Meteoritics & Planetary Science最新文献

C-type asteroids, such as asteroid (162173) Ryugu, may have played a key role in delivering light elements to early Earth. Nitrogen (N)-bearing molecules have been chemically identified in some Ryugu grains, and based on the faint 3.06 μm absorption band observed by the hyperspectral microscope MicrOmega, NH-bearing compounds seem to be spread at the global scale in the collection. However, the chemical forms of these NH-bearing compounds—whether organic molecules, ammonium (NH₄⁺) salts, NH₄⁺- or NH-organics-bearing phyllosilicates, or other forms—remain to be better understood. In this study, we report the characterization of two Ryugu particles (C0050 and C0052) using infrared spectroscopy at millimeter, micrometer, and nanometer scales, along with NanoSIMS techniques to constrain the nature and origin of NH-bearing components in the Ryugu asteroid. Our findings show that Ryugu's C0052 particle contains rare (~1 vol%), micrometer-sized NH-rich organic compounds with peaks at 1660 cm⁻¹ (mainly due to C=O stretching of the amide I band) and 1550 cm⁻¹ (mainly due to N-H bending vibration mode of the amide II band), indicative of amide-related compounds. In contrast, these compounds are absent in C0050. Notably, N isotopic analysis reveals that these amides in C0052 are depleted in ¹⁵N (δ¹⁵N ≃ −200‰), confirming their indigenous origin, while carbon (C) and hydrogen (H) isotopic compositions are indistinguishable from terrestrial values within errors. The amides detected in C0052 could have formed through hydrothermal alteration from carboxylic acids and amines precursors on Ryugu's parent planetesimal. Alternatively, they could have originated from the irradiation of ¹⁵N-depleted N-bearing ice by ultraviolet light or galactic cosmic rays, either at the surface of the asteroid in the outer Solar System or on the mantle of interstellar dust grains in the interstellar medium. Amides delivered to early Earth by primitive small bodies such as asteroid Ryugu may have contributed to the prebiotic chemistry.

Ultrarefractory Ca,Al-rich inclusions (UR CAIs) in the Sayh al Uhaymir (SaU) 290 CH3 carbonaceous chondrite consist of ultrarefractory Zr,Sc-rich minerals (allendeite, kangite, tazheranite, warkite, and Y-perovskite), grossite, grossmanite, hibonite, melilite, and spinel. Several of them have a core–mantle structure with ultrarefractory minerals concentrated in the core. The unfragmented inclusions are surrounded by layers of spinel, melilite, Sc-diopside, and diopside (not all layers are present around individual inclusions). The UR CAIs have uniform ¹⁶O-rich compositions: Most inclusions have Δ¹⁷O of ~ −23 ± 2‰; a grossite-rich CAI is slightly ¹⁶O-depleted (Δ¹⁷O ~ −17‰). The CAIs are highly enriched in Zr, Hf, Sc, Y, and Ti compared to typical and previously studied UR CAIs from CM2, CO3, and CV3 carbonaceous chondrites. Similar to UR CAIs from other chondrites, the ultrarefractory minerals in SaU 290 CAIs are enriched in heavy rare earth elements (HREEs) relative to more volatile light rare earth elements (LREEs). We conclude that (1) UR CAIs from SaU 290 formed by gas–solid condensation from a gaseous reservoir having variable but mostly solar-like O-isotope composition, most likely near the proto-Sun, and were subsequently transported outward to the accretion region of CH chondrites. (2) The UR oxides and silicates are important carriers of UR REE patterns recorded their possible early fractionation.

