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NASA NTRSDate not supplied

Coordinated analyses of hydrated Kuiper Belt dust

We report on coordinated mineralogical, chemical, and isotopic analyses of hydrated carbon-rich interplanetary dust particles (IDPs). We focus on hydrated IDPs that contain high solar flare track densities consistent with an origin in outer Solar System bodies such as Edgeworth-Kuiper belt objects (EKBOs) [1]. We are searching for evidence of the heavy water reservoir predicted by self-shielding models [2]. The IDPs were embedded in sulfur and microtome thin sections were obtained for Fourier-transform infrared (FTIR), transmission electron microscopy (TEM), and nanoSIMS analyses. The IDPs were only partly microtomed and the remainder was extracted from the sulfur and pressed into In or Au for high precision O isotopic analyses. The hydrated IDPs in this study are compact low-porosity objects with a mineralogy dominated by fine-grained saponite and lesser serpentine, Fe-Ni sulfides, Mg-Fe carbonates, rare crystaline silicates, and abundant organic matter. The C in the IDPs is abundant (typically >4X CI) and occurs as isolated nanoglobules and finely disseminated within the phyllosilicate matrix of the IDPs. TEM analyses of the nanoglobules show O-rich, S-depleted rims with higher carbonyl functionality than their cores. FTIR spectra show strong aliphatic C-H stretches consistent with the presence of short-chain aliphatic hydrocarbons in these IDPs. The oxygen isotopic compositions measured in 6 IDPs all plot within error of the CCAM line [3]. For several of the IDPs we were able to obtain multiple analyses. The ∆^(17)O values range from -23‰ up to +3.4‰ with most analyses clustering above the terrestrial fractionation line. The O isotopic compositions and the high C contents of these IDPs are distinct from known hydrated carbonaceous chondrites. The track-rich hydrated IDPs record parent body aqueous alteration effects through interactions with 16O-poor H2O on a EKBO parent body. The aqueous alteration activity likely resulted from the heat generated by collisional processes among EKBOs given that these objects are believed to have accreted late after the decay of 26Al [4].

Lindsay P. Keller↗
NASA NTRS2021

The abundances of F, Cl, and H2O in eucrites: Implications for the origin of volatile depletion in the asteroid 4 Vesta

We conducted a petrologic study of apatite within eight unbrecciated, non-cumulate eucrites and two monomict, non-cumulate eucrites. These data were combined with previously published data to quantify the abundances of F, Cl, and H2O in the bulk silicate portion of asteroid 4 Vesta (BSV). Using a combination of apatite-based melt hygrometry/chlorometry and appropriately paired volatile/refractory element ratios, we determined that BSV has 3.0–7.2 ppm F, 0.39–1.8 ppm Cl, and 3.6–22 ppm H2O. The abundances of F and H2O are depleted in BSV relative to CI chondrites to a similar degree as F and H2O in the bulk silicate portion of the Moon. This degree of volatile depletion in BSV is similar to what has been determined previously for many moderately volatile elements in 4 Vesta (e.g., Na, K, Zn, Rb, Cs, and Pb). In contrast, Cl is depleted in 4 Vesta by a greater degree than what is recorded in samples from Earth or the Moon. Based on the Cl-isotopic compositions of eucrites and the bulk rock Cl/F ratios determined in this study, the eucrites likely formed through serial magmatism of a mantle with heterogeneous δ37Cl and Cl/F, not as extracts from a partially crystallized global magma ocean. Furthermore, the volatile depletion and Cl-isotopic heterogeneity recorded in eucrites is likely inherited, at least in part, from the precursor materials that accreted to form 4 Vesta and is unlikely to have resulted solely from degassing of a global magma ocean, magmatic degassing of eucrite melts, and/or volatile loss during thermal metamorphism. Although our results can be reconciled with the past presence of wide-scale melting on 4 Vesta (i.e., a partial magma ocean), any future models for eucrite petrogenesis involving a global magma ocean would need to account for the preservation of a heterogeneous eucrite source with respect to Cl/F ratios and Cl isotopes.

