^1,2Anna E. Engle, ³Helen E. Maynard-Casely, ^2,1Jennifer Hanley, ³Christopher Baldwin
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117069]
¹Northern Arizona University, Flagstaff, 86011, AZ, USA
²Lowell Observatory, Flagstaff, 86001, AZ, USA
³Australian Centre for Neutron Scattering, ANSTO, Kirrawee DC, 2232, NSW, Australia
Copyright Elsevier

Ethane (CH), propane (CH), and butane (CH₁₀) are present on many outer solar system bodies but our understanding of their solid phase behaviors is still limited. Linear alkanes are known to exhibit multiple solid phases, with at least one of them being a disordered crystalline phase, wherein the molecules remain in a structured placement but have a freedom of rotation about one or multiple axes. Elucidating the properties of these solid phases is critical for understanding the geochemical and geomorphological processes occurring on icy bodies, thus we undertook an investigation of these three simple alkanes at temperatures relevant to the outer solar system via neutron diffraction. We report on extracted thermal expansion properties, observed phase behaviors, and subsequent analysis of their ’loosely packed’ crystal structures through calculations of crystal voids, contact parameters, and fingerprint plots.

^1,2,3Christopher J. Barnes,⁴Aleksander Błasiak,⁵Helge Vinje Birgerheim,⁵Matthias Konrad-Schmolke,⁵Delia Rösel,^3,4Jarosław Majka,⁵Thomas Zack
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70137]
¹Institute of Geological Sciences, Polish Academy of Sciences, Krakow, Poland
²Department of Earth and Environmental Sciences, University of British Columbia Okanagan, Kelowna, British Columbia,Canada
³Department of Earth Sciences, Uppsala University, Uppsala, Sweden
⁴Faculty of Geology, Geophysics & Environmental Protection, AGH University of Krakow, Krakow, Poland
⁵Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
Published by arrangement with John Wiley & Sons

The mineralogy and textures of several fragments from the Ribbeck aubrite were analyzed using a combination of scanning electron microscopy, electron microprobe analysis, μRaman spectroscopy, and laser ablation inductively coupled reaction cell mass spectrometry (LA-ICP-MS/MS). The meteorite fragments are strongly brecciated and show evidence of shock melting. The silicate phases of the fragments predominantly consist of enstatite, albite, and roedderite, with subordinate forsterite, diopside, K-feldspar. Non-silicate phases include kamacite, troilite, oldhamite, and Fe-Ti, Fe-Mn, and Fe-Cr rich sulfides. Tridymite and cristobalite, the latter contained in Si-rich glass, are also present within one enstatite grain. Vesicular fusion crust is apparent in several fragments. The discovery of roedderite is the first reported for the Ribbeck aubrite. In situ Rb/Sr dating combined with chemical analysis of the roedderite was performed via laser ablation ICP-MS/MS using the single-spot dating approach. The average chemistry of 20 roedderite analyses is 68.7 wt% of SiO2, 23.1 wt% of MgO, 4.9 wt% of K2O, and 3.3 wt% of Na2O and is <0.1 wt% of FeO. The total concentrations of Rb and Sr are 282 and <1 μg g−1, respectively. Single-spot Rb/Sr dates from the same 20 analyses yielded a weighted average of 4570 ± 27 Ma, interpreted as the formation age of the Ribbeck aubrite parent body. The result highlights advantages of single-spot Rb/Sr dating compared to short-lived isotopic systems (e.g., 26Al-26Mg, 53Mn-53Cr, and 129I-129Xe), long-lived systems with radiogenic noble gasses (e.g., 40K-40Ar and 238/235U-232Th-4He), and the conventional Rb/Sr isochron approach for meteorite cosmochronology.