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Jason P. Dworkin

Publications and source records attributed to Jason P. Dworkin.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Enantioselective Three-Dimensional High-Performance Liquid Chromatographic Determination of Amino Acids in the Hayabusa2 Returned Samples from the Asteroid Ryugu

The chirality of amino acids in extraterrestrial materials may provide an insight into the origin of the essential L-enantiopure amino acids in the terrestrial biosphere. In 2020, the Hayabusa2 mission succeeded in bringing back surface materials from the C-type asteroid (162173) Ryugu to the Earth. Amino acids were one of the targeted organic molecules to be studied in the Ryugu samples. To analyze the various structural isomers of amino acids, which were expected to be present, from the limited amount of the returned samples, the development of a highly-sensitive and selective analytical method was necessary. In the present study, a three-dimensional high-performance liquid chromatography (3D-HPLC) system has been developed for the enantioselective determination of five proteinogenic and three non-proteinogenic amino acids in the Ryugu samples, in which amino acids in the sample were separated by reversed-phase, anion-exchange and enantioselective columns after the fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiozole. The applicability of the analytical system to the extraterrestrial samples was evaluated by analyzing several types of carbonaceous meteorites before applying the system to the Ryugu samples. In the analysis of the Ryugu samples, all of the target amino acids were successfully determined quantitatively. Non-proteinogenic amino acids including 2-amino-n-butyric acid, isovaline and norvaline, rarely present in the terrestrial environment, were found as almost racemic mixtures with 47.1 to 55.2%L.

Amino acids↗
NASA NTRS2023

The Nature of Insoluble Organic Matter in Sutter’s Mill and Murchison Carbonaceous Chondrites: Testing the Effect of X-ray Computed Tomography (XCT) and Exploring Parent Body Organic Molecular Evolution

This study analyzed samples of the Murchison and Sutter’s Mill carbonaceous chondrite meteorites in support of the future analysis of samples returned from the asteroid (10155) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission. Focusing specifically on the insoluble organic matter (IOM), this study establishes that a total of 1.3 g of bulk sample from a single chondritic meteorite is sufficient to obtain a wide range of cosmochemical information, including light element analysis (H, C, and N), isotopic analysis (D/H, 13 C/ 12 C, and 15 N/ 14 N), and X-ray fluorescence spectroscopy for major elemental abundances. IOM isolated from the bulk meteorite samples was analyzed by light element and isotopic analysis as described above, 1 H and 13 C solid-state nuclear magnetic resonance spectroscopy, Raman spectroscopy, and complete noble gas analyses (abundances and isotopes). The samples studied included a pair from Murchison (CM2), one of which had been irradiated with high-energy X-rays in the course of computed tomographic imaging. No differences between the irradiated and non-irradiated Murchison samples were observed in the many different chemical and spectroscopic analyses, indicating that any X-ray–derived sample damage is below levels of detection. Elemental, isotopic, and molecular spectroscopic data derived from IOM isolated from the Sutter’s Mill sample reveals evidence that this meteorite falls into the class of heated CM chondrites.

planetary science↗
NASA NTRS2023

Ryugu Asteroid Sample Return Provides A Natural Laboratory for Primordial Chemical Evolution

The samples returned from near-Earth asteroid (162173) Ryugu provide a pristine record of the 4.6 billion years since the birth of the Solar System. The Hayabusa2 initial analysis team has integrated a range of analytical techniques to investigate Ryugu’s organic chemistry. Here, we highlight their latest findings, the potential questions which may be answered, and provide an overview of new prospects in the decade to come.

