^1,4Anna-Irene Landi, ²Michael Gaft, ³Cristian Carli, ³Fabrizio Capaccioni, ⁴Giovanni Pratesi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116725]
¹Dipartimento di Fisica, Università degli Studi di Trento, Via Sommarive, 14, 38123 Trento, Italy.
²Ariel University, Kiryat Hamada, Ariel 40700, Israel.
³INAF-IAPS, Area della Ricerca Tor Vergata, Via del Fosso del Cavaliere, 100, 00133 Roma, Italy
⁴Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira, 4, 50121 Firenze, Italy
Copyright Elsevier

Rantila aubrite fell in Rantila, Gujarat, India, in August 2022. This study aims to investigate the mineralogy and mineral-chemistry of three fragments of this meteorite and correlate them reflectance spectroscopy in the visible and near-infrared spectral range (VNIR) and Laser-Induced Time-Resolved Luminescence (LITRL). Aubrites’ very low Fe2+ content prevents luminescence quenching under UV light exposure, allowing these meteorites to exhibit well-defined luminescence. The investigated samples have different appearances. One consists of a light-coloured portion primarily composed of FeO-free enstatite, along with forsterite, diopside, plagioclase, minor sulphides (troilite, alabandite, daubréelite, and (Fe,Ca,Mn,Mg)S), and kamacite. The second sample is composed mainly of the same light-coloured portion and hosts a dark forsterite clast. The third sample is mainly made of dark glass. Minor terrestrial weathering is observed, with the detection of sporadic iron oxides/hydroxides. The chemical composition of the detected phases indicates highly reducing conditions during the formation, as expected for an aubrite. The mineral chemistry is similar between the different fragments in terms of major elements concentrations, some differences are observed for minor elements. Luminescence spectra indicate Cr3+ and Mn2+ as activators in diopside and forsterite, respectively, for two of the three samples. Ce3+ is the activator in the third sample, which lacks forsterite and has lower Cr2O3 contents in diopside compared to the other two samples. Therefore, the differences in mineral chemistry observed through electron microprobe analysis (EPMA) are further emphasized by luminescence data. Investigating the luminescence behaviour could provide a valuable contribution to the mineralogical-petrological study of these materials. VNIR reflectance spectra are consistent with low Fesingle bondCa pyroxene and forsterite. The main absorption typical of mafic minerals (~0.9 μm) is deeper than what has previously been observed in aubrites: this can be related to the slightly higher FeO concentrations, which, despite being very low (<0.4 wt%), still contribute to the absorption. Absorption features at ~1.4 μm and ~ 1.9 μm are consistent with low terrestrial weathering presence. Increasing the knowledge of the correlation between spectral properties and mineralogy/mineral chemistry on highly reduced meteorites will be useful for future investigation of Mercury with the ESA’s BepiColombo mission, specifically for the interpretation of the data expected from the Spectrometer and Imagers for MPO BepiColombo Integrated Observatory SYStem (SIMBIO-SYS)/Visible and near Infrared Hyperspectral Imager (VIHI) and Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) instruments.

¹Tetsushi Sakurai, ²Takuya Ishizaki, ¹Akiko M. Nakamura
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116729]
¹Department of Planetology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe-city, Hyogo 657-8501, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara-city, Kanagawa 252-5210, Japan
Copyright Elsevier

Planetesimals underwent consolidation processes in the early solar system, which altered their thermal and mechanical properties. Sintering—a process that forms solid necks between particles—is considered one such process in planetesimals, influencing their filling factor, or porosity, as well as their thermal and mechanical properties.
In this study, to better constrain and understand the thermal and mechanical properties of planetesimals that evolved from initially powdery or granular bodies, as well as those of boulders on small bodies, which are considered remnant planetesimals, we prepared porous sintered samples consisting of glass particles with filling factors ranging from 0.35 to 0.75, corresponding to porosities of 65 % to 25 %. We then measured their thermal diffusivity, elastic wave velocity, and flexural strength, and derived empirical relationships for the normalized values—scaled by those at a filling factor of 1—as functions of filling factor or porosity. The normalized thermal diffusivities and elastic wave velocities of the sintered glass materials in this study showed similar dependencies on the filling factor. Moreover, the upper limits of the normalized elastic wave velocities were consistent with those of snow at corresponding filling factors, suggesting that these upper limits may be independent of the matrix material.
The derived empirical relationships apply to materials with porosities higher than those of meteorites. We estimated the porosity of a low-thermal-inertia boulder on the surface of asteroid Ryugu based on its thermal inertia, assuming no influence from internal cracks. The result suggests that the boulder’s porosity may be higher than values previously reported, and should be regarded as one of the possible porosity estimates.