Amino acids in Antarctic CM1 meteorites and their relationship to other carbonaceous chondrites

Abstract— CM2 carbonaceous chondrites are the most primitive material present in the solar system, and some of their subtypes, the CM and CI chondrites, contain up to 2 wt% of organic carbon. The CM2 carbonaceous chondrites contain a wide variety of complex amino acids, while the CI1 meteorites Orgueil and Ivuna display a much simpler composition, with only glycine and β‐alanine present in significant abundances. CM1 carbonaceous chondrites show a higher degree of aqueous alteration than CM2 types and therefore provide an important link between the CM2 and CI1 carbonaceous chondrites. Relative amino acid concentrations have been shown to be indicative for parent body processes with respect to the formation of this class of compounds. In order to understand the relationship of the amino acid composition between these three types of meteorites, we have analyzed for the first time three Antarctic CM1 chondrites, Meteorite Hills (MET) 01070, Allan Hills (ALH) 88045, and LaPaz Icefield (LAP) 02277, using gas chromatography‐mass spectrometry (GC‐MS) and high performance liquid chromatography‐fluorescence detection (HPLC‐FD). The concentrations of the eight most abundant amino acids in these meteorites were compared to those of the CM2s Murchison, Murray, Mighei, Lewis Cliff (LEW) 90500, ALH 83100, as well as the CI1s Orgueil and Ivuna. The total amino acid concentration in CM1 carbonaceous chondrites was found to be much lower than the average of the CM2s. Relative amino acid abundances were compared in order to identify synthetic relationships between the amino acid compositions in these meteorite classes. Our data support the hypothesis that amino acids in CM‐ and CI‐type meteorites were synthesized under different physical and chemical conditions and may best be explained with differences in the abundances of precursor compounds in the source regions of their parent bodies in combination with the decomposition of amino acids during extended aqueous alteration.     

Amino acid analyses of Antarctic CM2 meteorites using liquid chromatography‐time of flight‐mass spectrometry

Abstract— Amino acid analyses of the Antarctic CM2 chondrites Allan Hills (ALH) 83100 and Lewis Cliff (LEW) 90500 using liquid chromatography‐time of flight‐mass spectrometry (LC‐ToF‐MS) coupled with UV fluorescence detection revealed that these carbonaceous meteorites contain a suite of indigenous amino acids not present in Antarctic ice. Several amino acids were detected in ALH 83100, including glycine, alanine, β‐alanine, γ‐amino‐n‐butyric acid (γ‐ABA), and α‐aminoisobutyric acid (AIB) with concentrations ranging from 250 to 340 parts per billion (ppb). In contrast to ALH 83100, the CM2 meteorites LEW 90500 and Murchison had a much higher total abundance of these amino acids (440–3200 ppb). In addition, ALH 83100 was found to have lower abundances of the α‐dialkyl amino acids AIB and isovaline than LEW 90500 and Murchison. There are three possible explanations for the depleted amino acid content in ALH 83100: 1) amino acid leaching from ALH 83100 during exposure to Antarctic ice meltwater, 2) a higher degree of aqueous alteration on the ALH 83100 parent body, or 3) ALH 83100 originated on a chemically distinct parent body from the other two CM2 meteorites. The high relative abundance of ?‐amino‐n‐caproic acid (EACA) in the ALH 83100 meteorite as well as the Antarctic ice indicates that Nylon‐6 contamination from the Antarctic sample storage bags may have occurred during collection.     

