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Most carbonaceous (C) chondrites are classified into eight major groups: CI, CM, CO, CV, CK, CR, CH, and CB. However, some are ungrouped. We studied two such chondrites, Asuka (A)‐9003 and A 09535. The abundance of chondrules and matrix and chondrule sizes in these meteorites are similar to those in ordinary chondrites and unlike any known carbonaceous chondrite group. In contrast, they contain 4–6 vol% of refractory inclusions and have oxygen isotopic compositions within the range of CO and CV chondrites. Therefore, A‐9003 and A 09535 are classified as C chondrites. Petrologic subtypes of A‐9003 and A 09535 are 3.2. All these features closely resemble those of another ungrouped chondrite, Yamato (Y)‐82094, and differ from those of any C chondrites reported by now. A‐9003, A 09535, and Y‐82094 likely represent a new type of C chondrite. We provisionally call them CA chondrite after Asuka in Antarctica. Our study suggests a wider range of formation conditions for C chondrites than currently recorded by the major C chondrite groups. [ABSTRACT FROM AUTHOR]

Introduction: The Hayabusa2 mission returned approximately 5.4 g of highly aqueously-altered material resembling the CI (Ivuna-type) chondrites from the C-type asteroid Ryugu [1,2]. In order to understand the timing and duration of aqueous alteration which occurred on the Ryugu parent body, we measured the 53Mn-53Cr (t1/2 = 3.7 Myr) ages of carbonates in two Ryugu particles, A0037 and C0009. We then use these carbonate formation ages to constrain the accretion time and size of Ryugu's parent body. Methods: The 55Mn+/52Cr+ and 53Cr+/52Cr+ ratios of Ca-carbonate, dolomite, and breunnerite from particles A0037 and C0009 were measured using the CAMECA ims-1290 ion microprobe at UCLA. Analyses were performed using a 1 nA 16O3 - beam generated by an Oregon Physics Hyperion-II plasma ion source [3]. An MRP of ~5500 was used to separate 52Cr+ from 28Si24Mg+ and 53Cr+ from 52CrH+. Analysis spots were presputtered using an 8 × 8 or a 4 × 4 μm raster to remove surface Cr contamination before reducing the raster to 5 × 5 or 2 × 2 μm for analysis. The effective spot size was approximately 8 × 10 μm². The instrumental mass fractionation for the Cr isotopic ratio was corrected by comparison to repeated measurements of a terrestrial dolomite with trace amounts of Cr. The relative sensitivity factor (RSF) between Mn and Cr is defined as RSF = (55Mn/52Cr)True / (55Mn / 52Cr)SIMS and was determined using a combination of San Carlos Olivine and ion-implanted calcite, dolomite, and breunnerite standards. Results: The inferred initial 53Mn/55Mn ratios for Ryugu carbonates are 6.8 ± 0.5 × 10-6 (MSWD = 0.7) for A0037 dolomite and 6.1 ± 0.9 × 10-6 (MSWD = 0.3) for C0009 dolomite, Ca-carbonate, and breunnerite (all errors 2SE). When these ratios are calibrated relative to the initial 53Mn/55Mn of the D'Orbigny angrite [4], an 'anchor' sample with a well-defined Pb-Pb crystallization age [5,6], we calculate that A0037 and C0009 carbonates formed at 4566.9 ± 0.4 Ma and 4566.3 ± 0.4 Ma, respectively--that is, within the first 1.4 Myr after the CAI 'time zero' age of 4567.3 Ma [7]. This is significantly older than inferred from previous studies of CI chondrites [8,9]. Discussion: These old carbonate formation ages stand in contrast to ages obtained from carbonate in CI chondrites, most of which were thought to have formed 4-6 Myr after CAI formation [8,9]. We attribute this difference to our use of matrix-matched standards for the dolomite and breunnerite analyses. Had we corrected measured Mn+/Cr+ using a relative sensitivity factor derived only from analyses of calcite, we would have obtained ages of 3.0 Myr and 3.5 Myr after CAI formation for A0037 and C0009 carbonate respectively. Size and timing of accretion of the Ryugu parent body. Formation of carbonate within the first 1.4 Myr after CAI suggests a significantly different formation scenario than the large (>50 km) parent bodies accreting ~3-3.5 Myr after CAI which had been previously inferred for the parent bodies of CI chondrites [8,9]. Early accreted parent bodies would have had a high abundance of 26Al to drive water loss or even silicate melting and chemical differentiation if they cannot effectively conduct heat away by radiation. By modeling parent bodies accreting as mixtures of 50% chondritic material and 50% water ice, we find that parent bodies accreting before 1.4 Myr must be smaller than ~17 km in diameter for the internal temperature to remain below 400 K and avoid water loss. Alternatively, Ryugu material could have been formed in a larger progenitor body which was disrupted by impact before reaching peak temperatures. This multi-stage scenario is supported by petrographic and shock characteristics observed in Ryugu particles [10,11]. [ABSTRACT FROM AUTHOR]

