Abundant ammonia in primitive asteroids and the case for a possible exobiology

Pizzarello, Sandra; Williams, Lynda B.; Lehman, Jennifer; Holland, Gregory P.; Yarger, Jeffery L.

doi:10.1073/pnas.1014961108

Cited by 91 publications

(58 citation statements)

References 24 publications

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“…The presence of hydrogen cyanide and ammonia as synthetic precursor molecules has been deduced in hydrated carbonaceous chondrites based on the presence of α-amino acids, α-hydroxy acids, and iminodicarboxylic acids reported in the Murchison meteorite, which supports a Strecker-type synthesis requiring hydrogen cyanide and ammonia (13,(26)(27)(28)(29). Additionally, abundant ammonia has been detected in the CR2 carbonaceous chondrite GRA 95229 after hydrothermal treatment (30), which was one of the meteorites in our study.…”

Section: Resultsmentioning

confidence: 75%

“…Furthermore, there is an apparent correlation between purine diversity and the diversity of other small organic species, such as amino acids (5), with the maximum diversity found in CM2 carbonaceous chondrites. Interestingly, this correlation does not hold for the abundances of such compounds; for example, CR2 and CR3 meteorites are rich in amino acids and small amines (5,20,21) but poor in purines. Based on our measurements, the CM2 carbonaceous chondrites appear to have provided a more favorable environment for the formation and/or preservation of purines compared to other types of carbonaceous chondrites.…”

Section: Resultsmentioning

confidence: 99%

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Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

Callahan

Smith

Cleaves

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

514

415

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All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode genetic information. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of life on the early Earth; however, the origin and formation of nucleobases in meteorites has been debated for over 50 y. So far, the few nucleobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenous meteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formic acid extracts of 12 different meteorites by liquid chromatography-mass spectrometry. The Murchison and Lonewolf Nunataks 94102 meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs: purine, 2,6-diaminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analogs were not detected above our parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and an Antarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammonium cyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supports an extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventory available for constructing the first genetic molecules.

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Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

Callahan

Smith

Cleaves

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

514

415

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“…been short and icy, i.e., in early parent body, proto-planetesimal aggregates (26), or protoplanetary disc (27) environments, with the ammonia abundance that characterizes these type of stones providing a lower freezing point of water (8). Alternative formation pathways to α-amino acids besides Strecker-type syntheses might also allow molecular asymmetry but are not known or easy to propose based on current data.…”

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confidence: 97%

“…For example, highly altered GRO1 contains only one amine (methylamine), consistent with its amino acids depletion, but also displays a significant ammonia amount, while less aqueously altered LAP has the largest observed abundance of both ammonia and amines (3). Given that CR2 insoluble organic material (IOM) was shown to thermolytically release ammonia and traces of methylamine (8,33), these results could be reasonably explained by assuming that extended water phases had a similar effect on CR IOMs at lower T, increased free ammonia, and, possibly, preserved it on clays during their concomitant formation (vide infra). Results for CR alkyl compounds containing only oxygen (Tables S6-S9) can be best overviewed in Fig.…”

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confidence: 99%

“…Among CRs, GRA1 amino acids display δD values up to þ7;200‰ (2), the largest ever determined for an extraterrestrial molecule by direct analysis and falls within δD values established spectroscopically for molecules of the interstellar medium (þ5;800 to þ45;000) (7). Although available knowledge for the cosmic distribution of nitrogen isotopes is less detailed than for D/H or 13 C∕ 12 C ratios, δ 15 N values of þ77 to þ139‰ for GRA1 amino acids (3), þ137‰ for GRA1 ammonia (3), and þ223‰ for its insoluble organic material-bound ammonia (8) speak to a long cosmic lineage for these compounds as well (9,10).…”

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confidence: 99%

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Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution

Pizzarello

Monroe

Лауретта

2012

Proc. Natl. Acad. Sci. U.S.A.