Extraterrestrial organic compounds and cyanide in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison

Evaluating the water‐soluble organic composition of carbonaceous chondrites is key to understanding the inventory of organic matter present at the origins of the solar system and the subsequent processes that took place inside asteroid parent bodies. Here, we present a side‐by‐side analysis and comparison of the abundance and molecular distribution of aliphatic amines, aldehydes, ketones, mono‐ and dicarboxylic acids, and free and acid‐releasable cyanide species in the CM2 chondrites Aguas Zarcas and Murchison. The Aguas Zarcas meteorite is a recent fall that occurred in central Costa Rica and constitutes the largest recovered mass of a CM‐type meteorite after Murchison. The overall content of organic species we investigated was systematically higher in Murchison than in Aguas Zarcas. Similar to previous meteoritic organic studies, carboxylic acids were one to two orders of magnitude more abundant than other soluble organic compound classes investigated in both meteorite samples. We did not identify free cyanide in Aguas Zarcas and Murchison; however, cyanide species analyzed after acid digestion of the water‐extracted meteorite mineral matrix were detected and quantified at slightly higher abundances in Aguas Zarcas compared to Murchison. Although there were differences in the total abundances of specific compound classes, these two carbonaceous chondrites showed similar isomeric distributions of aliphatic amines and carboxylic acids, with common traits such as a complete suite of structural isomers that decreases in concentration with increasing molecular weight. These observations agree with their petrologic CM type‐2 classification, suggesting that these meteorites experienced similar organic formation processes and/or conditions during parent body aqueous alteration.     

A propensity for n‐ω‐amino acids in thermally altered Antarctic meteorites

Abstract– Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts‐per‐billion (ppb), generally much less abundant than in amino acid‐rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low‐temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Strecker–cyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straight‐chain, amine terminal (n‐ω‐amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n‐ω‐amino acids measured in one of the CV chondrites (δ¹³C approximately ?25‰) are consistent with ¹³C‐depletions observed previously in hydrocarbons produced by Fischer‐Tropsch type reactions. The predominance of n‐ω‐amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.     

The Distribution and Significance of Evaporitic Weathering Products on Antarctic Meteorites

Abstract— The distribution of white evaporitic deposits differs among different meteorite compositional groups and weathering categories of Antarctic meteorites. Evaporites occur with unusual frequency on carbonaceous chondrites, and are especially common in carbonaceous chondrites of weathering categories A and B. Among achondrites, weathering categories A and A/B show the most examples of evaporite weathering. Unlike carbonaceous chondrites and achondrites, most evaporite-bearing ordinary (H and L) chondrites are from rustier meteorites of weathering categories B and, to a lesser degree, B/C and C. LL chondrites are conspicuous by their complete lack of any evaporitic weathering product. Almost two-thirds of all evaporite-bearing meteorites belong to weathering categories A, A/B, and B. Where chemical data are available, surficial evaporite deposits are associated with elemental anomalies in meteorite interiors. Meteorites of weathering classes B, A/B, and even A may have experienced significant element redistribution and/or contamination as a result of terrestrial exposure. Evaporite formation during terrestrial weathering cannot be neglected in geochemical, cosmochemical, and mineralogical studies of Antarctic meteorites. A lower-case “e” should be added to the weathering classification of evaporite-bearing Antarctic meteorites, to inform meteorite scientists of the presence of evaporite deposits and their associated compositional effects.     

Distribution of aliphatic amines in CO,CV, and CK carbonaceous chondrites and relation to mineralogy and processing history

The analysis of water‐soluble organic compounds in meteorites provides valuable insights into the prebiotic synthesis of organic matter and the processes that occurred during the formation of the solar system. We investigated the concentration of aliphatic monoamines present in hot acid water extracts of the unaltered Antarctic carbonaceous chondrites, Dominion Range (DOM) 08006 (CO3) and Miller Range (MIL) 05013 (CO3), and the thermally altered meteorites, Allende (CV3), LAP 02206 (CV3), GRA 06101 (CV3), Allan Hills (ALH) 85002 (CK4), and EET 92002 (CK5). We have also reviewed and assessed the petrologic characteristics of the meteorites studied here to evaluate the effects of asteroidal processing on the abundance and molecular distributions of monoamines. The CO3, CV3, CK4, and CK5 meteorites studied here contain total concentrations of amines ranging from 1.2 to 4.0 nmol g^?1 of meteorite; these amounts are 1–3 orders of magnitude below those observed in carbonaceous chondrites from the CI, CM, and CR groups. The low‐amine abundances for CV and CK chondrites may be related to their extensive degree of thermal metamorphism and/or to their low original amine content. Although the CO3 meteorites, DOM 08006 and MIL 05013, do not show signs of thermal and aqueous alteration, their monoamine contents are comparable to those observed in moderately/extensively thermally altered CV3, CK4, and CK5 carbonaceous chondrites. The low content of monoamines in pristine CO carbonaceous chondrites suggests that the initial amounts, and not asteroidal processes, play a dominant role in the content of monoamines in carbonaceous chondrites. The primary monoamines, methylamine, ethylamine, and n‐propylamine constitute the most abundant amines in the CO3, CV3, CK4, and CK5 meteorites studied here. Contrary to the predominance of n‐ω‐amino acid isomers in CO3 and thermally altered meteorites, there appears to be no preference for the larger n‐amines.     