Introduction: Between June 2018 and November 2019, the JAXA Hayabusa2 spacecraft made detailed observations and measurements of the C-type asteroid 162173 Ryugu. Two samples were collected and returned to Earth on 6th December 2020: a surface sample stored in Chamber A of the return capsule and a sub-surface sample in Chamber C. Near-IR orbital spectroscopic data indicated that Ryugu comprised material "similar to thermally and/or shockmetamorphosed carbonaceous chondrite meteorites" [1], with a possible match to the CY (Yamato-type) chondrites [2]. In contrast, initial studies at the JAXA ISAS facility suggested that the samples were "most similar to CI chondrites" [3]. Resolving these contradictory classifications requires detailed sample analysis studies. Here we present high precision O-isotopic results undertaken as part of Phase2 Kochi curation studies [4]. Ryugu particles show evidence of pervasive asteroidal aqueous alteration [4, 5], with only minor preservation of relict primary silicates [6]. Methods: Seven sub-samples from four of the particles allocated to Kochi curation were analysed by laser fluorination [7]. Three particles were from Chamber C (C0014,21; C0068,21; C0087,2) and one from Chamber A (A0098, 2). Orgueil (CI) (n=7) and Y-82162 (CY) (n=7) were analysed for comparison purposes. Sample transport, loading and analysis techniques employed ensured that the particles were never exposed to atmospheric contamination [8]. All Ryugu samples were run in "single shot" mode [9]. In most cases the amount of O2 gas liberated was less than 140 μg, the approximate limit for bellows analysis on the MAT 253. In these cases analysis was undertaken using the MAT 253 cryogenic microvolume. Δ17O values were calculated as Δ17O = δ17O-0.52δ18O. Results: The weighted average of the Ryugu analyses, both in terms of Δ17O and δ18O, is close to that for Orgueil (CI), but plots away from that of the CY chondrite Y-82162. This data supports the proposed relationship between Ryugu and the CI chondrites [3-5]. Individual Ryugu analyses show a large range in δ18O values, from 11.46‰ to 19.30‰ (blank corrected values). This large range reflects intrinsic isotopic heterogeneity at the sampling scale involved, with detailed mineralogical studies [4, 5] indicating a significant level of heterogeneity within individual Ryugu particles. In addition, SIMS analysis reveals that Ryugu mineral phases are isotopically heterogeneous, with magnetite and Ca-carbonate differing by more than 30‰ [10]. In contrast, analyses for Orgueil and Y-82162 were drawn from homogenized powders. Calculations, using Ryugu modal data [4], yield bulk δ18O values close to the range determined in this study. There is a small resolvable difference between the average Δ17O composition of the Ryugu particles and Orgueil, (0.66 ± 0.09‰ and 0.0.58 ± 0.09‰ respectively (2SD weighted)). Calculation indicates that this difference reflects the terrestrial contamination of Orgueil [8]. Discussion and conclusions: Despite the close O-isotope similarities between Ryugu particles and Orgueil, suggesting a genetic relationship between them, our data reveal higher Δ17O values for Ryugu particles compared to Orgueil. This difference likely reflects terrestrial contamination of Orgueil since its fall in 1864 [11]. Weathering in the terrestrial environment would pull the bulk analysis closer to the TFL. This conclusion is consistent with evidence that interlayer water in Orgueil is of terrestrial origin [12], and that Orgueil contains ferrihydrite and sulphate [13], whereas Ryugu particles do not [4, 5]. While Ryugu particles are the most uncontaminated CI-related material we have [8], they are not pristine and have been modified by a variety of processes in the regolith [14]. The evidence from Ryugu suggests that care needs to be taken when using CI meteorite data as Solar System proxy values e.g. [15]. [ABSTRACT FROM AUTHOR]