Asteroids↗
NASA NTRS2023

PAHs, Hydrocarbons, and Dimethylsulfides in Asteroid Ryugu Samples A0106 and C0107 and the Orgueil (CI1) Meteorite

Evaluating the molecular distribution of organic compounds in pristine extraterrestrial materials is cornerstone to understanding the abiotic synthesis of organics and allows us to better understand the molecular diversity available during the formation of our solar system and before the origins of life on Earth. In this work we identify multiple organic compounds in solvent extracts of asteroid Ryugu samples A0106 and C0107 and the Orgueil meteorite using two-dimensional gas chromatography and time-of-flight high resolution mass spectrometry (GC×GC-HRMS). Our analyses found similarities between the molecular distribution of organic compounds in Ryugu and the CI carbonaceous chondrite Orgueil. Specifically, several PAHs and organosulfides were found in Ryugu and Orgueil suggesting an interstellar and parent body origin for these compounds. We also evaluated the common relationship between Ryugu, Orgueil, and comets like Wild-2; however, until comprehensive compound-specific isotopic analyses for these organic species are undertaken, and until the effects of parent body processes and Earth’s weathering processes on meteoritic organics are better understood, their parent-daughter relationships will remain unanswered. Finally, the study of organic compounds in Ryugu samples and the curation practices for the future preservation of these unvaluable materials are also of special interest for future sample return missions, including NASA’s OSIRIS-REx asteroid sample return mission.

Hayabusa2↗
NASA NTRS2023

Extraterrestrial Amino Acids and Amines Identified in Asteroid Ryugu Samples Returned By the Hayabusa2 Mission

The hot water and acid extracts of two different Ryugu samples collected by the Hayabusa2 mission were analyzed for the presence of aliphatic amines and amino acids. The abundances and relative distributions of both classes of molecules were determined, as well as the enantiomeric compositions of the chiral amino acids. The Ryugu samples studied here were recovered from sample chambers A and C, which were composed of surface material, and a combination of surface and possible subsurface material, respectively. A total of thirteen amino acids were detected and quantitated in these samples, with an additional five amino acids that were tentatively identified but not quantitated. The abundances of four aliphatic amines identified in the Ryugu samples were also determined in the current work. Amino acids were observed in the acid hydrolyzed and unhydrolyzed hot water extracts of asteroid Ryugu regolith using liquid chromatography with UV fluorescence detection and high-resolution mass spectrometry. Conversely, aliphatic amines were only analyzed in the unhydrolyzed hot water Ryugu extracts. Two- to six-carbon (C 2 -C 6 ) amino acids with individual abundances ranging from 0.02 to 15.8 nmol g −1 , and one- to three-carbon (C 1 -C 3 ) aliphatic amines with individual abundances from 0.05 to 34.14 nmol g −1 , were found in the hot water extracts. Several non-protein amino acids that are rare in biology, including β-amino-n-butyric acid (β-ABA) and β-aminoisobuytric acid (β-AIB), were racemic or very nearly racemic, thus indicating their likely abiotic origins. Trace amounts of select protein amino acids that were enriched in the ւ-enantiomer may indicate low levels of terrestrial amino acid contamination in the samples. However, the presence of elevated abundances of free and racemic alanine, a common protein amino acid in terrestrial biology, and elevated abundances of the predominately free and racemic non-protein amino acids, β-ABA and β-AIB, indicate that many of the amino acids detected in the Ryugu water extracts were indigenous to the samples. Although the Ryugu samples have been found to be chemically similar to CI type carbonaceous chondrites, the measured concentrations and relative distributions of amino acids and aliphatic amines in Ryugu samples were notably different from those previously observed for the CI1.1 carbonaceous chondrite, Orgueil. This discrepancy could be the result of differences in the original chemical compositions of the parent bodies and/or alteration conditions, such as space weathering. In addition to α-amino acids that could have been formed by Strecker cyanohydrin synthesis during a low temperature aqueous alteration phase, β-, γ-, and δ-amino acids, including C 3 – C 5 straight-chain n-ω-amino acids that are not formed by Strecker synthesis, were also observed in the Ryugu extracts. The suite of amino acids measured in the Ryugu samples indicates that multiple amino acid formation mechanisms were active on the Ryugu parent body. The analytical techniques used here are well-suited to search for similar analytes in asteroid Bennu material collected by the NASA OSIRIS-REx mission scheduled for Earth return in September 2023.