The effects of parent body processes on amino acids in carbonaceous chondrites

Abstract– To investigate the effect of parent body processes on the abundance, distribution, and enantiomeric composition of amino acids in carbonaceous chondrites, the water extracts from nine different powdered CI, CM, and CR carbonaceous chondrites were analyzed for amino acids by ultra performance liquid chromatography‐fluorescence detection and time‐of‐flight mass spectrometry (UPLC‐FD/ToF‐MS). Four aqueously altered type 1 carbonaceous chondrites including Orgueil (CI1), Meteorite Hills (MET) 01070 (CM1), Scott Glacier (SCO) 06043 (CM1), and Grosvenor Mountains (GRO) 95577 (CR1) were analyzed using this technique for the first time. Analyses of these meteorites revealed low levels of two‐ to five‐carbon acyclic amino alkanoic acids with concentrations ranging from approximately 1 to 2,700 parts‐per‐billion (ppb). The type 1 carbonaceous chondrites have a distinct distribution of the five‐carbon (C₅) amino acids with much higher relative abundances of the γ‐ and δ‐amino acids compared to the type 2 and type 3 carbonaceous chondrites, which are dominated by α‐amino acids. Much higher amino acid abundances were found in the CM2 chondrites Murchison, Lonewolf Nunataks (LON) 94102, and Lewis Cliffs (LEW) 90500, the CR2 Elephant Moraine (EET) 92042, and the CR3 Queen Alexandra Range (QUE) 99177. For example, α‐aminoisobutyric acid (α‐AIB) and isovaline were approximately 100 to 1000 times more abundant in the type 2 and 3 chondrites compared to the more aqueously altered type 1 chondrites. Most of the chiral amino acids identified in these meteorites were racemic, indicating an extraterrestrial abiotic origin. However, nonracemic isovaline was observed in the aqueously altered carbonaceous chondrites Murchison, Orgueil, SCO 06043, and GRO 95577 with l ‐isovaline excesses ranging from approximately 11 to 19%, whereas the most pristine, unaltered carbonaceous chondrites analyzed in this study had no detectable l ‐isovaline excesses. These results are consistent with the theory that aqueous alteration played an important role in amplification of small initial left handed isovaline excesses on the parent bodies.     

A chemical sequence of macromolecular organic matter in the CM chondrites

Abstract— A new organic parameter is proposed to show a chemical sequence of organic matter in carbonaceous chondrites, using carbon, hydrogen, and nitrogen concentrations of solvent‐insoluble and high‐molecular weight organic matter (macromolecules) and the molecular abundance of solvent‐extractable organic compounds. The H/C atomic ratio of the macromolecule purified from nine CM chondrites including the Murchison, Sayama, and seven Antarctic meteorites varies widely from 0.11 to 0.72. During the H/C change of ?0.7 to ?0.3, the N/C atomic ratio remains at ?0.04, followed by a sharp decline from ?0.040 to ?0.017 between H/C ratios from ?0.3 to ?0.1. The H/CN/C sequence shows different degrees of organic matter thermal alteration among these chondrites in which the smaller H/C‐N/C value implies higher alteration levels on the meteorite parent body. In addition, solvent‐extractable organic compounds such as amino acids, carboxylic acids, and polycyclic aromatic hydrocarbons are abundant only in chondrites with macromolecular H/C values >?0.5. These organic compounds were extremely depleted in the chondrites with a macromolecular H/C value of <?0.5. Possibly, most solvent‐extractable organic compounds could have been lost during the thermal alteration event that caused the H/C ratio of the macromolecule to fall below 0.4.     