Francis M. Mccubbin↗
NASA NTRSDate not supplied

Soluble Organic Matter (SOM) analysis of the Hayabusa2 samples: The first results

The Hayabusa2 spacecraft successfully collected the surface and possible sub-surface materials of the asteroid 162173 Ryugu. Ryugu is a C-type asteroid characterized by a low-albedo surface probably consisting of hydrous minerals and carbonaceous materials. [1] The direct optical and spectral analysis of the returned samples indicates that Ryugu material is dominated by hydrous carbonaceous chondrite-like matter (similar to CI chondrites) [2]. Since carbonaceous chondrites have generally yielded various types of organic matter, the collected Ryugu grains are expected to contain diverse types of organic compounds including bio-related molecules. The occurrence of organic compounds in the Ryugu surface will provide clues to the evolution of prebiotic molecules and their preservations associated with aqueous alteration of the primitive asteroid. The initial analysis of soluble organic matter (SOM) of the Hayabusa2-returned samples has been performed by an international team consisting of 32 members. Because the sample amount available for comprehensive SOM analyses is limited, and because the SOM is expected to be present as a complex mixture of various types of organic compounds with very small concentrations of each compound, high-sensitivity and high-resolution analytical techniques have been developed using carbonaceous meteorites [e.g. 3]. Two aggregate samples of the Ryugu grains (A106 and C107) were allocated for the solvent extractions and bulk carbon (C), hydrogen (H), nitrogen (N), sulfur (S) and oxygen (O) measurements. The A106 sample was collected during the 1st sampling in February 2019 and the C107 sample was collected during the 2nd sampling in July 2019 after the Small Carry Impactor (SCI) operation. They consist mainly of particles smaller than 1 mm in diameter, and each sample mass was 38-39 mg. They were firstly investigated spectroscopically in the near infrared wavelength range by the Stone Team prior to the solvent extractions. Other small grains (A0080 and C0057) were also allocated for this study to investigate the spatial distribution of organic compounds on the sample surface. The extraction and analytical measurements implemented by the SOM Team are summarized in Figure 1. Each powder sample was extracted sequentially with non-polar to polar solvents, i.e., hexane, dichloromethane (DCM), methanol (MeOH) and H2O, for non-targeted analysis to reveal the compound composition. Each solvent extract was analyzed by solution state nuclear magnetic resonance (NMR) spectroscopy [4], Fourier transform- ion cyclotron resonance/mass spectrometry (FT-ICR/MS) with ESI and APPI ionization [5] and by high-resolution mass spectroscopy using Orbitrap MS coupled with nano-liquid chromatography (nanoLC/Orbitrap MS) [6], and using two dimensional gas chromatography/mass spectrometry (GC×GC/MS). The extracted residues were passed to the Chemistry Team for further inorganic element analysis. The other powder sample was subjected to the hot water extraction for amino acid analyses including chiral isomer separation, which was performed by three-dimensional (3D) high-performance liquid chromatography (HPLC) with high-sensitivity fluorescence detection (FD) [7] and by HPLC/FD coupled with quadrupole-time of flight/mass spectrometry (QToF/MS) [8]. After the hot water extraction, the residue was split into two halves. One half was further extracted with hydrochloric acid (HCl) to analyze for amino acids in bound-form. The other half was sequentially extracted with DCM/MeOH (1/1) to analyze semi-polar compounds such as polycyclic aromatic hydrocarbons (PAHs) by GC/MS, followed by further extraction with formic acid to analyze polar heterocyclic compounds, and subsequent extraction with HCl to detect bound-form polar compounds. The extracted residues were passed to the IOM Team for the analysis of insoluble organic matter (IOM). Compound-specific stable isotope analyses will be performed using GC/combustion/isotope ratio mass spectrometry (GC/C/IRMS) if the compound concentration is high enough to enable such an isotopic measurement. All extraction procedures were performed on an ISO 6 (Class 100) clean bench inside an ISO 5 (Class 1000) clean room. Baked serpentine powder was also analyzed as a procedural blank. In situ organic compound analysis with the molecular imaging was performed using desorption electrospray ionization (DESI) equipped with Orbitrap MS [9, 10], followed by spatial imaging of organic compounds using ToF/secondary ion mass spectrometry (ToF/SIMS) [11]. The bulk chemical and isotopic compositions of CNS and HO were determined using nano-elemental analysis/isotope ratio mass spectrometry (nanoEA/IRMS) [12] and EA/pyrolysis/IRMS, respectively. We have identified a variety of indigenous organic compounds in the extracts of both A106 and C107 samples. The Ryugu grains host organic molecules under the high-vacuum and cosmic-ray irradiation environment of the asteroid surface. The analysis of extracted molecules is in progress, and the first results will be presented at the symposium.