Hayabusa2↗
NASA NTRS2022

Rapid Radiolytic Degradation of Amino Acids in the Martian Shallow Subsurface: Implications for the Search for Extinct Life

Amino acids are fundamental to life as we know them as the monomers of proteins and enzymes. They are also readily synthesized under a variety of plausible prebiotic conditions and are common in carbon-rich meteorites. Thus, they represent a reasonable class of organics to target in the search for prebiotic chemistry or chemical evidence of life on Mars. However, regardless of their origin, amino acids and other organic molecules present in near-surface regolith and rocks on Mars can be degraded by exposure to cosmic rays that can penetrate to a depth of a few meters. We exposed several pure amino acids in dry and hydrated silicate mixtures and in mixtures of silicates with perchlorate salts to gamma radiation at various temperatures and radiation doses representative of the martian near-subsurface. We found that irradiation of amino acids mixed with dry silica powder increased the rate of amino acid radiolysis, with the radiolysis constants of amino acids in silicate mixtures at least a factor of 10 larger compared with the radiolysis constants of amino acids alone. The addition of perchlorate salts to the silicate samples or hydration of silicate samples further accelerated the rate of amino acid destruction during irradiation and increased the radiolysis constants by a factor of *1.5. Our results suggest that even low-molecular-weight amino acids could degrade in just *20 million years in the top 10 cm of the martian surface regolith and rock, and even faster if the material contains elevated abundances of hydrated silicate minerals or perchlorates. We did not detect evidence of amino acid racemization after gamma radiation exposure of the samples, which indicates that the chirality of some surviving amino acids may still be preserved. Our experimental results suggest serious challenges for the search of ancient amino acids and other potential organic biosignatures in the top 2 m of the martian surface.

Alexander A. Pavlov↗
NASA NTRS2022

Non-Protein Amino Acids Identified in Carbon-Rich Hayabusa Particles

Amino acid abundances in acid-hydrolyzed hot water extracts of gold foils containing five Category 3 (carbon-rich) Hayabusa particles were studied using liquid chromatography with tandem fluorescence and accurate mass detection. Initial particle analyses using field emission scanning electron microscopy with energy-dispersive X-ray spectrometry indicated that the particles were composed mainly of carbon. Prior to amino acid analysis, infrared and Raman microspectroscopy showed some grains possessed primitive organic carbon. Although trace terrestrial contamination, namely L-protein amino acids, was observed in all Hayabusa extracts, several terrestrially uncommon non-protein amino acids were also identified. Some Hayabusa particles contained racemic (D≈L) mixtures of the non-protein amino acids β-aminoisobutyric acid (β-AIB) and β-amino-n-butyric acid (β-ABA) at low abundances ranging from 0.09 to 0.31 nmol g −1 . Larger abundances of the non-protein amino acid β-alanine (9.2 nmol g −1 , ≈4.5 times greater than background levels) were measured in an extract of three Hayabusa particles. This β-alanine abundance was ≈6 times higher than that measured in an extract of a CM2 Murchison grain processed in parallel. The comparatively high β-alanine abundance is surprising as asteroid Itokawa is similar to amino acid-poor LL ordinary chondrites. Elevated β-alanine abundances and racemic β-AIB and β-ABA in Hayabusa grains suggested these compounds have non-biological and plausibly non-terrestrial origins. These results are the first evidence of plausibly extraterrestrial amino acids in asteroid material from a sample-return mission and demonstrate the capabilities of the analytical protocols used to study asteroid Ryugu and Bennu samples returned by the JAXA Hayabusa2 and NASA OSIRIS-REx missions, respectively.

