This water can be extracted artificially by thermogravimetric analysis: using heat to drive off volatiles from their storage. Temperatures vary with the form and host. In the case of hydroxide, two such ions [[Hydroxylation|hydroxylate]] each other, to give one water molecule and one oxygen molecule:<ref>{{cite conference |last1=Yoldi-Martinez |first1=Z. |last2=Beck P. |last3=Montes-Hernandez G. |last4=Chiriac R. |last5=Quirico E. |last6=Bonal L. |last7=Schmitt B. |last8=Moynier F. |title=Hydrous Mineralogy of Carbonaceous Chondrites from thermogravimetry analysis |conference=74th Meteoritical Society Meeting |date=2011 |page=5329}}</ref><ref>{{cite journal |last1=King |first1=A.J. |last2=Solomon J.R. |last3=Schofield P.F. |title=Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy |journal=EPS |date=2015 |volume=67 |page=198 |doi=10.1186/s40623-015-0370-4}}</ref><ref>{{cite journal |last1=Britt |first1=D. T. |last2=Cannon K. M. |last3=Donaldson Hanna K. |title=Simulated asteroid materials based on carbonaceous chondrite mineralogies |journal=Meteorit. Planet. Sci. |date=2019 |volume=54 |issue=9 |pages=2067–2082}}</ref>
+:2{{nbsp}}OH  →  {{nbsp}}H<sub>2</sub>O + O<sub>2</sub>
 ====Water====
-CI chondrites contain between 17 and 22 weight % water. Their high porosity (of up to 30%) seems to be correlated to that fact. The water is not occurring freely, but is rather tied up in water-bearing silicates. Strong aqueous alteration at rather low temperatures (at 50 to 150&nbsp;°C)<ref>Zolensky, M. E. & Thomas, K. L. (1995). GCA, 59, p. 4707–4712.</ref> – a hallmark of CI chondrites – is indicated by the occurrence of minerals like epsomite, but also by carbonates and sulfates. Liquid water must have penetrated the parent body through cracks and fissures and then deposited the water-bearing phases.
+CI chondrites contain between 17 and 22 weight % water. Their high porosity (of up to 30%) seems to be correlated to that fact. The water is mostly tied up in water-bearing silicates. Strong aqueous alteration at rather low temperatures (at 50 to 150&nbsp;°C)<ref>Zolensky, M. E. & Thomas, K. L. (1995). GCA, 59, p. 4707–4712.</ref> – a hallmark of CI chondrites – is indicated by the occurrence of minerals like epsomite, but also by carbonates and sulfates. Liquid water must have penetrated the parent body through cracks and fissures and then deposited the water-bearing phases.
+[[Fluid inclusions]] have been identified in other meteorites,<ref>{{cite journal |last1=Tsuchiyama |first1=A. |last2=Miyake A. |last3=Kawano J. |title=Nano-Sized CO2-H2O Fluid Inclusions in Calcite Grains of the Sutter's Mill CM Meteorite |journal=81st Meteoritical Society |date=2018 |page=6187}}</ref><ref>{{cite journal |last1=Tsuchiyama |first1=A. |last2=Miyake A. |last3=Okuzumi S. |last4=Kitayama A. |last5=Kawano J. |last6=Uesugi K. |last7=Takeuchi A. |last8=Nakano T. |last9=Zolensky M. |title=Discovery of primitive CO2-bearing fluid in an aqueously altered carbonaceous chondrite |journal=Science Advances |date=2021 |volume=7 |issue=17 |page=eabg9707 |doi=10.1126/sciadv.abg9707}}</ref> and the CI chondrites Ivuna, and likely Orgueil.<ref name="say1">{{cite conference |last1=Saylor |first1=J. |last2=Zolensky M. |last3=Bodnar R. |last4=Le L. |last5=Schwandt C. |title=Fluid Inclusions In Carbonaceous Chondrites |conference=LPS XXXII |date=2001 |page=1875}}</ref><ref>{{cite journal |last1=Zolensky |first1=M. E. |last2=Bodnar R. J. |last3=Yurimoto H. |last4=Itoh S. |last5=Fries M. |last6=Steele A. |last7=Chan Q. H.-S. |last8=Tsuchiyama A. |last9=Kebukawa Y.  |last10=Ito M. |title=The search for and analysis of direct samples of early Solar System aqueous fluids |journal=Phil. Trans. R. Soc. A |date=2017 |volume=375 |issue=2094 |page=20150386 |doi=10.1098/rsta.2015.0386}}</ref> Such brine samples are the only direct surviving fluids that can be studied from the early solar system.
