Abstract EANA2026-109

Antarctic meteorites are mostly recovered from blue ice fields and are generally considered well preserved compared with hot desert samples [1,2]. Nevertheless, even in ice-field environments with limited soil and liquid-water interaction, terrestrial organic matter from local ecosystems may be transported across ice surfaces and potentially accumulate on meteorites [3]. During the 2024-2025 ULTIMO mission, 115 meteorite candidates and 15 sediment samples were collected from the Belgica Mountains, Eastern Antarctica. In this study, we evaluate terrestrial contamination and biological organic inputs in three meteorites and ten nearby sediment samples by comparing lipid molecular distributions and 16S rRNA gene sequencing data.

The three ordinary chondrites were collected from different blue ice fields in the Belgica Mountains without direct human contact and were curated under sterile conditions at the Royal Belgian Institute of Natural Sciences (RBINS) following their arrival frozen from Antarctica. Sediments were collected from sedimentary traps, moraines, and glacial valleys. Meteorite characterization was performed by SEM-EDS at RBINS. Lipid distributions in meteorites and sediments were analyzed by GC-MS at the Centro de Astrobiología. Microbial communities were characterized by 16S rRNA gene sequencing using the E.Z.N.A. Soil DNA Kit at the University of Liège.

Petrographic observations reveal chondritic textures in all three meteorites, with preliminary classification as H5-6 ordinary chondrites. Fe oxyhydroxides along metal-grain margins and within micrometer-scale secondary veins indicate moderate terrestrial weathering. Preliminary lipid analysis of the acidic fraction extracted from one meteorite and ten sediments reveals a larger diversity of carboxylic acids in the meteorite than in the sediments. For instance, n-alkanoic acid concentrations in sediments range from 0.25 to 13.54 µg/g dry weight (dw), with a mean of 3.53 ± 3.73 µg/g dw, whereas the meteorite sample contains 7.12 µg/g dw. Palmitic acid (n-C16) is the most abundant compound in both the meteorite and sediments, consistent with a biological source that may include microbial inputs [4]. Sediments from sedimentary traps and glacial valleys show higher n-alkanoic acid abundances than those from moraines and peripheral areas to the main mountain ranges. Although these Antarctic environments are characterized by extremely low biomass, the presence and distribution of lipid biomarkers in the meteorite suggest potential terrestrial contamination from local microorganisms. The 16S rRNA gene sequencing data are currently being processed and will be integrated with the lipid results to further assess potential biological inputs.

References: [1] Lee & Bland (2004) GCA, 68(4), 893-916. [2] Maeda et al. (2023) MAPS, 58(7), 1018-1038. [3] Sephton et al. (2004) MAPS, 39(5), 747-754. [4] Finkel et al. (2023) Astrobiology, 23(5), 563-604.