New Insights into the Heterogeneity of the Tagish Lake Meteorite: Soluble Organic Compositions of Variously Altered Specimens

The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compoundspecific 13C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organicdepleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organicdepleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds

The Sariçiçek Howardite Fall in Turkey: Source Crater of HED Meteorites on Vesta and İmpact Risk of Vestoids

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 ± 17 Ma, K-Ar age of ~3.9 Ga, and the U,Th-He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic, geochemical and O-, Cr- and Tiisotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 kms-1 from NW, fragmentations at 37, 33, 31 and 27 km altitude, and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antonia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed ~22 Ma ago

Aliphatic Amines in Antarctic CR2, CM2, and CM1/2 Carbonaceous Chondrites

Meteoritic water-soluble organic compounds provide a unique record of the processes that occurred during the formation of the solar system and the chemistry preceding the origins of life on Earth. We have investigated the molecular distribution, compound-specific delta13C isotopic ratios and enantiomeric compositions of aliphatic monoamines present in the hot acid-water extracts of the carbonaceous chondrites LAP 02342 (CR2), GRA 95229 (CR2), LON 94101 (CM2), LEW 90500 (CM2), and ALH 83100 (CM1/2). Analyses of the concentration of monoamines in these meteorites revealed: (a) the CR2 chondrites studied here contain higher concentrations of monoamines relative to the analyzed CM2 chondrites; (b) the concentration of monoamines decreases with increasing carbon number; and (c) isopropylamine is the most abundant monoamine in these CR2 chondrites, while methylamine is the most abundant amine species in these CM2 and CM1/2 chondrites. The delta13C values of monoamines in CR2 chondrite do not correlate with the number of carbon atoms; however, in CM2 and CM1/2 chondrites, the 13C enrichment decreases with increasing monoamine carbon number. The delta13C values of methylamine in CR2 chondrites ranged from 1 to +10per mille, while in CM2 and CM1/2 chondrites the delta13C values of methylamine ranged from +41 to +59per mille. We also observed racemic compositions of sec-butylamine, 3-methyl-2-butylamine, and sec-pentylamine in the studied carbonaceous chondrites. Additionally, we compared the abundance and delta13C isotopic composition of monoamines to those of their structurally related amino acids. We found that monoamines are less abundant than amino acids in CR2 chondrites, with the opposite being true in CM2 and CM1/2 chondrites. We used these collective data to evaluate different primordial synthetic pathways for monoamines in carbonaceous chondrites and to understand the potential common origins these molecules may share with meteoritic amino acids

The Origin of Amino Acids in Lunar Regolith Samples

We analyzed the amino acid content of seven lunar regolith samples returned by the Apollo 16 and Apollo 17 missions and stored under NASA curation since collection using ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Consistent with results from initial analyses shortly after collection in the 1970s, we observed amino acids at low concentrations in all of the curated samples, ranging from 0.2 parts-per-billion (ppb) to 42.7 ppb in hot-water extracts and 14.5 ppb to 651.1 ppb in 6M HCl acid-vapor-hydrolyzed, hot-water extracts. Amino acids identified in the Apollo soil extracts include glycine, D- and L-alanine, D- and L-aspartic acid, D- and L-glutamic acid, D- and L-serine, L-threonine, and L-valine, all of which had previously been detected in lunar samples, as well as several compounds not previously identified in lunar regoliths: -aminoisobutyric acid (AIB), D-and L-amino-n-butyric acid (-ABA), DL-amino-n-butyric acid, -amino-n-butyric acid, -alanine, and -amino-n-caproic acid. We observed an excess of the L enantiomer in most of the detected proteinogenic amino acids, but racemic alanine and racemic -ABA were present in some samples

Effect of Polychromatic X-Ray Microtomography Imaging on the Amino Acid Content of the Murchison CM Chondrite

X-ray microcomputed tomography is a useful means of characterizing cosmochemical samples such as meteorites or robotically returned samples. However, there are occasional concerns that the use of CT 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 CT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a non-exposed 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 found no differences in the amino acid abundances and amino acid enantiomeric ratios when comparing the control samples (non-exposed Murchison) and the irradiated samples. We conclude that a polychromatic X-ray CT experiment has no detectable effect on the amino acid content of a CM type carbonaceous chondrite

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 similar to 0.1 to 158 nmol/g. The high relative abundances of alpha-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 approximate to L) and heavily enriched in C-13, 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, alpha-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 similar to 10-15% in both the Aguas Zarcas and Murchison meteorites, and non-terrestrial L-glutamic acid excesses in Murchison of similar to 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.NASA Astrobiology InstitutePublic domain articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

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.NASA’s Planetary Science Division Research Program12 month embargo; first published online 22 June 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Prokaryotic and Fungal Characterization of the Facilities Used to Assemble, Test, and Launch the OSIRIS-REx Spacecraft

To characterize the ATLO (Assembly, Test, and Launch Operations) environment of the OSIRIS-REx spacecraft, we analyzed 17 aluminum witness foils and two blanks for bacterial, archaeal, fungal, and arthropod DNA. Under NASA's Planetary Protection guidelines, OSIRIS-REx is a Category II outbound, Category V unrestricted sample return mission. As a result, it has no bioburden restrictions. However, the mission does have strict organic contamination requirements to achieve its primary objective of returning pristine carbonaceous asteroid regolith to Earth. Its target, near-Earth asteroid (101955) Bennu, is likely to contain organic compounds that are biologically available. Therefore, it is useful to understand what organisms were present during ATLO as part of the larger contamination knowledge effort-even though it is unlikely that any of the organisms will survive the multi-year deep space journey. Even though these samples of opportunity were not collected or preserved for DNA analysis, we successfully amplified bacterial and archaeal DNA (16S rRNA gene) from 16 of the 17 witness foils containing as few as 7 ± 3 cells per sample. Fungal DNA (ITS1) was detected in 12 of the 17 witness foils. Despite observing arthropods in some of the ATLO facilities, arthropod DNA (COI gene) was not detected. We observed 1,009 bacterial and archaeal sOTUs (sub-operational taxonomic units, 100% unique) and 167 fungal sOTUs across all of our samples (25-84 sOTUs per sample). The most abundant bacterial sOTU belonged to the genus Bacillus. This sOTU was present in blanks and may represent contamination during sample handling or storage. The sample collected from inside the fairing just prior to launch contained several unique bacterial and fungal sOTUs that describe previously uncharacterized potential for contamination during the final phase of ATLO. Additionally, fungal richness (number of sOTUs) negatively correlates with the number of carbon-bearing particles detected on samples. The total number of fungal sequences positively correlates with total amino acid concentration. These results demonstrate that it is possible to use samples of opportunity to characterize the microbiology of low-biomass environments while also revealing the limitations imposed by sample collection and preservation methods not specifically designed with biology in mind.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]