Abstract_EANA2025-31

Abstract EANA2025-31

Solid-state mechanochemistry of extraterrestrial organic molecules: new insights on the exogenous delivery of organic matter

Gustavo P. Maia (1,2), José A. L. da Silva (1), Kana Amano (2), Jean-Christophe Viennet (2), Jason P. Dworkin (3), Hannah L. McLain (3,4,5), and Laurent Remusat (2)

(1) Centro de Química Estrutural, Institute of Molecular Sciences, Instituto Superior Técnico, University of Lisbon, Portugal (2) Institut de Minéralogie, Physique des Matériaux et Cosmochimie, Muséum National d’Histoire Naturelle, France (3) Solar System Exploration Division, NASA Goddard Space Flight Center, USA (4) Department of Physics, The Catholic University of America, USA (5) Center for Research and Exploration in Space Science and Technology, NASA/GSFC, USA

Extraterrestrial delivery has been pointed out as one plausible source of relevant prebiotic organic molecules [1,2]. It is assumed that most of these molecules were delivered to the surface of the early Earth, which might have contributed to the emergence of life. We evaluate the hypothesis that some of the molecules found in extraterrestrial samples are the product of mechanochemical-induced reactions. They may occur during parent body disruptions, micrometeorite/interstellar dust particle collisions (i.e. space gardening), or atmospheric entry. This process remains poorly understood in cosmochemistry and could contribute to the wide range of extraterrestrial organic matter found on meteorite and asteroid samples.

In this work, the mechanochemical reaction applied to 5 wt% of hexamethylenetetramine (HMT, C6H12N4, Sigma-Aldrich, > 99%) in the presence of clay mineral Na-montmorillonite (MMT, SWy-2 Clay Minerals Society). The gridding experiments were performed on Retsch® Mixer Mill MM 200 (i.e. 25 Hz, 90 min), with a 10 mL tungsten carbide vessel with a 10 mm ball of the same material, and Retsch® XRD McCrone (i.e. 25 Hz, 90 min) using cylindrical grinding elements made of agate inserted into a 150 mL polypropylene (PP) vessel. The resultant powder was analyzed by Fourier Transform Infrared spectroscopy - Attenuated total reflection, FTIR-ATR, and powder X-Ray Diffraction, XRD. The soluble organic compounds were extracted with MiliQ H2O and a mixture of 1:1 Methanol/Dicloromethane (MeOH/DCM), on two separate aliquots, and analyzed by Proton Nuclear Magnetic Resonance, 1H NMR (i.e. 600 MHz) and Liquid chromatography–mass spectrometry (LC-MS).

FTIR and XRD of MM 200 sample revealed the destruction of the clay mineral, with the release of hydroxyl groups (i.e. bond to alumina) and interlayer H2O. HMT derivatives (e.g. HMT-CH3 and HMT-OH) together with a wide range of O-containing molecules were detected in the water extracts. Some of these compounds have been detected in meteorite samples (e.g. HMT-CH3 and HMT-OH).[3] Despite the lack of chemistry with McCrone gridding, preliminary vacuum powder XRD revealed the possibility of encapsulation of organics (i.e. HMT) into the Montmorillonite interlayer space. This data indicates that organics could be trapped within the clay interlayer space, by the action of mechanical energy (i.e. soft gridding). This may promote their preservation.

These experiments demonstrate that the evolution of extraterrestrial organic matter could be influenced by solid-state mechanochemistry (i.e. without liquid H2O). This study highlights the relevance of mechanical-induced reactions in extraterrestrial bodies. It then shed new light on the exogenous delivery of organic matter to the early Earth, and perhaps other terrestrial planets.

[1] Oba, Y. et al., Nat. Commun, 13, 2008 (2022). DOI: 10.1038/s41467-022-29612-x

[2] Furuwaka, Y. et al., Proc. Am. Acad. Arts Sci., 116, 24440-24445 (2019). DOI: 10.1073/pnas.1907169116

[3] Oba, Y., et al., Nat. Commun 11, 6243 (2020). DOI: 10.1038/s41467-020-20038-x