Hiroshi Naraoka↗
NASA NTRSDate not supplied

Organic Matter in Itokawa Particles

The first Hayabusa mission returned samples from the near-Earth S-type asteroid 25143 Itokawa to Earth in 2010[1]. Although Itokawa has a lithology related to ordinary chondrites(OCs) that typically have low organic contents, several Itokawa particles were found to contain organic matter (OM)[2-5]. However, there was not an explicit conclusion to the origin of the observed OMin these early studies. We have extended our search for OM into other Itokawa grains. Here, we report extraterrestrial OM (macromolecular carbon and amino acids) observed in six Itokawa particles(including a category1 particle: RA-QD02-0162[#62; also nicknamed “Amazon”],and five category3 carbon-rich particles:RA-QD02-0012[#12], RA-QD02-0078[#78], RB-CV-0029[#29], RB-CV-0080 [#80] and RB-QD04-0052[#52]).All allocated Itokawa samples were initially analysed by spot and point-by-point mapping Raman spectroscopic analysis at the Open University, UK. Amazon was then transferred and mounted into indium on an aluminium stub, which was studied with a NanoSIMS 50L ion microprobe for its H,C,N isotopic compositions. The rest of the samples were mounted in sterile gold foils, and the amino acid contents of their acid hydrolysed hot water extracts were obtained with a liquid chromatography with tandem fluorescence and accurate mass detection at NASA Goddard Space Flight Center, USA. Based on the observation of the Raman parameters(e.g. the peak locations and widths of the defect (D) and graphite (G) bands)[6], a significant variety of carbonaceous materials has been observed in Amazon. The carbonaceous materials include primitive and unaltered OM that shares similarity with the IOM in primitive (CI,CM,CR) carbonaceous chondrites, as well as OM that has been heavily graphitised. The organic structure of the heated material is best represented by nanocrystalline graphite, comparable to that observed for metamorphosed meteorites (e.g., L3–6 Inman, Tieschitz and New Concord,CV3 Allende, and EH4 Indarch),suggesting peak metamorphic temperatures (PMT) of >~600°C. The thermal history recorded in the graphitic OM agrees with PMT estimates for returned Itokawa regolith grains (600–800°C)[7].We have obtained the H,C,N isotopic compositions for the primitive OM in Amazon, which exhibits unambiguously extraterrestrial isotopic signatures (δD = +4868±2288‰; δ13C = −24±5‰; δ15N = +344±20‰), contrasting to the typically negative isotopic values obtained for terrestrial organic matter[8]. The δD and δ13C values of the organic material in Amazon are comparable to OCs, however, the δ15N value is higher than that typically observed for OCs (δ15N = −47 to +36‰), and is similar to that of CRs (δ15N = +153 to +309‰)[9].Our data suggest a genetic link between the primitive organic material observed in Itokawa to CRs and IDPs for they share similar D, 13C and 15N enrichments[10].The high carbon contents of the five category 3 Itokawa particles suggest potentially higher OM abundances, hence we extracted and analysed amino acids in these samples. Although terrestrial contamination was observed primarily as L-protein amino acids, several terrestrially uncommon non-protein amino acids were also observed at low abundances, such as β-aminoisobutyric acid (β-AIB),β-amino-n-butyric acid (β-ABA), and β-alanine. Itokawa amino acid content observed here was dissimilar to thermally altered OCs, but preliminarily analogous to more aqueously altered CR2s.Continued evolution of Itokawa is evident by the in fall of primitive organic material derived from CRs/IDPs, accounting for a complex interplay between the remnant Itokawa silicates with exogenous organics. The results reported here are the first evidence of extraterrestrial OM in asteroid material from a sample-return mission, showcasing a working protocol for analysing samples returned by the Hayabusa2 and OSIRIS-REx missions

