¹Yasuhiro Oba et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.06.040]
¹Institute of Low Temperature Science (ILTS), Hokkaido University, N19W8, Kita-ku, Sapporo, Hokkaido 060-0819, Japan
Copyright Elsevier

Carbonaceous meteorites preserve organic records of early Solar System chemistry, yet nucleobase inventories remain difficult to interpret owing to potential terrestrial contamination and parent–body processing effects. Here we report high–resolution liquid chromatography/Orbitrap mass spectrometry analyses of purine and pyrimidine bases in six Antarctic carbonaceous meteorites (CM: Y–791198, A–12236, Y–793321, B–7904; CR: A–881828, Y–002540) using rigorously controlled extractions (hot water and 20% HCl treatments) performed in ISO–class clean environments, together with Antarctic ice as an environmental blank. All five canonical nucleobases were identified in Y–791198, A–12236, and A–881828; subsets were found in Y–793321 and Y–002540; and none were detected in B–7904 or in the ice meltwater/hydrolysate. These patterns, coupled with the thermal metamorphic history of B–7904, indicate no detectable incorporation of nucleobases from Antarctic ice during ∼ 105–year residence. Total pyrimidines correlate positively with NH3 across Antarctic meteorites and previously reported extraterrestrial samples, whereas purines do not, implicating NH3-facilitated pyrimidine formation and the involvement of additional precursors (e.g., cyanides) in purine synthesis. Cytosine is systematically depleted relative to other canonical bases, likely reflecting its low–temperature hydrolysis to uracil; leaching losses appear negligible as highly water-soluble species (e.g., hydroxypyrimidines and NH3) are retained within the meteorites. Our results establish Antarctic meteorites as some of the least contaminated materials for constraining nucleobase distributions and underscore the need for direct cyanide measurements to resolve purine formation pathways.

¹Yuki Masuda, ²Yoshiaki Shiraishi, ²Tetsuya Yokoyama, ³Tsuyoshi Iizuka, ¹Martin Schiller, ¹Martin Bizzarro
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.07.004]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
²Department of Earth and Planetary Sciences, Institute of Science Tokyo, Meguro, Tokyo 152-8551, Japan
³Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
Copyright Elsevier

Chondrules are high-temperature products formed in the protoplanetary disk and are ubiquitous components of undifferentiated extraterrestrial materials. Nucleosynthetic isotope anomalies preserved in chondrules provide a valuable record of isotopic evolution of solids from presolar dust to the accretion of planets. Among various types of chondrules, Al-rich chondrules (ARCs) possess intermediate isotopic and chemical compositions between calcium-aluminum-rich inclusions (CAIs) and ferromagnesian chondrules (FMCs), providing insights into mixing processes of various materials formed in different regions and/or at different times in the protoplanetary disk. This study performed analyses of the abundances of 54 elements and multi-elemental isotopic compositions of Ca-Ti-Cr-Sr on fourteen ARCs extracted from four Vigarano-type chondrites (CVs). Their element abundance patterns demonstrate enrichments reaching up to 10 times of Ivuna-type carbonaceous chondrites (CIs) in refractory elements and depletions down to < 0.05 × CI in volatile elements. Eight ARCs show highly fractionated rare-earth-elements (REEs) signatures, while six ARCs display flat REE patterns. These features suggest that CV ARCs have recycled refractory inclusions, including fine-grained CAIs (FG-CAIs) and other REE-unfractionated types, in addition to less-refractory components with chondritic or matrix-like compositions similar to those contributing to FMCs. The Ca, Ti, and Sr isotopic compositions of the ARCs exhibit variations ranging from those of non-carbonaceous chondrite (NC) components to coarse-grained CAIs (CG-CAIs) and FG-CAIs. The observed isotopic compositions are not consistent with a simple mixture of NC with a single type of refractory inclusion, suggesting that they contain various types of refractory materials. The Cr isotopic compositions of CV ARCs are intermediate between those of NCs and CIs. The observed isotopic variation indicates that components of NC, CI, and refractory inclusions coexisted in the CV chondrule-forming region. This is in contrast to NC chondrule-forming regions, which do not exhibit isotopic anomalies characteristic of refractory inclusions. The significant difference in the degree of CAI signatures between OC ARCs and CV ARCs suggests that CAIs were trapped between the accretion regions of NC and CC parent bodies, leading to an isotopic dichotomy based on the presence or absence of isotopically anomalous CAIs. Meanwhile, fine dust grains with NC or CI isotopic compositions, which are smaller in size than CAIs, were distributed extensively in NC and CC accretion regions, resulting in continuous variations in chondrule isotopic composition.