 ====Magnetite====
-Elemental iron is essentially absent, converted to e. g., [[magnetite]]. Though found in many meteorites, magnetite is common and characteristic of the carbonaceous chondrites, and especially of CIs.<ref name="rahmd">{{cite journal |last1=Rahmdor |first1=P. |title=The Opaque Minerals in Stony Meteorites |journal=J. Geophys. Res |date=1963 |volume=68 |issue=7 |page=2011 }}</ref> "very common" "characteristic" }}</ref>. Magnetite abundance is ~4%, second after phyllosilicates;<ref>{{ cite journal |last1=Alfing |first1=J. |last2=Patzek |first2=M |last3=Bischoff |first3=A |title=Modal Abundances of coarse-grained (>5um) components within CI-chondrites and their individual clasts − Mixing of various lithologies on the CI parent body(ies) |journal=Geochem. |date=2019 |volume=79 |issue=4 |page=125532 }}</ref> it takes many sizes and morphologies<ref name="jedwab67" /><ref>{{cite journal |last1=Kerridge |first1=J. F. |last2=Chatterji S. |title=Magnetite Content of a Type I Carbonaceous Meteorite |date=1968 |journal=Nature |volume=220 |pages=775-76 }}</ref><ref name="j70">{{ cite journal |last1=Jedwab |first1=J. |title=La Magnetite de la Meteorite D'Orgueil Vue au Microscope Electronique a Balayage |date=1971 |journal=Icarus |volume=15 |pages=319-45}}</ref>
+Elemental iron is essentially absent, converted to e. g., [[magnetite]]. Though found in many meteorites, magnetite is common and characteristic of the carbonaceous chondrites, and especially of CIs.<ref name="rahmd">{{cite journal |last1=Rahmdor |first1=P. |title=The Opaque Minerals in Stony Meteorites |journal=J. Geophys. Res |date=1963 |volume=68 |issue=7 |page=2011 |quote="very common" "characteristic" }}</ref>. Magnetite abundance is ~4%, second after phyllosilicates;<ref>{{ cite journal |last1=Alfing |first1=J. |last2=Patzek |first2=M. |last3=Bischoff |first3=A. |title=Modal Abundances of coarse-grained (>5um) components within CI-chondrites and their individual clasts − Mixing of various lithologies on the CI parent body(ies) |journal=Geochem. |date=2019 |volume=79 |issue=4 |page=125532 }}</ref> it takes many sizes and morphologies<ref name="jedwab67" /><ref>{{cite journal |last1=Kerridge |first1=J. F. |last2=Chatterji S. |title=Magnetite Content of a Type I Carbonaceous Meteorite |date=1968 |journal=Nature |volume=220 |pages=775-76 }}</ref><ref name="j70">{{ cite journal |last1=Jedwab |first1=J. |title=La Magnetite de la Meteorite D'Orgueil Vue au Microscope Electronique a Balayage |date=1971 |journal=Icarus |volume=15 |pages=319-45}}</ref>
-These morphologies include conventional crystals, spheres and spheroids. Sphere(oids) are multiple sizes<ref name="rahmd" /><ref name="k70" /> unlike CM<ref name="la75" />{{ cite journal |last1=Lewis |first1=R. S. |last2=Anders E. |title=Condensation time of the Solar Nebula from Extinct 129I in Primitive Meteorites |date=1975 |journal=PNAS |volume=72 |issue=1 |pages=268-73 }}</ref> "Framboids" (fr. [[raspberry]]) are round clusters of round spheroids.<ref name="jedwab67" /><ref name="k70" /><ref name="hb98" >{{cite journal |last1=Hua |first1=X. |last2=Buseck P. R. |title=Unusual forms of magnetite in the Orgueil carbonaceous chondrite |date=1998 |journal=Meteorit. Planet. Sci. |volume=33 |pages=A215-20 }}</ref> "Plaquettes" resemble stacks of dishes, [[Screw thread|threads]], or beehives.<ref name="jedwab67">{{ cite journal |last1=Jedwab |first1=J. |title=La Magnetite en Plaquettes des Meteorites carbonees D'Alais, Ivuna et Orgueil |date=1967 |journal=Earth Planet. Sci. Lett. |volume=2 |pages=440-444}}</ref><ref name="j70" /><ref name="hb98" /> They are characteristic of CIs, and not found in CMs.<ref name="bp92" />
