¹Ralph E. Milliken et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70179]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA
Published by arrangement with John Wiley & Sons

Near-Earth rubble-pile asteroids Bennu and Ryugu are part of the carbonaceous taxonomic complex (C-complex), and samples returned from both bodies resemble the most aqueously altered carbonaceous chondrites. However, telescopic and spacecraft visible–near infrared (VIS–NIR) reflectance spectra of Ryugu exhibit a red (positive) spectral slope, whereas Bennu has a blue (negative) spectral slope characteristic of the rare B-type subclass of asteroids. The asteroid spectra also suggest different levels of hydration, with Ryugu dominated by OH and Bennu containing spectral evidence of more H2O. To understand what causes these differences, we acquired VIS–NIR reflectance data (~0.3–5 μm) from a variety of Bennu samples over spatial scales of 100 μm to several millimeters. No single sample reproduces the average spectral properties of Bennu, but by evaluating samples of different petrology and physical states—groups of particles, isolated particles, and larger stones—we demonstrate that primary composition, and highly hydrated Mg-rich phosphate in particular, plays a strong role in controlling the spectral slope and average hydration absorption strength of Bennu materials. Bennu and Ryugu may be dominated by different lithologies originating from different regions of a common planetesimal, thus explaining their different spectral evolution. The spectral characteristics of B-type asteroids, particularly those with blue slopes at near-infrared wavelengths and broad hydration features at ~3 μm, may indicate the presence of Mg phosphate and thus a history of complex fluid–rock interactions relevant to prebiotic chemistry.

^1,2,3Rachael Lappan,^3,4Rachel S. Kirby,⁴Andrew G. Tomkins
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70178]
¹Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
²Securing Antarctica’s Environmental Future, Monash University, Melbourne, Victoria, Australia
³School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
⁴Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth, Western Australia,Australia
Published by arrangement with John Wiley & Sons

Since the discovery of nine meteorites near the Yamato mountains in 1969, Antarctica has been recognized as a superb location for meteorite recovery. While Antarctic recovery expeditions prioritize meteorite preservation for mineralogical and planetary studies, meteorites are not typically collected for biological applications. The LifeMet expedition was the first Australian Antarctic meteorite recovery expedition, conducted in the 2024–2025 austral summer in the Wohlthat and Orvin Mountains in Dronning Maud Land, Antarctica. The expedition had two primary objectives: (1) to examine whether Antarctic microorganisms colonize and consume nutrients from meteorites, providing insights into microbial ecosystem formation, interactions with uncommon minerals and extremophile survival strategies in Antarctica; and (2) to evaluate the practical and logistical factors influencing meteorite recovery in these regions, and the suitability of recovery approaches for biological sampling. A total of 13 stones, including one confirmed meteorite, were recovered. Adjacent environments (air, sediment, snow, ice, and terrestrial rocks) were sampled to characterize microbial sources. We found that low-altitude blue ice zones were poorly suited to meteorite recovery; however, microbe–meteorite interactions may be enhanced in these areas due to warmer temperatures and periodic ice melting. Our observations suggest that the low albedo of meteorites may promote the formation of periodically water-filled potholes and cryoconite, which may support microbial proliferation. In contrast, meteorites stranded on nunataks are minimally oxidized. Based on our observations at ~71°S, blue ice fields at altitudes above ~2000 m are better suited to meteorite recovery at current climatic conditions.