Q. H. S. Chan↗
NASA NTRS2022

The Lithophile Element Budget of Earth’s Core

The relative composition of Earth’s core and mantle were set during core formation. By determining how elements partition between metal and silicate at high pressures and temperatures, measurements of the mantle composition and geophysical observations of the core can be used to understand the mechanisms by which Earth formed. Here we present the results of metal–silicate partitioning experiments for a range of nominally lithophile elements (Al, Ca, K, Mg, O, S, Si, Th, U) and S to 85 GPa and up to 5400 K. With our results and a compilation of literature data, we developed a parameterization for partitioning that accounts for compositional dependencies in both the metal and silicate phases. Using this parameterization in a range of planetary growth models, we find that, in general, lithophile element partitioning into the metallic phase is enhanced at high temperatures. The relative abundances of FeO, SiO2 and MgO in the mantle vary significantly between planetary growth models, and the mantle abundances of these elements can be used to provide important constraints on Earth’s accretion. To match Earth’s core mass and mantle composition, Earth’s building blocks must have been enriched in Fe and depleted in Si compared with CI chondrites. Finally, too little Mg, Si and O are partitioned into the core for precipitation of oxides to be a major source of energy for the geodynamo. In contrast, several ppb of U can be partitioned into the core at high temperatures, and this energy source must be accounted for in thermal evolution models.

dynamo↗
NASA NTRS2022

The Abundances of F, Cl, and H2O in 4Vesta from Eucrites

The abundance and distribution of magmatic volatiles (i.e., H, C, N, F, S, and Cl) within the silicate portion of a differentiated planetary body has important consequences on its thermochemical evolution. However, the abundances of magmatic volatiles within differentiated bodies are difficult to quantify, and they are often depleted by varying degrees relative to CI chondrites. The mechanisms of depletion are not well constrained and could relate to intrinsic volatile depletion of the building blocks that formed the bodies, high temperature processes that result from accretion, post-accretion loss through parent body geological processes and large-scale impacts, and/or redistribution within a parent body through processes like core formation [1–4]. In the present study, we aim to constrain the abundances of F, Cl, and H2O in eucrites to better understand the magnitude of volatile depletion on 4Vesta. To accomplish this objective, we report electron microprobe analyses of apatite from seven unbrecciated, non-cumulate eucrites (i.e., CMS 04049,GRA 98098, LEW 88010, MAC 02522, MAC 041169,QUE 94484, and QUE 97053) and two monomict, non-cumulate eucrites (i.e., Berthoud and Stannern). In combination with previously published data on eucrite-hosted apatite, we determine Cl/F and H2O/F ratios in bulk rock eucrites through the application of apatite-based melt hygrometry and chlorometry [e.g., 5–7].Additionally, we estimate the bulk rock abundances of F in six non-cumulate eucrites (i.e., GRA 98098, MAC041169, PCA 91078, QUE 97053, Stannern, and Berthoud), which we combine with previously published bulk rock F data on non-cumulate eucrites[8] to constrain the abundances of F, Cl, and H2O in 4Vesta using appropriately paired volatile/refractory element ratios for F, followed by Cl/F and H2O/F ratios for Cl and H2O, respectively.