The phosphates, apatite and merrillite, are accessory phases in all martian meteorites. Although apatite is commonly used to assess volatile content and speciation in martian meteorites, merrillite is at least twice as abundant in most samples, but poorly understood. Given that shergottites are divided into enriched, intermediate, and depleted subgroups based on bulk differences in light rare earth element (LREE) abundance and isotopic compositions, an understanding of phosphate mineral behavior is essential to deciphering the petrogenetic differences between these groups because they are the main REE-bearing phases. This study examines 10 enriched shergottites, six intermediate shergottites, and four depleted shergottites to investigate systematic variations in phosphate mineralogy and geochemistry. Two nakhlites, a chassignite, ALH 84001, and two pairs of NWA 7034 were also examined to cover all martian meteorite types known to date. Fourteen of the shergottites were previously classified into enriched, intermediate, and depleted subgroups based on bulk rock REE trends and La/Yb ratios. The remaining six shergottites had not been subgrouped during classification. All samples were elementally mapped using the XFM beamline at the Australian Synchrotron, which provided the relative abundance of merrillite, apatite, K-feldspar, and maskelynite within each sample (the same can be achieved with electron microprobe or SEM). We show that it is possible to classify shergottites from a single representative thin section using apatite to merrillite ratios (A¹⁰/M, where A¹⁰ is apatite abundance × 10) and K-feldspar to phosphate ratios (K¹⁰/P, where K¹⁰ is K-feldspar abundance × 10). Enriched shergottites typically have A¹⁰/M of 1.08 to 8.72 and K¹⁰/P of 1.85 to 13.34; intermediate shergottites have A¹⁰/M ranging from 0.5 to 0.96 and K¹⁰/P of 0.36 to 0.94; and depleted shergottites have A¹⁰/M ranging from 0.26 to 0.42 and K¹⁰/P of 0.09 to 0.39. Calculating these ratios thus provides a quick and straightforward method of chemically classifying shergottites that avoids the need to destroy samples for bulk rock REE analysis.

Observations of the lunar exosphere provide valuable insights into dynamic processes affecting the Moon, such as meteoroid bombardment. The Chamberlain model was used to estimate the zenith column density and temperature of Na atoms on August 13/14, 2009 after the maximum of the Perseid meteor shower. The column density and temperature of Na atoms delivered to the lunar exosphere by slowly changing processes during the maximum of the Perseid meteor shower on August 12/13, 2009 are also estimated. Using the Chamberlain model and Monte Carlo simulations, expected ratios of line-of-sight column densities of Na atoms at three observed altitudes on August 12/13, 2009 are obtained. We attribute the heightened intensities of Na emission lines on August 12/13, 2009 to the onset of the third short-term peak in Perseid activity predicted by celestial mechanics. The best agreement between observations and theoretical models is achieved with a theoretical temperature of 3000 K for impact-produced Na atoms. This third peak of Perseids is estimated to have begun between 23:29 and 23:41 UT on August 12, 2009, lasting about 83 min, with a mass flux attributable to the Perseids ranging between 1.6 × 10⁻¹⁶ and 5 × 10⁻¹⁶ g cm⁻² s⁻¹. Additionally, depletion of Li content compared to Na content in the lunar exosphere is detected. We developed a model predicting Perseid meteoroid stream activity on the Moon, comparing it with performed spectral observations of the lunar exosphere. By modeling 25,000 years of comet 109P/Swift–Tuttle's orbits, we identified 175 cometary trails likely to have generated meteoroids near the Earth and the Moon during the Perseid 2009 meteor shower. Our results reveal annual maxima inducing filament trail structures, one of which aligned closely with the observed peak of the increased Na content in the lunar exosphere.

In this study, naturally occurring jarosite samples from Kachchh, India (considered to be Martian analogue) were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Cathodoluminescence–Energy Dispersive X-ray Spectroscopy (CL-EDXS), and Luminescence (thermoluminescence [TL], blue and infrared stimulated luminescence [BSL and IRSL]) methods. FTIR and CL-EDXS studies suggested that jarosite preserves its luminescence characteristics even after annealing the samples to 450°C. This facilitated luminescence studies (TL/BSL/IRSL) to assess the potential use of luminescence-dating methods to establish the chronology of jarosite formation or its transport. Jarosite exhibited TL, BSL, and IRSL signals with varied sensitivities. The TL glow curve of jarosite comprised glow peaks at 100, 150, 300, and 350°C, reproducible over multiple readout cycles. The least bleachable TL glow peak at 350°C is reduced to (1/e)^th of its glow peak intensity (i.e., 36%) with ~100 min of light exposure under a sunlamp. BSL and IRSL optical decay signals comprised three components. These signals exhibited athermal fading of g ~ 6%/decade, but pIRIR signal at 225°C showed a near zero fading. The saturation doses (2D₀) ranged from 700 Gy to 2600 Gy for different signals, which suggests a dating range of ~25 ka using a reported Martian total dose rate of 65 Gy/ka, primarily due to cosmic rays. Multiple TL glow peaks and their widely differing stability also offer promise to discern changes in cosmic ray fluxes over a century to millennia time scale through inverse modeling and laboratory experiments.