+These morphologies include conventional crystals, spheres and spheroids. Sphere(oids) are multiple sizes<ref name="rahmd" /><ref name="k70" /> unlike CM<ref name="la75" >{{ cite journal |last1=Lewis |first1=R. S. |last2=Anders E. |title=Condensation time of the Solar Nebula from Extinct 129I in Primitive Meteorites |date=1975 |journal=PNAS |volume=72 |issue=1 |pages=268-73 }}</ref> "Framboids" (fr. [[raspberry]]) are round clusters of round spheroids.<ref name="jedwab67" /><ref name="k70" /><ref name="hb98" >{{cite journal |last1=Hua |first1=X. |last2=Buseck P. R. |title=Unusual forms of magnetite in the Orgueil carbonaceous chondrite |date=1998 |journal=Meteorit. Planet. Sci. |volume=33 |pages=A215-20 }}</ref> "Plaquettes" resemble stacks of dishes, [[Screw thread|threads]], or beehives.<ref name="jedwab67">{{ cite journal |last1=Jedwab |first1=J. |title=La Magnetite en Plaquettes des Meteorites carbonees D'Alais, Ivuna et Orgueil |date=1967 |journal=Earth Planet. Sci. Lett. |volume=2 |pages=440-444}}</ref><ref name="j70" /><ref name="hb98" /> They are characteristic of CIs, and not found in CMs.<ref name="bp92" />
 Magnetite originated from continuing oxidation of sulfides: nominally [[troilite]] (stoichiometric FeS) but de facto [[pyrrhotite]] (Fe<sub>(1-x)</sub>S) with [[pentlandite]], [[pyrite]], and their [[Meteoritic iron|nickel substitutions]], etc.<ref>{{cite journal |last1=Larson E .E. |last2=Watson D. E. |last3=Herndon J. M. |last4=Rowe M. W. |title=Thermomagnetic analysis of meteorites, 1. C1 chondrites |date=1974 |journal=EPSL |volume=21 |pages=345-50 |quote="presumably FeS" }}</ref><ref>{{cite journal |last1=Watson D. E. |last2=Larson E. E. |last3=Herndon J. M. |last4=Rowe M. W. |title=Thermomag anal of meteorites, 2. C2 chondrites |date=1975 |journal=Earth Planet. Sci. Lett. |volume=27 |pages=101-07 }}</ref><ref name="hr83">{{cite journal |last1=Hyman M. |last2=Rowe M. W. |title=Magnetite in CI chondrites |date=1983 |journal=Proc. LSC 13 Part 2 |journal=J. Geo. Res. Suppl |volume=88 |pages=A736-40 }}</ref>This oxidation appears to have occurred in multiple generations.<ref name="hr83" /><ref name="tom150" />
@@ Line 155: / Line 162: @@
 === Physical parameters ===
 Because of their high porosity, CI chondrites have only a [[density]] of 2.2 g/cm<sup>3</sup>.
+==Natural History==
+=== Formation ===
+CI chondrites and the closely related CM chondrites are very rich in volatile substances, especially in water. It is assumed that they originally formed in the outer [[asteroid belt]], at a distance surpassing 4 [[Astronomical unit|AU]] – the reason for this being the so-called [[snow line]] situated at this distance and representing a temperature of 160&nbsp;[[Kelvin|K]]. At these conditions any water present condensed to ice and was therefore preserved. This is supported by the similarity of CI chondrites with the icy moons of the outer Solar system. Furthermore, there seems to exist a connection to [[comet]]s: like the comets, CI chondrites [[accretion (astrophysics)|accreted]] silicates, ice and other volatiles, as well as organic compounds (example: [[Comet Halley]]).
+===Occurrence===
+====Micrometeorites/Dust====
+====Ceres====
+====Comets?====
+==Antarctic CI chondrites (?)==
+Antarctica has been a fertile source of meteorites. Greater yields from the continent's ice fields have resulted in arguably CI or CI-like specimens, starting with Yamato 82042 and 82162 (Y 82042, Y82162). In 1992, Ikeda proposed that these meteorites, differing somewhat from non-Antarctic examples, should receive their own grouplet-<ref>{{cite journal |last1=Ikeda |first1=Y. |title=An overview of the research consortium, "Antarctic carbonaceous chondrites with CI affinities, Yamato-86720, Yamato-82162, and Belgica-7904" |journal=Proceedings, NIPR Symp. Antarctic Meteorites |date=1992 |volume=5 |pages=49–73}}</ref> at the time, there were, three, short of the five (unpaired) meteorites needed for a full group.<ref>{{cite book |last1=Wasson |first1=J. T. |title=Meteorites: Classification and Properties |date=1974 |publisher=Springer |isbn=978-3-642-65865-5}}</ref><ref>{{cite book |last1=Weisberg |first1=M. K. |title=Systematics and Evaluation of Meteorite Classification |date=2006 |publisher=University of Arizona Press |location=Tucson |isbn=9780816525621 |page=19}}</ref><ref>{{cite book |last1=Hutchison |first1=R. |title=Meteorites: A Petrologic, Chemical, and Isotopic Synthesis |date=2004 |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-47010-2}}</ref> These meteorites have measurably higher sulfide content, and an <sup>18</sup>O level even higher than the prior CI specimens, making them the heaviest in oxygen of all meteorites found.