F M McCubbin↗
NASA NTRSDate not supplied

Extraterrestrial Amino Acids in the C2 Ungrouped Carbonaceous Chondrite Tarda: A Unique Distribution

Introduction: Meteorites provide a record of the chemical processes that occurred in the early solar sys-tem. The delivery of organic matter by carbonaceous chondrites to the early Earth could have been an im-portant source of amino acids and other prebiotic or-ganic molecules required for the emergence of life [1]. To date, 96 amino acids have been named in meteor-ites, most of which are rare or absent in the biosphere [2]. The variability in amino acid concentrations and isomer distributions measured in carbonaceous chon-drites can be explained by differences in parent body chemistry and alteration conditions [3]. In addition, aqueous alteration was likely important in the amplifi-cation of some left-handed amino acids over their right-handed forms (L-excesses up to ~60%) in the Tagish Lake meteorite [3], suggesting that the origin of life on Earth and possibly elsewhere in the solar sys-tem was biased towards L-amino acids. On August 25, 2020, a fireball was witnessed in southern Morocco and the first pieces of the meteorite fall were recovered the following day near the town of Tarda [4]. Thousands of individual fragments were recovered from the strewn field totaling ~4 kg [4]. Based on petrographic observations, bulk mineralogy, and chemical and O-isotopic analyses, Tarda has been classified as a C2 ungrouped carbonaceous chondrite with similarities to Tagish Lake (though more primi-tive), as well as CI, CY, and CR chondrites [4,5]. The fall and rapid recovery of the Tarda stones provide an important opportunity to investigate a C-rich meteorite using the state-of-the-art techniques that will also be used to study the samples returned from asteroids Ryugu and Bennu by the Hayabusa2 and OSIRIS-REx missions, respectively. Here, we report the first amino acid analyses of the Tarda meteorite. The total concentrations, enantio-meric ratios and relative distributions of amino acids were determined using ultrahigh performance liquid chromatography with UV fluorescence and time-of-flight mass spectrometry (LC-FD/ToF-MS) at NASA GSFC. This analytical technique was employed on extracts from two different pre-rain Tarda meteorite fragments and a sample of sand collected from the Tarda fall site for the purpose of assessing potential terrestrial contamination. Bulk H, C, and N elemental and isotopic analyses were also conducted at the Car-negie Institution for Science (CIS) to assist with petro-logic type classification using elemental analysis iso-tope ratio mass spectrometry (EA-IRMS).

D P Glavin↗
NASA NTRSDate not supplied

Aqueous Alteration on the Ryugu Parent Body Constrained by Chemical Equilibrium Models

The composition of solid samples returned from the asteroid 162173 Ryugu byHayabusa2 indicates aqueous alteration of rocks that formed a parent body of Ryugu [1, 2]. As on parent bodies of carbonaceous chondrites [3-5], Ryugu materials could have went through (1) accretion of anhydrous and reduced rocky grains together with water-rich ices, (2) melting of ices in the body’s interior through release of radiogenic heat [6], and (3)aqueous alteration of rocky and organic materials that produced secondary minerals, salt- and organic-bearing water solutions, gases, and altered organic matter. Although the bulk chemical composition and major mineralogy (phyllosilicates, magnetite, pyrrhotite, carbonates, phosphates, etc.) of Ryugu [1,2]are similar to those of CI carbonaceous chondrites [3-5, 7], the lack of sulfates and a deficiency of oxygen in the returned samples suggest a distinct alteration pathway. Chondritic materials [3-5] do not indicate complete chemical equilibration though low-temperature parent body processes. However, calculations of chemical equilibria in modeling rock-water-gas type systems[e.g., 8, 9], could assess deviations of chondritic materials from equilibrium conditions and constrain partitioning of chemical elements between solid, aqueous, and gas phase for different stages of alteration. Here we constrained speciation of solid, aqueous, and gaseous phases during aqueous alteration on the Ryugu parent body through chemical equilibrium calculations.