Eric T. Parker↗
NASA NTRS2021

Low total abundances and a predominance of n-ω-amino acids in enstatite chondrites: Implications for thermal stability of amino acids in the inner solar system

Investigating the organic contents of enstatite chondrite meteorites may offer insights into both early inner solar system and early Earth chemistry. Enstatite chondrite meteorites have highly reduced and anhydrous compositions, and their bulk isotopic compositions closely resemble terrestrial values, suggesting that their parent body asteroids accreted within the inner protoplanetary disk and were a primary contributor during Earth’s late accretion (Javoy, 1995; Piani et al., 2020). Here, we present the first report of amino acids in enstatite chondrite meteorite samples. Three EH3 meteorites were analyzed (Dominion Range [DOM] 14021, Larkman Nunatak [LAR] 12001, and Larkman Nunatak 06252). The acid-hydrolyzed water extracts of the meteorites contained low abundances (1.5–215.9 pmol per g) of n-ω-amino acids (glycine, β-alanine, γ-amino-n-butyric acid [γ- ABA], δ-amino-n-valeric acid [δ-AVA], and ϵ-amino-n-caproic acid [ϵ-ACA]), but amino acids were not present above detection limits in the nonhydrolyzed samples. The low amino acid abundances and the predominance of n-ω-amino acids resemble amino acid distributions previously observed for thermally altered chondrites. These results suggest that the parent body asteroid was not conducive to the synthesis and/or preservation of α-amino acids, or free amino acids in general, and that EH3 chondrite-like material may not have been a primary contributor of diverse or abundant free amino acids to the early Earth.

Danielle N. Simkus↗
NASA NTRS2021

Extraterrestrial hydroxy amino acids in CM and CR carbonaceous chondrites

The abundances, distributions, and enantiomeric ratios of a family of three- and four-carbon hydroxy amino acids (HAAs) were investigated in extracts of five CM and four CR carbonaceous chondrites by gas chromatography-mass spectrometry analyses. HAAs were detected in both the acid hydrolysates of the hot water extracts and the 6 M HCl extracts of all the CM and CR chondrites analyzed here with total hot water and HCl extractable HAA concentrations ranging from 6.94 to 315 nmol/g. The HAA analyses performed in this study revealed: (1) the combined (hot water + HCl) extracts of CR2 chondrites contained greater abundances of α-HAAs than that of CM2 chondrites and (2) the combined extracts of CM and CR chondrites contained roughly similar abundances of β- and γ-HAAs. Application of the new GC-MS method developed here resulted in the first successful chromatographic resolution of the enantiomers of an α-dialkyl HAA, d,l-α-methylserine, in carbonaceous chondrite extracts. Meteoritic α-methylserine was found to be mostly racemic within error and did not show l-enantiomeric excesses correlating with the degree of aqueous alteration, a phenomenon observed in meteoritic isovaline, another α-dialkyl amino acid. The HAAs identified in CM and CR chondrite extracts could have been produced during parent body alteration from the Strecker cyanohydrin reaction (for α-HAAs) and an ammonia-involved formose-like reaction (for β-, and γ-HAAs).

Amino acid(s)↗
NASA NTRS2021

The Impact and Recovery of Asteroid 2018 LA

The June 2, 2018 impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. Twenty-three meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as an HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g cm^(−3), a relatively low albedo pV ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth-impacting orbit via the ν6 resonance. The impact that ejected 2018 LA in an orbit toward Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U-Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb-Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.

Peter Jenniskens↗
NASA NTRS2021

Amino Acid Abundances and Compositions in Iron and Stony-Iron Meteorites

The organic compositions of carbonaceous chondrite meteorites have been extensively studied; however, there have been fewer reports of other meteorite classes, and almost none from iron meteorites, which contain much less carbon than carbonaceous chondrites but make up ~4% of observed meteorite falls. Here, we report the bulk amino acid content of three iron meteorites (Campo del Cielo, IAB; Canyon Diablo, IAB; and Cape York, IIIAB) and both the metal and silicate portions of a pallasite (Imilac). We developed a novel method to prepare the samples for analysis, followed by hot water extraction and analysis via liquid chromatography‐mass spectrometry. Free amino acid abundances ranging from 301 to 1216 pmol/g were observed in the meteorites, with the highest abundance in the silicate portion of the pallasite. Although some of the amino acid content could be attributed to terrestrial contamination, evidence suggests that some compounds are indigenous. A suite of C(5) amino acids was observed with a distinct distribution favoring a straight chain (n‐pentanoic acid) structure; this straight chain dominance is suggestive of that observed in thermally altered stony meteorites. Amino acids were also observed in terrestrial iron granules that were milled and analyzed in the same way as the meteorites, although the distribution of detected amino acids was different. It is possible that similar formation mechanisms existed in both the meteorites and the terrestrial iron, or that observed amino acids resulted from reactions of precursors during sample preparation. This work suggests that iron meteorites should not be overlooked for contributions of amino acids and likely other soluble organic molecules to the early Earth. Future studies of iron–nickel meteorites and asteroids, such as Psyche, may provide further insights into their potential organic inventory.