Amino acids in the Tagish Lake meteorite

Abstract— High‐performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and CI carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the CI Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated from a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P‐ or D‐type asteroids. If the Tagish Lake meteorite was indeed derived from these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.     

The amino acid and polycyclic aromatic hydrocarbon compositions of the promptly recovered CM2 Winchcombe carbonaceous chondrite

The rapid recovery of the Winchcombe meteorite offers a valuable opportunity to study the soluble organic matter (SOM) profile in pristine carbonaceous astromaterials. Our interests in the biologically relevant molecules, amino acids—monomers of protein, and the most prevalent meteoritic organics—polycyclic aromatic hydrocarbons (PAHs) are addressed by analyzing the solvent extracts of a Winchcombe meteorite stone using gas chromatography mass spectrometry. The Winchcombe sample contains an amino acid abundance of ~1132 parts-per-billion that is about 10 times lower than other CM2 meteorites. The detection of terrestrially rare amino acids, including α-aminoisobutyric acid (AIB); isovaline; β-alanine; α-, β-, and γ-amino-n-butyric acids; and 5-aminopentanoic acid, and the racemic enantiomeric ratios (D/L = 1) observed for alanine and isovaline indicate that these amino acids are indigenous to the meteorite and not terrestrial contaminants. The presence of predominantly α-AIB and isovaline is consistent with their formation via the Strecker-cyanohydrin synthetic pathway. The L-enantiomeric excesses in isovaline previously observed for aqueously altered meteorites were viewed as an indicator of parent body aqueous processing; thus, the racemic ratio of isovaline observed for Winchcombe, alongside the overall high free:total amino acid ratio, and the low amino acid concentration suggest that the analyzed stone is derived from a lithology that has experienced brief episode(s) of aqueous alteration. Winchcombe also contains 2- to 6-ring alkylated and nonalkylated PAHs. The low total PAHs abundance (6177 ppb) and high nonalkylated:alkylated ratio are distinct from that observed for heavily aqueously altered CMs. The weak petrographic properties of Winchcombe, as well as the discrepancies observed for the Winchcombe SOM content—a low total amino acid abundance comparable to heavily altered CMs, and yet the high free:total amino acid and nonalkylated:alkylated PAH ratios are on par with the less altered CMs—suggest that Winchcombe could represent a class of weak, poorly lithified meteorite not been previously studied.     

Effect of polychromatic X‐ray microtomography imaging on the amino acid content of the Murchison CM chondrite

X‐ray microcomputed tomography (μCT) is a useful means of characterizing cosmochemical samples such as meteorites or robotically returned samples. However, there are occasional concerns that the use of μCT may be detrimental to the organic components of a chondrite. Small organic compounds such as amino acids comprise up to ~10% of the total solvent extractable carbon in CM carbonaceous chondrites. We irradiated three samples of the Murchison CM carbonaceous chondrite under conditions akin to and harsher than those typically used during typical benchtop X‐ray μCT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed Murchison control sample occurred. After subjecting three meteorite samples to ionizing radiation dosages between ~300 Gray (Gy) and 3 kGy with bremstrahlung X‐rays, we analyzed the amino acid content of each sample. Within sampling and analytical errors, we cannot discern differences in the amino acid abundances and amino acid enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We conclude that a polychromatic X‐ray μCT experiment does not alter the abundances of amino acids to a degree greater than how well those abundances are measured with our techniques and therefore any damage to amino acids is minimal.     

