Extended Silicic Volcanism in the Gruithuisen Region—Revisiting the Composition and Thermophysical Properties of Gruithuisen Domes on the Moon

The formation mechanisms, extent, and compositions of red spots on the lunar surface have intrigued the lunar community for decades. By identifying a new dome and another silicic crater in the highlands nearby, we find that the silicic volcanism in the Gruithuisen region extends beyond the three major domes. Our observations indicate that the Gruithuisen domes have low iron and titanium contents. They are enveloped by ejecta from surrounding regions and host silica-rich material excavated by the young craters consistent with previous work. Our boulder maps of the Gamma dome display a high boulder count and indicate that the Diviner rock abundance maps are only sensitive to boulders larger than ∼2 m. The H-parameter values are sensitive to presence of rocks and may be a better indicator of rocks at submeter scales. The Delta dome has gentle slopes, lower rock abundance, and one young crater, and it could serve as a safe and scientifically valuable site for landing and exploration of the domes and nearby region. The dome also displays anomalously high H-parameter in the same region as the crater, indicating the potential presence of pyroclastic materials. We observe up to 200 ppm of OH/H2O on the domes and nearby mare despite the presence of a weak magnetic field to the south of Delta dome, further supporting the potential presence of pyroclastics in the region. This study could potentially aid in logistical and scientific decisions of the future NASA missions in the region

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

Mid-infrared reflectance spectra and optical constants of six iron oxide/oxyhydroxide phases

We have determined the real and imaginary indices of refraction (n and k) for six iron oxide/oxyhydroxide phases—magnetite, maghemite, goethite, lepidocrocite, akaganéite, and ferrihydrite. A single crystal of magnetite was used to derive bulk n and k values from 100–2000 cm^(−1) (5–100 μm). Synthetic nanocrystalline samples of maghemite, goethite, lepidocrocite, akaganéite, and ferrihydrite were pressed into compact pellets used to determine bulk n and k values from 100–1200 cm^(−1) (8.33–100 μm). All values of n and k (the optical constants) were determined from specular reflectance spectra acquired at 2 cm^(−1) spectral sampling using classical Lorentz–Lorenz dispersion theory. In this paper, we present the optical constants of all six minerals and the oscillator parameters with which they were modeled. Use of these optical constants could aid in radiative transfer models of terrestrial dust as well as Mars, the Moon, and airless bodies in the Solar System

Nano-FTIR spectroscopic identification of prebiotic carbonyl compounds in Dominion Range 08006 carbonaceous chondrite

Meteorites contain organic matter that may have contributed to the origin of life on Earth. Carbonyl compounds such as aldehydes and carboxylic acids, which occur in meteorites, may be precursors of biologically necessary organic materials in the solar system. Therefore, such organic matter is of astrobiological importance and their detection and characterization can contribute to the understanding of the early solar system as well as the origin of life. Most organic matter is typically sub-micrometer in size, and organic nanoglobules are even smaller (50-300 nm). Novel analytical techniques with nanoscale spatial resolution are required to detect and characterize organic matter within extraterrestrial materials. Most techniques require powdered samples, consume the material, and lose petrographic context of organics. Here, we report the detection of nanoglobular aldehyde and carboxylic acids in a highly primitive carbonaceous chondrite (DOM 08006) with similar to 20 nm spatial resolution using nano-FTIR spectroscopy. Such organic matter is found within the matrix of DOM 08006 and is typically 50-300 nm in size. We also show petrographic context and nanoscale morphologic/topographic features of the organic matter. Our results indicate that prebiotic carbonyl nanoglobules can form in a less aqueous and relatively elevated temperature-environment (220-230 degrees C) in a carbonaceous parent body.RISE2 node of NASA's Solar System Exploration Research Virtual Institute (SSERVI)We thank the associate editor and the reviewers for their constructive comments, which significantly improved this manuscript. We thank NASA-JSC for providing the meteorite samples. This work was also supported in part by the RISE2 node of NASA's Solar System Exploration Research Virtual Institute (SSERVI; PI: T.D. Glotch).WOS:0006873225000792-s2.0-85107118526PubMed: 3407903

Thermal metamorphic history of Antarctic CV3 and CO3 chondrites inferred from the first- and second-order Raman peaks of polyaromatic organic carbon

Parent body thermal metamorphism is an important process that alters the structure of organic matter in the parent asteroid of meteorites. Increasing and progressing thermal metamorphism results in carbonization and graphitization of carbonaceous matter in the parent body. Such modifications in the carbon structures can be studied by Raman microspectroscopy, thanks to its high sensitivity to structure and bonding within carbonaceous molecules. We have characterized polyaromatic carbonaceous matter in a total of 24 Antarctic CV3 and CO3 chondrites using micro-Raman imaging spectroscopy in an effort to better understand parent body thermal metamorphism and assess its effects on the carbon structures. Raman spectral parameters of the first-order carbon peaks (D and G) were extracted from at least 200 spectra for each meteorite and were compared to deduce relationships that yield information regarding the thermal metamorphism conditions. We also show, for the first time, spectral trends and relations of the second-order carbon peaks (2D and D+G) within the 2500-3200 cm(-1) with thermal metamorphic history. The second-order peaks appear to contain information that is lacking in the first-order peaks. Based on the second-order carbon peak parameters, we tentatively classify four CV3 chondrites into subtypes, and reclassify another. Peak metamorphic temperatures of the investigated meteorites have been estimated based on the width of the D band as well as the calculated Raman spectral curvature. Estimated temperatures appear to correlate well with the assigned petrologic types. We have calculated higher peak metamorphic temperatures for the CV3 chondrites than for the considered CO3 chondrites and further showed that the peak metamorphic temperatures of CV3(oxA) chondrites are higher than those of CV3(oxB), indicating possibly different metamorphic conditions for the two oxidized subtypes. We observe that there is a relatively larger temperature increase going from CO3.2 to CO3.4 (150 degrees C increase) compared to CO3.4-CO3.6 (20 degrees C), which may indicate that the graphitization and structural ordering of carbon reach a critical temperature regime around petrologic type CO3.3.Ministry of Industry and Technology of Turkey; TUBITAK MAM Polar Research InstituteThis work is funded in part by the RISE2 node of NASA's Solar System Exploration Research Virtual Institute (SSERVI; PI: T.D. Glotch) M.Y. acknowledges the support by the Ministry of Industry and Technology of Turkey as well as TUBITAK MAM Polar Research Institute. The data presented here will be made publicly available at Turkish Spectral Database upon publication (http://tsd.klu.edu.tr).WOS:0006460250000022-s2.0-8509680017