Jamie E. Elsila↗
NASA NTRS2020

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.

Aaron B. Regberg↗
NASA NTRS2020

A Sensitive Quantitative Analysis of Abiotically Synthesized Short Homopeptides using Ultraperformance Liquid Chromatography and Time-of-Flight Mass Spectrometry

In the origins of life field understanding the abiotic polymerization of simple organic monomers (e.g., amino acids) into larger biomolecules (e.g., oligopeptides), remains a seminal challenge. Recently, preliminary observations showed a limited set of peptides formed in the presence of the plausible prebiotic phosphorylating agent, diamidophosphate (DAP), highlighting the need for an analytical tool to critically evaluate the ability of DAP to induce oligomerization of simple organics under aqueous conditions. However, performing accurate and precise, targeted analyses of short oligopeptides remains a distinct challenge in the analytical chemistry field. Here, we developed a new technique to detect and quantitate amino acids and their homopeptides in a single run using ultraperformance liquid chromatography-fluorescence detection/time of flight mass spectrometry. Over an 8-minute retention time window, 18 target analytes were identified and quantitated, 16 of which were chromatographically separated at, or near baseline resolution. Compound identity was confirmed by accurate mass analysis using a 10 ppm mass tolerance window. This method featured limits of detection < 5 nM (< 1 fmol on column) and limits of quantitation (LOQs) <15 nM (< 3 fmol on column). The LODs and LOQs were upwards of ∼28x and ∼788x lower, respectively, than previous methods for the same analytes, highlighting the quantifiable advantages of this new method. Both detectors provided good quantitative linearity (R(exp 2) > 0.985) for all analytes spanning concentration ranges ∼3 - 4 orders of magnitude. We performed a series of laboratory experiments to investigate DAP-mediated oligomerization of amino acids and peptides and analyzed experimental products with the new method. DAP readily polymerized amino acids and peptides under a range of simulated environmental conditions. This research underscores the potential of DAP to have generated oligopeptides on the primordial Earth, enhancing prebiotic chemical diversity and complexity at or near the origin of life.

Prebiotic Chemistry and Analytical Chemistry↗
NASA NTRS2019

Outgassing From the OSIRIS-REx Sample Return Capsule: Characterization and Mitigation

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft launched on September 8, 2016, beginning a seven-year journey to return at least 60 g of asteroid material from (101955) Bennu to Earth. During the outbound cruise, Doppler tracking of the spacecraft observed a small but measurable acceleration when the sample return capsule (SRC) was first placed in sunlight. Subsequent analysis determined that outgassing from the SRC is the most likely cause for the acceleration. This outgassing received combined engineering and scientific attention because it has potential implications both for spacecraft navigation performance and for contamination of the collected samples. Thermal modeling, laboratory studies of SRC materials, and monitoring of the acceleration are all consistent with H2O as the main component of the outgassing. Dedicated, in-flight campaigns continued to expose the SRC to sunlight until the acceleration dropped to the acceleration noise floor. Any residual amounts of H2O outgassing are not considered to be a hazard with regards to mission operations or pristine sample acquisition. The sample stow procedure has been updated to ensure that no direct line of site exists between any residual outgassing and the samples during future operations. Similar outgassing of the Stardust SRC probably also occurred. No adverse contamination of Stardust samples was observed that could be associated with this process. Future missions that use similar reentry vehicles should consider procedures to test for and, if necessary, mediate such outgassing after launch.