The evolution of polycyclic aromatic hydrocarbons under simulated inner asteroid conditions

Large polycyclic aromatic hydrocarbons (PAHs) are an important component of the interstellar medium. PAHs have been identified in the soluble and insoluble matter of carbonaceous chondrites (CCs). Here, we study the evolution of PAHs under conditions relevant to the interiors of asteroids and compare our results to PAHs observed in CCs. We have performed long‐term and short‐term hydrothermal experiments, in which we exposed PAH‐mineral mixture analogs of meteorites to temperature conditions representative of those predicted for asteroids interiors. Our results show that small PAHs with melting points within the aqueous alteration temperature of CCs form carbonaceous spherules in the presence of water. In this work, we describe the microstructure and morphology of these spherules. We discuss the similarities and differences compared to globules isolated from CCs.     

Indigenous amino acids in primitive CR meteorites

Abstract— –CR chondrites are among the most primitive meteorites. In this paper, we report the first measurements of amino acids in Antarctic CR meteorites. Three CRs, Elephant Moraine (EET) 92042, Graves Nunataks (GRA) 95229, and Grosvenor Mountains (GRO) 95577, were analyzed for their amino acid content using high‐performance liquid chromatography with UV fluorescence detection (HPLC‐FD) and gas chromatography–mass spectrometry (GC‐MS). Our data show that EET 92042 and GRA 95229 are the most amino acid–rich chondrites ever analyzed, with total amino acid concentrations ranging from 180 ppm to 249 ppm. The most abundant amino acids present in the EET 92042 and GRA 95229 meteorites are the α‐amino acids glycine, isovaline, α‐aminoisobutyric acid (α‐AIB), and alanine, with δ¹³C values ranging from +31.6‰ to +50.5‰. The carbon isotope results together with racemic enantiomeric ratios determined for most amino acids strongly indicate an extraterrestrial origin for these compounds. Compared to Elephant Moraine (EET) 92042 and GRA 95229, the more aqueously altered GRO 95577 is depleted in amino acids. In both CRs and CMs, the absolute amino acid abundances appear to be related to the degree of aqueous alteration in their parent bodies. In addition, the relative abundances of α‐AIB and β‐alanine in the Antarctic CRs also appear to depend on the degree of aqueous alteration.     

The preservation state of organic matter in meteorites from Antarctica

Abstract— The recovery of large numbers of meteorites from Antarctica has dramatically increased the amount of extraterrestrial material available for laboratory studies of solar system origin and evolution. Yet, the great age of Antarctic meteorites raises the concern that significant amounts of terrestrial weathering has corrupted their pre‐terrestrial record. Organic matter found in carbonaceous chondrites is one of the components most susceptible to alteration by terrestrial processes. To assess the effects of Antarctic weathering on both non‐Antarctic and Antarctic chondritic organic matter, a number of CM chondrites have been analyzed. Mössbauer spectroscopy has been used to ascertain pre‐terrestrial and terrestrial oxidation levels, while pyrolysis‐gas chromatography‐mass spectrometry was used to determine the constitution of any organic matter present. Increased oxidation levels for iron bearing minerals within the non‐Antarctic chondrites are likely to be a response to increased amounts of parent body aqueous alteration. Parent body processing also appears to remove ether bonds from organic material and alkyl side chains from its constituent units. The iron in Antarctic chondrites is generally more oxidized than that in their non‐Antarctic counterparts, reflecting terrestrial weathering. Antarctic weathering of chondritic organic matter appears to proceed in a similar way to parent body aqueous alteration and simply enhances the organic responses observed in the non‐Antarctic data set. Degradation of the record of preterrestrial processes in Antarctic chondrites should be taken into account when interpreting data from these meteorites.     