Magnesium phosphate grains, minor accessory minerals found on the primitive meteorite Yamato 980115 (Y 980115), were investigated by Raman microspectroscopy. All magnesium phosphate grains found in the present study can be assigned to farringtonite, dehydrated magnesium phosphate Mg 3 (PO 4 ) 2 -I. Since the Mg 3 (PO 4 ) 2 -I is generally formed via the irreversible thermal transition from the polymorphs of Mg 3 (PO 4 ) 2 -II and -III at above 750-800 degree Celsius, we can infer that the parent body of the Y 980115 meteorites experienced thermal alteration with such a high temperature. This result is in good accordance with the previous studies and the proposals on the alteration history of Y 980115 by the electron-beam microscope and X-ray diffraction analyses. Furthermore, the hydrated form of the magnesium phosphates of Mg 3 (PO 4 ) 2 ·4H 2 O, Mg 3 (PO 4 ) 2 ·8H 2 O, and Mg 3 (PO 4 ) 2 ·22H 2 O was not found in the present research, also suggesting that the extensive vaporization of the hydrated water molecules with magnesium phosphate occurred by such high-temperature thermal alteration. Since Y 980115 has been historically categorized to heavily aqueously altered CI (Ivuna-type) carbonaceous chondrites but has distinct characteristic to CI meteorites, the present result would provide further evidence to the complexed alteration history of the parent body of Y 980115 meteorite., Competing Interests: Declarations. Conflict of interest: The authors have no competing interests to declare that are relevant to the content of this article., (© 2025. The Author(s).)

Silica polymorphs occur under various pressures and temperature conditions, and their characteristics can be used to better understand the complex metamorphic history of planetary materials. Here, we conducted isothermal heating experiments of silica polymorphs in basaltic eucrites to assess their formation and stability. We revealed that each silica polymorph exhibits different metamorphic responses: (1) Quartz recrystallizes into cristobalite when heated at ≥ 1040 °C. (2) Monoclinic (MC) tridymite recrystallizes into no other polymorphs when heated at ≤ 1070 °C. (3) Silica glass recrystallizes into quartz when heated at 900-1010 °C, and recrystallize into cristobalite when heated at ≥ 1040 °C. These results suggest that MC tridymite in eucrites does not recrystallize into other polymorphs during the reheating events, nor does it recrystallize from other silica phases below the solidus temperature of eucrite (~ 1060 °C). Additionally, we found that pseudo-orthorhombic (PO) tridymite crystallizes from quenched melts in the samples heated at ≥ 1070 °C. Previously, cristobalite has been considered as the initial silica phase, which crystallizes from eucritic magma. Our findings suggest that the first crystallizing silica minerals may not always be cristobalite. These require a reconsideration of the formation process of silica minerals in eucrites., (© 2024. The Author(s).)

Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P1) noble gases are present in Ryugu samples with concentrations higher than those observed in CIs, suggesting the former to be more primitive compared to the latter. Here we present results of analyses of three fine-grained samples from Ryugu, in one of which Xe concentration is an order of magnitude higher than determined so far in other samples from Ryugu. Isotopically, this Xe resembles P1, but with a much stronger isotopic fractionation relative to solar wind and significantly lower 36 Ar/ 132 Xe ratio than in P1. This previously unknown primordial noble gas component (here termed P7) provides clues to constrain how the solar composition was fractionated to form the planetary components., (© 2024. Crown.)

A sample holder for a suite of synchrotron radiation measurements on extraterrestrial materials, which are fragile and irregularly shaped, was developed using carbon nanotubes and polyimide. The holder enables investigation of such samples with multiple analytical instruments, which means that we can reduce the number of sample transfers between holders. The holder developed in our study also enables investigation of such samples without exposure to the terrestrial atmosphere, which contains abundant contaminants, such as water vapor and organic substances. The stability of the samples in the holder during the measurements and disturbance of the analysis result by the holder were evaluated, which showed that sample drift motion and image disturbance due to x-ray attenuation and scattering of the holder materials are insignificant.

A 38-year-old hemophiliac, who had been infected with HIV by the administration of blood products and had been diagnosed as AIDS by the onset of Pneumocystis carinii pneumonia, was admitted to our hospital with the complaints of headache and vomiting. After he was diagnosed as cryptococcal meningitis using the microscopy, cryptococcal antigen detection and culture of cerebrospinal fluid, treatment with amphotericin-B and fluconazole was started. As there was no clinical improvement, spinal drainage was performed and acetazolamide administered in order to reduce the intracranial pressure. Treatment was changed from AMPH-B and FLCZ to a combined therapy of AMPH-B and itraconazole. As his clinical features showed improvement, he was discharged home on a maintenance dose of ITCZ and acetazolamide after having been hospitalized for three months. This case-report may be of use in the management of cryptococcal meningitis in patients with AIDS.