NANOSCALE INFRARED INVESTIGATION OF ORGANICS IN CARBONACEOUS CHONDRITES

[Abstract Not Available]WOS:00068401430029

Nanoscale Infrared Characterization of Dark Clasts and Fine-Grained Rims in CM2 Chondrites: Aguas Zarcas and Jbilet Winselwan

Carbonaceous chondrites are among the most primitive meteorites that escaped extreme temperatures and melting in their parent bodies and, as such, offer valuable records of the parent body origins, formation, and evolution. The presence of organic molecules and carbonaceous phases make CM chondrites invaluable as they may have contributed prebiotic material to early Earth. Fine-grained rims (FGRs) and organic-rich dark clasts are particularly interesting features, the origin, formation, and evolution of which are not fully understood. In this study, we aimed to characterize several FGRs and dark clasts in two CM2 chondrites, Aguas Zarcas and Jbilet Winselwan, using backscattered electron images, confocal micro-Raman spectroscopy, and nanoscale near-field infrared imaging and spectroscopy. The nano-FTIR spectra show that the dark clasts and FGRs are chemically heterogeneous at a submicron scale and those of Aguas Zarcas are composed of organics (such as aliphatics, aromatics, and carbonyls) as well as alteration phases (such as phyllosilicates, carbonates, and sulfates). The FGRs are compositionally almost identical and exhibit heterogeneous alteration as well as a lack of fragmentation. The thicknesses of FGRs positively correlate with the enclosed chondrule diameter regardless of the chondrule type. The samples appeared to have experienced minimal brecciation after the chondrules were surrounded by the FGRs. These observations suggest nebular origin for the FGRs. The presence of organics embedded within these FGRs may further indicate that they may have formed in the solar nebula as well. In comparison, Jbilet Winselwan contains relatively less organics and exhibits more thermally metamorphosed mineralogy and matrix textures. These features could be the result of short-duration heating, such as impact heating, which also likely caused shock and dehydration/decomposition of the hydrated phases. © 2021 American Chemical Society.DPT2006K12-827; 119N207, 120Y115This work was supported by TUBITAK (PI: M.Y., project numbers 119N207 and 120Y115) and RISE2 node of NASA-SSERVI (PI: T.D.G.). M.K. acknowledges the TARLA project, founded by the Ministry of Development in Turkey (project code: DPT2006K12-827).2-s2.0-8511999555

Carbonaceous matter in the Sariçiçek meteorite

As of today, the Sariçiçek (SC) meteorite is the newest howardite and the only confirmed fall among the 17 known howardites. In this study, we present isotopic, infrared, and Raman data on three distinct pieces of the SC meteorite. Our oxygen isotopic measurements show that Δ17O values of the pieces are close to each other, and are in good agreement with other howardites, eucrites, and diogenites. The carbon isotopic measurements, which were conducted by combusting terrestrial contamination selectively at temperatures lower than 500–600 °C, show the presence of indigenous carbon in the SC specimens. The matrix of these specimens, investigated via infrared microspectroscopy, appears to be dominated by clinopyroxene/orthopyroxene, forsterite, and fayalite, with minor contributions from ilmenite, plagioclase, and enstatite. Carbon‐rich regions were mapped and studied via Raman imaging microspectroscopy, which reveals that both amorphous and graphitic carbon exist in these samples. Synchrotron‐based infrared microspectroscopy data show the presence of very little aliphatic and aromatic hydrocarbons. The SC meteorite is suggested to be originating from the Antonia impact crater in the Rheasilvia impact basin on 4 Vesta (Unsalan et al. 2019). If this is in fact the case, then the carbon phases present in the SC samples might provide clues regarding the impactor material (e.g., carbonaceous chondrites)

Mid-infrared (5–100 μm) reflectance spectra and optical constants of ten phyllosilicate minerals

We have derived the real and imaginary indices of refraction for 10 phyllosilicate minerals—montmorillonite, beidellite, nontronite, hectorite, saponite, illite, illite–smectite (60/40 interlayered) kaolinite, halloysite, and serpentine—from 100–2000 cm^(−1) (5–100 μm) at 2 cm^(−1) spectral sampling using classical Lorentz–Lorenz dispersion theory. We present the real and imaginary indices and the oscillator parameters with which they were modeled. Use of these optical constants will aid in the modeling of thermal infrared spectra of planets, asteroids, interplanetary and interstellar dust, and protoplanetary disks around nearby stars