Molecular distribution, 13C‐isotope,and enantiomeric compositions of carbonaceous chondrite monocarboxylic acids

The water‐soluble organic compounds in carbonaceous chondrite meteorites constitute a record of the synthetic reactions occurring at the birth of the solar system and those taking place during parent body alteration and may have been important for the later origins and development of life on Earth. In this present work, we have developed a novel methodology for the simultaneous analysis of the molecular distribution, compound‐specific δ¹³C, and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot‐water extracts of 16 carbonaceous chondrites from CM, CR, CO, CV, and CK groups. We observed high concentrations of meteoritic MCAs, with total carbon weight percentages which in some cases approached those of carbonates and insoluble organic matter. Moreover, we found that the concentration of MCAs in CR chondrites is higher than in the other meteorite groups, with acetic acid exhibiting the highest concentration in all samples. The abundance of MCAs decreased with increasing molecular weight and with increasing aqueous and/or thermal alteration experienced by the meteorite sample. The δ¹³C isotopic values of MCAs ranged from ?52 to +27‰, and aside from an inverse relationship between δ¹³C value and carbon straight‐chain length for C₃–C₆ MCAs in Murchison, the ¹³C‐isotopic values did not correlate with the number of carbon atoms per molecule. We also observed racemic compositions of 2‐methylbutanoic acid in CM and CR chondrites. We used this novel analytical protocol and collective data to shed new light on the prebiotic origins of chondritic MCAs.     

The Aguas Zarcas (CM2) meteorite: New insights into early solar system organic chemistry

To date, the CM2 class of carbonaceous chondrites has provided the most detailed view of organic synthesis in the early solar system. Organic‐rich chondrites actually observed falling to Earth (“Falls”), for example, the Murchison meteorite in 1969, are even more rare. The April 23, 2019 fall of the Aguas Zarcas meteorite is therefore the most significant CM2 fall since Murchison. Samples collected immediately following the fall provide the rare opportunity to analyze its bulk mineralogy and organic inventory relatively free of terrestrial contamination. According to the Meteoritical Bulletin, Aguas Zarcas (“AZ” or “Zarcas”) is dominated by serpentine, similar to other CM2 chondrites. Likewise, our initial analyses of AZ were meant to give a broad view of its soluble organic inventory relative to other carbonaceous chondrites. We observe that while it is rich in hydrocarbons, carboxylic acids, dicarboxylic acids, sugar alcohols, and sugar acids, some of these classes may be of lesser abundance than in the more well known carbonaceous chondrites such as Murchison. Compared generally with other CM2 meteorites, the most significant finding is the absence, or relatively low levels, of three otherwise common constituents: ammonia, amino, acids, and amines. Overall, this meteorite adds to the building database of prebiotic compounds available to the ancient Earth.     

The amino acid and hydrocarbon contents of the Paris meteorite: Insights into the most primitive CM chondrite

The Paris meteorite is one of the most primitive carbonaceous chondrites. It is reported to be the least aqueously altered CM chondrite, and to have experienced only weak thermal metamorphism. We have analyzed for the first time the amino acid and hydrocarbon contents of this pristine meteorite by gas chromatography–mass spectrometry (GC–MS). When plotting the relative amino acids abundances of several CM chondrites according to the increasing hydrothermal scale (petrologic subtypes), from the CM2.7/2.8 Paris to the CM2.0 MET 01070, Paris has the lowest relative abundance of β‐alanine/glycine (0.15), which fits with the relative abundances of β‐alanine/glycine increasing with increasing aqueous alteration for CM chondrites. These results confirm the influence of aqueous alteration on the amino acid abundances and distribution. The amino acid analysis shows that the isovaline detected in this meteorite is racemic (d /l  = 0.99 ± 0.08; l ‐enantiomer excess = 0.35 ± 0.5%; corrected d /l  = 1.03; corrected l ‐enantiomer excess = ?1.4 ± 2.6%). The identified hydrocarbons show that Paris has n‐alkanes ranging from C₁₆ to C₂₅ and 3‐ to 5‐ring nonalkylated polycyclic aromatic hydrocarbons (PAHs). The lack of alkylated PAHs in Paris seems to be also related to this low degree of aqueous alteration on its parent body. The extraterrestrial hydrocarbon content, suggested by the absence of any biomarker, may well have a presolar origin. The chemistry of the Paris meteorite may thus be closely related to the early stages of the solar nebula with a contribution from interstellar (molecular cloud) precursors.     