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134

153

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Carbonaceous chondrites are meteoritic fragments of asteroids that avoided the geological reprocessing of larger planets and allow laboratory probing of early solar-nebula materials. Among these, Renazzo-type (CR) chondrites found in Antarctica appear remarkably pristine and are distinguished by abundant organic materials and water-soluble molecules such as amino acids and ammonia. We present a comprehensive analysis of the organic composition of selected CR meteorites of different petrographic classification and compare compounds' abundance and distribution as they may relate to asteroidal aqueous processing and concomitant evolution of the mineral phases. We found that several CR compounds such as amino acids and sugar alcohols are fully represented in stones with no or minimal water exposure indicating a formation that, if solar, preceded parent body processes. The most pristine CRs also revealed natal enantiomeric excesses (ee) of up to 60%, much larger than ever recorded. However, aqueous alteration appears to affect CR soluble organic composition and abundances, in particular some diastereomeric amino acids may gauge its extent by the consequent racemization of their ee.primitive asteroids | abiotic molecular evolution | solar ices | clays C R meteorites are characterized by several petrologic, geochemical, and isotopic features, such as containing large chondrules, high Fe-Ni metal abundances, and distinct wholerock O-isotopic distributions (1). However, only recent comprehensive analyses of the soluble and insoluble organic materials in two pristine* CR2 † meteorites, GRA 95229 (GRA1) and LAP 02342 (LAP) (2, 3) revealed what is possibly their most distinguishing characteristic vis-à-vis other carbonaceous chondrites (CC) types (i.e., soluble organic suites that are overall unique for having a preponderance of water-over solvent-soluble compounds). Ammonia is the most abundant single molecule detected in CR2 water extracts, and amino acids are their largest component, unlike, for example, in the Murchison meteorite where hydrocarbons are the dominant molecular species.Amino acids have been the most captivating findings in CC meteorites since the fall of Murchison (4) because several of the compounds have exact molecular correspondence with biomolecules and possible pre-biotic significance. In intervening studies, however, the detection of a diverse and apparently stochastic suite of compounds in many meteorites made it difficult to propose how this random mix could have found effective chemical pathways toward the origin of life (5). CR2s have significantly changed that perspective with their main compositional abundances of water-soluble and N-containing molecular species.CC materials relied on a long cosmic history for their formation, which spanned solar as well as presolar environments. In particular, the high D and 13 C isotopic enrichments of some CC organic compounds have revealed their lineage from cold cosmic regimes (6). Among CRs, GRA1 amino acids display δD values up to þ7;200‰ (2), the larges...

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Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

Suzuki

Furukawa

Kobayashi

et al. 2015

Geochem Geophys Geosyst

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The emergence of life's building blocks, such as amino acids and nucleobases, on the prebiotic Earth was a critical step for the beginning of life. Reduced species with low mass, such as ammonia, amines, or carboxylic acids, are potential precursors for these building blocks of life. These precursors may have been provided to the prebiotic ocean by carbonaceous chondrites and chemical reactions related to meteorite impacts on the early Earth. The impact of extraterrestrial objects on Earth occurred more frequently during this period than at present. Such impacts generated shock waves in the ocean, which have the potential to progress chemical reactions to form the building blocks of life from reduced species. To simulate shock-induced reactions in the prebiotic ocean, we conducted shock-recovery experiments on ammonium bicarbonate solution and ammonium formate solution at impact velocities ranging from 0.51 to 0.92 km/s. In the products from the ammonium formate solution, several amino acids (glycine, alanine, ß-alanine, and sarcosine) and aliphatic amines (methylamine, ethylamine, propylamine, and butylamine) were detected, although yields were less than 0.1 mol % of the formic acid reactant. From the ammonium bicarbonate solution, smaller amounts of glycine, methylamine, ethylamine, and propylamine were formed. The impact velocities used in this study represent minimum cases because natural meteorite impacts typically have higher velocities and longer durations. Our results therefore suggest that shock waves could have been involved in forming life's building blocks in the ocean of prebiotic Earth, and potentially in aquifers of other planets, satellites, and asteroids.

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Abundant ammonia in primitive asteroids and the case for a possible exobiology

Cited by 91 publications

References 24 publications

Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution

Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

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