NWA 13489 is a meteorite that has been classified as a brachinite. Brachinites are olivine-rich primitive achondrites representing residual products after a variable degree of silicate melt extraction on a barely differentiated, noncarbonaceous asteroid. Nevertheless, NWA 13489 displays petrographic and mineralogical characteristics that are anomalous when compared with other meteorites of that group. The petrography and thermometric data of this sample are compatible with a high metamorphic grade origin. NWA 13489 results in intermediate between type 6 and 7 chondrites, with a thermal regime broadly straddling the FeNi-FeS eutectic and the onset of silicate melting, resembling other meteorites defined as primitive achondrites. Evidence from mineral chemistry, bulk trace element geochemistry, and oxygen and chromium isotope systematics shows a “carbonaceous” composition and, therefore, NWA 13489 is not a brachinite. Rather, together with an ungrouped chondrite (the NWA 11961 C3-ungrouped) and other ungrouped achondrites (the paired NWA 10503/10859), NWA 13489 supports the existence of a distinct carbonaceous-like meteorite grouplet.

Carbonaceous chondrites are meteorites originating from undifferentiated objects of the Solar System, which may retain signatures of primitive matter. Here, we present a comparative study between two CM chondrites Asuka 12236 and Paris, both considered among the most primitive in the carbonaceous chondrite meteorite collection. This work is based on the combination of infrared and Raman micro-spectroscopy, aiming to compare the spectral characteristics of these two peculiar chondrites. We present an average infrared spectrum from the mid to far infrared of Asuka 12236, which has never been reported yet in the literature. Contrary to the average spectrum of Paris, the Asuka 12236 spectrum shows signatures of anhydrous minerals (olivine and or pyroxene) as well as the presence of amorphous phases. These findings are in agreement with the low degree of alteration reported for Asuka 12236. Aromatic primary amines and imines are also detected in Asuka 12236, heterogeneously distributed within the meteorite. In addition, the comparison of the Raman signatures of the two meteorites highlights different carbon structuration and thus thermal histories. Our spectroscopic investigations confirm that Asuka 12236 can be considered more primitive than the Paris carbonaceous chondrite.

Kassab, F., Ferrière, L., & Belhai, D. (2021). Shock-metamorphic microstructures in quartz grains from Albian sandstones from the Tin Bider impact structure, Algeria. Meteoritics and Planetary Science, 56(12), 2273–2280. https://doi.org/10.1111/maps.13766

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We investigated the metal nodules, veins, fine-grained particles of ordinary chondrites (OC) Ash Creek (L6), Ghubara (L5), NWA 6096 (L6), Tsarev (L5), Kunya-Urgench (H5), NWA 1588 (H3.8), Tamdakht (H5) and Timochin (H5) using optical microscopy, SEM, and LA-ICP-MS to determine trace element distributions and understand the origin of these metal components. The metal nodules have a fractionated siderophile element composition differing from OC metal, indicating the elements were distributed during melting. Most nodules and veins are depleted in Cu and the highly refractory siderophile elements (HRSE) Re, Os, Ir, Ru, Pt, and Rh. Nodules and veins are enriched in W, Mo, Ni, Co, Au, As, and Sb compared to OC metal. Kunya-Urgench metal shows progressive depletion of refractory siderophile elements, likely due to in situ fractionation of liquid metal injected into the chondrite host. We modeled crystallization of L and H chondrite metal melts, producing results similar to the observed compositions, supporting the hypothesis that the metal components may have originated from unfractionated melted in situ primary metal of chondrites. Variations between modeled and observed W, Fe, and Ga abundances suggest varying redox conditions during melting or metamorphism. Tsarev nodule has a unique HRSE zoning recording its high-temperature thermal history, with modeled cooling to 1300°C in ~1 year, suggesting crystallization in a thermally insulated environment, possibly under a hot layer of impact ejecta. The low-temperature thermal histories (660–200°C) of investigated meteorites' metal suggest that shock compression and re-heating may have resulted in a subsolidus decomposition/recrystallization of the metal.