M Yu Zolotov↗
NASA NTRSDate not supplied

Aqueous alteration of Cb-type asteroid Ryugu

The samples from the asteroid Ryugu, which returned to Earth in the winter of 2020 [1], were stored under pure Nitrogen conditions at the Extraterrestrial Materials Curation Center of ISAS. After basic description [2-3], they were distributed to six initial analysis teams in Japan in June 2021. The initial analysis "Stone" team, which was responsible for the analysis of coarse particles (>1 mm in size), consisted of about 150 scientists from Japan and abroad, and conducted a series of analyses We analyzed sixteen coarse Ryugu particles 1 ~ 8 mm in size: six from the 1st touch-down site and ten from the 2nd touch-down site. Individual coarse samples were cut by Xe-FIB or wire-saw to expose particular objects or textures to be exposed on the surface based on 3D structure and element distribution obtained by synchrotron X-ray CT analysis and XRF analysis, respectively. FE-SEM/EDS and FE-EPMA/WDS analysis were made on all polished sections. TEM observation of many FIB sections was made to see microstructures and to compare with carbonaceous chondrites. Many other analyses were carried out to characterize mineralogical and compositional properties and summary of the analysis procedures is described in [4]. X-ray CT analysis showed that all sixteen Ryugu particles are composed of fine-grained material, with no chondrules and CAIs larger than 100 μm in size. FE-EPMA observation showed that Ryugu samples are breccias, consisting of many small rock fragments of different compositions, lithologies, and histories. The most common lithology includes Mg-rich saponite and serpentine, dolomite, magnesite, hydroxyapatite, pyrrhotite, and magnetite as main constituents. The mineralogy of this major lithology supports the classification of Ryugu samples as CI chondrites, which experienced extensive aqueous alteration in Ryugu’s parent asteroid. Based on the obtained mineralogical properties, we performed chemical modeling of aqueous alteration of Ryugu’s parent asteroid [5]. Numerical simulations [6-8] to reproduce thermal history and impact-induced destruction of the Ryugu’s parent asteroid were also carried out using mineralogical and physical properties of the Ryugu samples. In the talk, I would like to explain the conditions of aqueous alteration occurred in the parent asteroid of Ryugu in order to show how the water in the asteroid changed the mineralogy and chemistry of the nebular dust.

T. Nakamura↗
NASA NTRSDate not supplied

Regolith Processes Revealed by Carbonaceous Chondrites with Implications for Asteroids Ryugu and Bennu, and the Martian Moon Phobos

C-complex asteroids frequently exhibit reflectance spectra consistent with thermally metamorphosed or shocked carbonaceous chondrites and brecciation. Petrographic evidence of impact shock melting and brecciation has been presented for CM and CI chondrites, which we review here as a reminder of what we expect in the returned Ryugu, Bennu and Phobos samples.

Michael Zolensky↗
NASA NTRS2022

Pre- and Post-Production Processes Increasingly Dominate Greenhouse Gas Emissions From Agri-Food Systems

