Discovery of fossil asteroidal ice in primitive meteorite Acfer 094

Abstract

Discovery of fossil asteroidal ice in a meteorite provides new insight into asteroid formation in the early Solar System.

Discovery of primitive CO 2 -bearing fluid in an aqueously altered carbonaceous chondrite

“…S1). The samples were imaged using SR-XCT to obtain their three-dimensional (3D) images with absorption and phase-shift contrasts using two different methods: dual-energy tomography (DET) ( 7 ) and scanning-imaging x-ray microtomography (SIXM) ( 8 ) with ~70 and 100 nm in voxel size, respectively ( 3 ). A large number of inclusions in the interior of calcite grains were recognized in 3D ( Fig.…”

“…As the LAC and RID values obtained by the reconstruction are slightly smaller than the real values, we corrected the LAC and RID values by calibration using standard materials as performed in ( 3 ). We searched for inclusions in the CT images by both DET and SIXM, and their locations in the samples in 3D were recognized using an open source image processing package “Fiji-ImageJ.” Inclusions in calcite grains were digitally extracted by binarization of 3D-CT images, and their bird’s-eye views were made ( Fig.…”

“…Minerals and ice were accreted together outside the SL to form planetesimals. Aqueous alteration by reaction of melted ice with anhydrous minerals occurred and was recorded in some primitive meteorites called carbonaceous chondrites (CCs) [e.g., ( 3 )]. Water is mostly present as hydroxyl and/or H 2 O molecules of hydrous minerals.…”

Thermal metamorphism of CM chondrites: A dehydroxylation‐based peak‐temperature thermometer and implications for sample return from asteroids Ryugu and Bennu

“…Aqueous alteration in CM chondrites was driven by mild heating that caused melting of water ice physically intermixed with silicate matter. The former presence of water ice has long been inferred by many studies of CM chondrites and was recently convincingly demonstrated by Matsumoto et al (2019). Such CMs are commonly referred to as aqueously altered.…”

A preparation sequence for multi‐analysis of µm‐sized extraterrestrial and geological samples

“…In this context, it is necessary to perform multiple complementary analyses on micrometer-sized samples, from the least destructive to the most destructive methods to maximize scientific outcomes and minimize sample loss and contamination. Multi-analytical sequences were successfully used in the recent past to analyze (1) samples from comet Wild 2 and asteroid Itokawa returned by the Stardust and Hayabusa space missions, respectively (e.g., Zolensky et al 2008;Nakamura et al 2011); and (2) very small and unique meteorites (e.g., Acfer 094, Matsumoto et al 2019). Those sequences either consisted of successive analyses on the same thin section such as XANES (X-ray absorption near edge structure), TEM, and finally NanoSIMS which, in the end, consumed integrally the section (e.g., Stadermann et al 2005;Zolensky et al 2008;De Gregorio et al 2011), or consisted of 3-D-XCT (X-ray computed tomography), -XRD (X-ray diffraction), or -XRF (X-ray fluorescence) analyses of a grain subsequently sliced in several sections, which were analyzed independently by different techniques (e.g., TEM or NanoSIMS, Nakamura et al 2011;Matsumoto et al 2019).…”