+By 2015, the specimen list had grown: arguably Y 86029, 86720, 86789, 980115, Belgica 7904 and a desert chondrite, Dhofar 1988. King et al. renewed the call for a separate group, the "CY" chondrites.<ref>{{cite journal |last1=King |first1=A. J. |title=Modal Mineralogy of CI and CI-Like Chondrites by X-ray Diffraction |journal=Geochimica et Cosmochimica Acta |date=2015 |volume=165 |pages=148–60}}</ref><ref>{{cite journal |last1=King |first1=A. J. |title=Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy |journal=Earth, Planets and Space |date=2015 |volume=67 |page=198}}</ref>
 == Misclassification==
@@ Line 192: / Line 218: @@
 CI chondrites also have a high carbon content. Besides inorganic carbon compounds like graphite, diamond and carbonates, organic carbon compounds are represented. For instance, amino acids have been detected. This is a very important fact in the ongoing search for the [[origin of life]].
-== Formation ==
-CI chondrites and the closely related CM chondrites are very rich in volatile substances, especially in water. It is assumed that they originally formed in the outer [[asteroid belt]], at a distance surpassing 4 [[Astronomical unit|AU]] – the reason for this being the so-called [[snow line]] situated at this distance and representing a temperature of 160&nbsp;[[Kelvin|K]]. At these conditions any water present condensed to ice and was therefore preserved. This is supported by the similarity of CI chondrites with the icy moons of the outer Solar system. Furthermore, there seems to exist a connection to [[comet]]s: like the comets, CI chondrites [[accretion (astrophysics)|accreted]] silicates, ice and other volatiles, as well as organic compounds (example: [[Comet Halley]]).
-==Antarctic CI chondrites (?)==
-Antarctica has been a fertile source of meteorites. Greater yields from the continent's ice fields have resulted in arguably CI or CI-like specimens, starting with Yamato 82042 and 82162 (Y 82042, Y82162). In 1992, Ikeda proposed that these meteorites, differing somewhat from non-Antarctic examples, should receive their own grouplet-<ref>{{cite journal |last1=Ikeda |first1=Y. |title=An overview of the research consortium, "Antarctic carbonaceous chondrites with CI affinities, Yamato-86720, Yamato-82162, and Belgica-7904" |journal=Proceedings, NIPR Symp. Antarctic Meteorites |date=1992 |volume=5 |pages=49–73}}</ref> at the time, there were, three, short of the five (unpaired) meteorites needed for a full group.<ref>{{cite book |last1=Wasson |first1=J. T. |title=Meteorites: Classification and Properties |date=1974 |publisher=Springer |isbn=978-3-642-65865-5}}</ref><ref>{{cite book |last1=Weisberg |first1=M. K. |title=Systematics and Evaluation of Meteorite Classification |date=2006 |publisher=University of Arizona Press |location=Tucson |isbn=9780816525621 |page=19}}</ref><ref>{{cite book |last1=Hutchison |first1=R. |title=Meteorites: A Petrologic, Chemical, and Isotopic Synthesis |date=2004 |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-47010-2}}</ref> These meteorites have measurably higher sulfide content, and an <sup>18</sup>O level even higher than the prior CI specimens, making them the heaviest in oxygen of all meteorites found.
-By 2015, the specimen list had grown: arguably Y 86029, 86720, 86789, 980115, Belgica 7904 and a desert chondrite, Dhofar 1988. King et al. renewed the call for a separate group, the "CY" chondrites.<ref>{{cite journal |last1=King |first1=A. J. |title=Modal Mineralogy of CI and CI-Like Chondrites by X-ray Diffraction |journal=Geochimica et Cosmochimica Acta |date=2015 |volume=165 |pages=148–60}}</ref><ref>{{cite journal |last1=King |first1=A. J. |title=Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy |journal=Earth, Planets and Space |date=2015 |volume=67 |page=198}}</ref>
 ==See also==