We present results from the FAOSTAT emissions shares database, covering emissions from agri-food systems and their shares to total anthropogenic emissions for 196 countries and 40 territories for the period 1990–2019. We find that in 2019, global agri-food system emissions were 16.5 (95 %; CI range: 11–22) billion metric tonnes (GtCO2 eq. yr(exp -1)), corresponding to 31%(range: 19 %–43 %) of total anthropogenic emissions. Of the agri-food system total, global emissions within the farm gate – from crop and livestock production processes including on-farm energy use – were 7.2 GtCO2 eq. yr(exp -1); emissions from land use change, due to deforestation and peatland degradation, were 3.5 GtCO2 eq. yr(exp -1); and emissions from pre- and post-production processes – manufacturing of fertilizers, food processing, packaging, transport, retail, household consumption and food waste disposal – were 5.8 GtCO2 eq. yr(exp -1). Over the study period 1990–2019, agri-food system emissions increased in total by 17 %, largely driven by a doubling of emissions from pre- and post-production processes. Conversely, the FAOSTAT data show that since 1990 land use emissions decreased by 25 %, while emissions within the farm gate increased 9 %. In 2019, in terms of individual greenhouse gases (GHGs), pre- and postproduction processes emitted the most CO2 (3.9 GtCO2 yr(exp -1)), preceding land use change (3.3 GtCO2 yr(exp -1)) and farm gate (1.2 GtCO2 yr(exp -1)) emissions. Conversely, farm gate activities were by far the major emitter of methane (140 MtCH4 yr(exp -1)) and of nitrous oxide (7.8 MtN2Oyr(exp -1)). Pre- and post-production processes were also significant emitters of methane (49 MtCH4 yr(exp -1)), mostly generated from the decay of solid food waste in landfills and open dumps. One key trend over the 30-year period since 1990 highlighted by our analysis is the increasingly important role of food-related emissions generated outside of agricultural land, in pre- and post-production processes along the agri-food system, at global, regional and national scales. In fact, our data show that by 2019, pre- and post-production processes had overtaken farm gate processes to become the largest GHG component of agri-food system emissions in Annex I parties (2.2 GtCO2 eq. yr(exp -1)). They also more than doubled in non-Annex I parties (to 3.5 GtCO2 eq. yr(exp -1)), becoming larger than emissions from land use change. By 2019 food supply chains had become the largest agri-food system component in China (1100 MtCO2 eq. yr(exp -1)), the USA (700 MtCO2 eq. yr(exp -1)) and the EU-27 (600 MtCO2 eq. yr(exp -1)). This has important repercussions for food-relevant national mitigation strategies, considering that until recently these have focused mainly on reductions of non-CO2 gases within the farm gate and on CO2 mitigation from land use change. The information used in this work is available as open data with DOI https://doi.org/10.5281/zenodo.5615082 (Tubiello et al., 2021d). It is also available to users via the FAOSTAT database (https://www.fao.org/faostat/en/#data/EM; FAO, 2021a), with annual updates.

FAOSTAT agri-food systems emissions database↗
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↗
NASA NTRSDate not supplied

Spectral and Mineralogical Analyses of Aguas Zarcas in Search of Its Parent Body

Aguas Zarcas is an intriguing carbonaceous chondrite that fell in Aguas Zarcas district, San Carlos, Alajulea, Costa Rica on 23 April 2019 [1]. This carbonaceous chondrite was found to be a breccia at al all scales with diverse lithologies (metal-rich, brecciated CM, and CI) [2]. Here we present spectroscopic and PSD-XRD analyses of a sample of Aguas Zarcas(donated to NASA JSC by Robert Ward) to better understand the origin and parent body for this meteorite. The spectral and mineralogical analyses are placed in the context of the published petrological and geochemical analyses of Aguas Zarcas, and its spectra are compared to a suite of spectra of asteroidal materials, including cabon-bearing asteroids, asteroid returned samples, and carbonaceous chondrites. The focus of this investigation will be on hydrated minerals and carbon-bearing materials, including organics and carbonates.

D. Takir↗
NASA NTRSDate not supplied

Oxygen isotopic mapping of a clast in fragment C0002 from asteroid Ryugu

The samples of Ryugu returned by the Hayabusa2 spacecraft have mineralogy similar to CI chondrites and are dominated by secondary phases(e.g., phyllosilicates, carbonates, magnetite, sulfides) from extensive parent body aqueous alteration. Anhydrous minerals such as olivine, pyroxene, and spinel are rare and exist in phyllosilicate-rich clasts [2-4]. Oxygen isotopic studies of these minerals have shown a bimodal distribution with both 16O-rich and 16O-poor grains. In this study, we conducted NanoSIMS isotopic mapping of a clast found in a fragment of a C0002 grain from Chamber C, which may have derived from the asteroid sub-surface, to characterize small primary minerals

