^1,2Gustavo P. Maia, ²Laurent Remusat, ^2,3Kana Amano, ²Jean-Christophe Viennet, ^4,5,6Jason P. Dworkin, ^4,5,6Hannah L. McLain, ¹José A.L. da Silva
Earth and Planetary Science Letters, 692, 120237 Open Source Link to Article [DOI: 10.1016/j.epsl.2026.120237]
¹Centro de Química Estrutural, Institute of Molecular Sciences, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal
²Institut de Minéralogie, Physique des Matériaux et Cosmochimie, UMR CNRS 7590, Sorbonne Université, Muséum National d’Histoire Naturelle, Paris, France
³Institut d’Astrophysique Spatiale (IAS), Université Paris-Saclay, Orsay Cedex, 91405, France
⁴Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, USA
⁵Center for Space Science and Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA
⁶Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD, 20771, USA
Copyright Elsevier

Carbonaceous chondrites contain up to 4 wt% organic matter, likely inherited from precursors synthesised during preaccretion events. This organic inventory was later altered by hydrothermal and radiative processes, though the role of shock-induced impacts remains unclear. In this study, we examine the solid-state mechanochemical reactivity of hexamethylenetetramine (HMT) with sodium-rich montmorillonite (MMT) as an analogue to investigate the influence of shock- or impact-induced processes on organic matter evolution. HMT is reactive under mechanical stress, particularly when the clay mineral structure is disrupted, resulting in a wide range of molecules, including HMT-related compounds (as HMT-CH₃, HMT-OH, among others), pyrazine and triazinane/triazine derivatives. Notably, the incorporation of oxygen in N-rich species was also observed, despite the absence of liquid water. Conversely, when the clay mineral remains intact, mechanical input promotes the solid-state insertion of HMT-like molecules (as HMT, HMT-CH₃ and triazinane derivative) within its interlayer space, thereby protecting it from further reaction. The “cyclic mechanical input” delivered by laboratory milling (i.e., MM 200) and grinding (i.e., McCrone) is relevant to shock processes at an asteroid surface through repeated micrometeorite and IDPs impacts (i.e., space gardening). This work highlights shock/impact as a key factor driving both transformation and protection of extraterrestrial organics, offering new insights on how impact processes might have shaped extraterrestrial organic matter and consequent exogenous delivery of possibly prebiotic compounds to planetary surfaces.

¹E. Caminiti, ²P. Beck, ¹A. Wargnier, ²L. Bonal, ²B. Schmitt, ¹T. Usui
Icarus, (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117286]
¹Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara 252-5210, Kanagawa, Japan
²Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 414 rue de la piscine, 38400 Saint-Martin d’Hères, France
Copyright Elsevier

The spectroscopic properties of airless bodies are influenced by the space environment, including extreme temperatures. In this work, we study how low temperatures affect the spectral properties of meteorites in the visible to near-infrared wavelength range. We selected a Howardite-Eucrite-Diogenite meteorite, an ordinary chondrite, as well as seven carbonaceous chondrites of four different groups. Low-temperature reflectance spectroscopy measurements were acquired from 280 K down to 70 K over the 0.5–4 μm spectral range. We used spectral parameters to investigate changes during the cooling phase, including the position, depth, and full width at half maximum of the main absorption bands, as well as the position of interband peaks and spectral slope. We observed significant modifications in the position, amplitude, and width of absorption bands around 0.7, 1, 2, and 3 μm, as well as modifications of the position of interband peaks and average slope. The magnitude and trend of spectral modifications vary depending on the meteorite type. Spectral changes can influence the interpretation of the composition and the degree of hydration of meteorites and planetary objects. Moreover, even if CV and CO chondrites show comparable spectral properties, they exhibit different changes under temperature variations which may be used to distinguish their parent bodies. The effects of cryogenic temperatures on spectral properties must be considered when interpreting remote sensing data and comparing laboratory measurements with remote sensing observations. In the golden age of small body exploration, numerous space missions are affected, including but not limited to the Martian Moons eXploration (MMX, JAXA), Hera (ESA), Lucy (NASA), Tianwen-2 (CNSA), and Emirates Mission to the Asteroid Belt (EMA, UAE).