Extraterrestrial amino acids and L‐enantiomeric excesses in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison

The abundances, distributions, enantiomeric ratios, and carbon isotopic compositions of amino acids in two fragments of the Aguas Zarcas CM2 type carbonaceous chondrite fall and a fragment of the CM2 Murchison meteorite were determined via liquid chromatography time‐of‐flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. A suite of two‐ to six‐carbon aliphatic primary amino acids was identified in the Aguas Zarcas and Murchison meteorites with abundances ranging from ~0.1 to 158 nmol/g. The high relative abundances of α‐amino acids found in these meteorites are consistent with a Strecker‐cyanohydrin synthesis on these meteorite parent bodies. Amino acid enantiomeric and carbon isotopic measurements in both fragments of the Aguas Zarcas meteorites indicate that both samples experienced some terrestrial protein amino acid contamination after their fall to Earth. In contrast, similar measurements of alanine in Murchison revealed that this common protein amino acid was both racemic (D ≈ L) and heavily enriched in ¹³C, indicating no measurable terrestrial alanine contamination of this meteorite. Carbon isotope measurements of two rare non‐proteinogenic amino acids in the Aguas Zarcas and Murchison meteorites, α‐aminoisobutyric acid and D‐ and L‐isovaline, also fall well outside the typical terrestrial range, confirming they are extraterrestrial in origin. The detections of non‐terrestrial L‐isovaline excesses of ~10–15% in both the Aguas Zarcas and Murchison meteorites, and non‐terrestrial L‐glutamic acid excesses in Murchison of ~16–40% are consistent with preferential enrichment of circularly polarized light generated L‐amino acid excesses of conglomerate enantiopure crystals during parent body aqueous alteration and provide evidence of an early solar system formation bias toward L‐amino acids prior to the origin of life.     

Chemical analyses of meteorites at the Smithsonian Institution: An update

Abstract— Thirteen new meteorites and three meteorite inclusions have been analyzed. Their results have been incorporated into earlier published data for a comprehensive reference to all analyzed meteorites at the Smithsonian Institution. The six tables facilitate a convenient overlook of meteorite data. Table 1 presents an alphabetical list of analyzed meteorites, Table 2 chemical analyses of stony meteorites, Table 3 chemical analyses of iron meteorites, Table 4 elemental composition of stony meteorites, Table 5 average composition of carbonaceous chondrites and achondrites (falls and finds), and Table 6 presents average composition of H, L, LL, and Antarctic chondrites (falls and finds). The tables are available online at the journal's Web site http:meteoritics.org .     

Evaporite formation during weathering of Antarctic meteorites––A weathering census analysis based on the ANSMET database

Abstract– Weathering of meteorites at the scale of the entire Antarctic Search for Meteorites program population is studied by analyzing the recent version of the online Antarctic meteorite classification database that includes information about 15,263 meteorites. This paper updates, supplements, and expands on the last Antarctic meteorite weathering census by Velbel (1988 , Meteoritics 23:151–159). On average 5% of all Antarctic meteorites are indicated as evaporite bearing in the Antarctic Meteorite Database. Evaporite formation depends on compositional group. Evaporites are much more common on C chondrites than on ordinary chondrites, supporting previous findings. Ordinary chondrites of petrologic type 3 more often have evaporites on their surface than meteorites of other petrologic types. Contrary to previous findings, there is no apparent relation between evaporite formation and meteorite rustiness. Some meteorite‐bearing fields influence the frequency of evaporite‐mineral formation on meteorites. The influence of location is apparently related to differences in environmental conditions, most probably microclimate or/and hydrologic conditions. There is no relation between abundance of evaporite‐bearing meteorites and distance from the sea. Evaporite formation varies with year of collection; however, it was not possible to distinguish whether this is related to annual changes in environment or an artifact of sample categorization or curation.