Origins, Spectral Interpretation, Resource Identif↗
NASA NTRS2019

Outgassing From the OSIRIS-REx Sample Return Capsule: Characterization and Mitigation

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft launched on September 8, 2016, beginning a seven-year journey to return at least 60 g of asteroid material from (101955) Bennu to Earth. During the outboundcruise, Doppler tracking of the spacecraft observed a small but measurable acceleration when the sample return capsule (SRC) was first placed in sunlight. Subsequent analysis determined that outgassing from the SRC is the most likely cause for the acceleration. This outgassing received combined engineering and scientific attention because it has potential implications both for spacecraft navigation performance and for contamination of the collected samples. Thermal modeling, laboratory studies of SRC materials, and monitoring of the acceleration are all consistent with H2O as the main component of the outgassing. Dedicated, in-flight campaigns continued to expose the SRC to sunlight until the acceleration dropped to the acceleration noise floor. Any residual amounts of H2O outgassing are not considered to be a hazard with regards to mission operations or pristine sample acquisition. The sample stow procedure has been updated to ensure that no direct line of site exists between any residual outgassing and the samples during future operations. Similar outgassing of the Stardust SRC probably also occurred. No adverse contamination of Stardust samples was observed that could be associated with this process. Future missions that use similar reentry vehicles should consider procedures to test for and, if necessary, mediate such outgassing after launch.

Scott A Sandford↗
NASA NTRS2019

The CM carbonaceous chondrite regolith Diepenveen

A carbonaceous chondrite was recovered immediately after the fall near the village of Diepenveen in the Netherlands on October 27, 1873, but came to light only in 2012. Analysis of sodium and poly-aromatic hydrocarbon content suggests little contamination from handling. Diepenveen is a regolith breccia with an overall petrology consistent with a CM classification. Unlike most other CM chondrites, the bulk oxygen isotopes are extremely (16)O rich, apparently dominated by the signature of anhydrous minerals, distributed on a steep slope pointing to the domain of intrinsic CM water. A small subset plots closer to the normal CM regime, on a parallel line 2 ‰ lower in δ(17)O. Different lithologies in Diepenveen experienced varying levels of aqueous alteration processing, being less aqueously altered at places rather than more heated. The presence of an agglutinate grain and the properties of methanol-soluble organic compounds point to active impact processing of some of the clasts. Diepenveen belongs to a CM clan with ~5 Ma CRE age, longer than most other CM chondrites, and has a relatively young K-Ar resetting age of ~1.5 Ga. As a CM chondrite, Diepenveen may be representative of samples soon to be returned from the surface of asteroid (162173) Ryugu by the Hayabusa2 spacecraft.

Marco Langbroek↗
NASA NTRS2015

Effect of a Synchrotron X-ray Microtomography Imaging Experiment on the Amino Acid Content of a CM Chondrite

X-ray microcomputed tomography and synchrotron X-ray microcomputed tomography (μCT) are becoming popular tools for the reconnaissance imaging of chondrites. However, there are occasional concerns that the use of μCT may be detrimental to organic components of a chondrite. Soluble organic compounds represent ~2–10% of the total solvent extractable carbon in CI and CM carbonaceous chondrites and amino acids are among the most abundant compounds in the soluble organic fraction. We irradiated two samples of the Murchison CM2 carbonaceous chondrite under conditions slightly harsher (increased beam exposure time) than those typically used for x-ray μCT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed control sample occurred. After subjecting two meteorite portions to ionizing radiation dosages of 1.1 kiloGray (kGy) and 1.2 kGy with 48.6 and 46.6 keV monochromatic X-rays, respectively, we analyzed the amino acid content of each sample. Within analytical errors, we found no differences in the amino acid abundances or enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We show with calculations that any sample heating due to x-ray exposure is negligible. We conclude that a monochromatic synchrotron X-ray μCT experiment at beamline 13-BM-D of the Advanced Photon Source, which imparts ~1 kGy doses, has no detectable effect on the amino acid content of a carbonaceous chondrite. These results are important for the initial reconnaissance of returned samples from the OSIRIS-REx and Hayabusa 2 asteroid sample return missions.

Jon M. Friedrich↗