A N Nguyen↗
NASA NTRS2022

GRO 95577 (CR1) as a mineralogical analogue for asteroid (101955) Bennu

Orbital spectra of asteroid (101955) Bennu collected by NASA's Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS–REx) spacecraft have identified ungrouped C, CI, and CM meteorites having petrologic types 1, 1/2, and 2 as the best mineralogical analogues to Bennu to date. Here we present spectral evidence that Grosvenor Mountains (GRO) 95577, a CR1, is a better analogue for Bennu's bulk surface mineralogy. CR-like parent bodies are targets of interest because they contain some of the most pristine materials from the solar nebula and can contain substantial amounts of H2O and OH− in addition to exotic organics. Unfortunately, terrestrial weathering makes constraining their indigenous mineralogy and organics challenging. Analysis of samples retrieved directly from an asteroid would help us disentangle the effects of terrestrial weathering and asteroidal aqueous alteration and hence whether some of the exotic organics and large populations of presolar grains were affected by terrestrial processes in meteorites. If Bennu is comprised of CR1(−like) material, in whole or in part, the OSIRIS–REx returned sample represents a tremendous opportunity to explore in depth what is currently a unique material among carbonaceous chondrites.

Asteroids↗
NASA NTRS2022

Lithological variation of asteroid Ryugu samples returned by the Hayabusa 2 spacecraft: Assessment from the 18 particles distributed to the initial analysis “Stone” team

JAXA’s Hayabusa2 spacecraft successfully returned~5.4g of C-type asteroid Ryugu materials on Dec. 2020 [e.g., 1] and the recovered samples were extensively analyzed by initial analysis teams and Phase2 curation teams. The reported results show that Ryugu samples are similar to CI chondritesin chemistry and mineralogy, showing evidence for aqueous alteration in the parent body [e.g., 2,3]. As a “stone” team of the initial analysis, we received 18coarse particles (>1 mm) of Ryugu samples to characterize their mineralogy and petrology. We found that the samples were breccias of mm-to-sub mm size clasts. All of the clasts are mainly composed of Mg-Fe phyllosilicates, but the alteration degree appears slightly different from one clast to another. Here we report a lithological variation of Ryugu samples to propose their reasonable lithological classification based upon different mineral assemblages and to discuss the formation and evolution of the Ryugu parent body.

Michael E Zolensky↗
NASA NTRS2022

Mapping Phyllosilicates on the Asteroid Bennu Using Thermal Emission Spectra and Machine Learning Model Applications

Bennu, the target of the OSIRIS-REx mission, is an asteroid with compositions analogous to low petrologic type CI, CM, CR, and/or ungrouped carbonaceous chondrites. Asteroids like Bennu provide information about the building blocks of the early Solar System. Analysis of the mid-infrared remote sensing data informs mineral quantification. We apply a phyllosilicate specific model, developed by Breitenfeld et al. (2021) that distinguishes between Mg and Fe serpentines, to Baseball Diamond 1 (BBD1), Equatorial Station 3 (EQ3), and Touch-And-Go OSIRIS-REx Thermal Emission Spectrometer data. The average total phyllosilicate predictions are 73 (BBD1) and 72 vol% (EQ3). We observe higher Fe-cronstedtite and lower Mg-rich serpentine content in the equatorial region of Bennu than average. Mid-infrared spectral variability may be explained by sorting effects through mass movement.

Bennu↗
NASA NTRS2023

Early Fluid Activity on Ryugu Inferred By Oxygen, Carbon, and 53Mn-53Cr Isotopic Analyses of Carbonates and Magnetite

Samples from asteroid Ryugu returned by the Hayabusa2 mission contain evidence of extensive alteration by aqueous fluids and appear related to the CI chondrites. To understand the sources of the fluid and the timing of chemical reactions occurring during the alteration processes, we investigated the oxygen, carbon, and 53Mn-53Cr systematics of carbonate and magnetite in two Ryugu particles. We find that the fluid was initially between 0−20 °C and enriched in 13C, and 17O and 18O, and subsequently evolved towards lighter carbon and oxygen isotopic compositions as alteration proceeded. Carbonate ages show that this fluid-rock interaction took place within the first ~1.8 million years of solar system history, requiring early accretion either in a planetesimal less than ~20 km in diameter or within a larger body which was disrupted and reassembled.

Astromaterials↗