Abstract EANA2025-180

Since the Viking mission (1975), pyrolysis coupled with gas chromatography and mass spectrometry (Pyr-GC-MS) has become a commonly used technique in space exploration missions [1], [2]. In this context, the analysis of organic residues from interstellar and cometary ice analogues by high-resolution pyrolysis-GC-MS (Orbitrap) follows the analytical protocols developed in astrochemistry. Previous studies on refractory organic residues derived from such ices have revealed a high molecular diversity, notably including hexamethylenetetramine (HMT, C₆H₁₂N₄) [3], [4]. This stable polyheterocyclic molecule is of particular interest for understanding abiotic formation pathways of prebiotic organic compounds [5].

We explored various pyrolysis techniques, either coupled or not with gas chromatography, and all coupled to high-resolution mass spectrometry (Orbitrap), including evolved gas analysis (EGA-MS) and thermal desorption (TD-GC-MS). In this study, a pre-cometary organic analogue was analyzed using a Pyrolyzer-GC-FT-Orbitrap-MS configuration. EGA-MS analysis revealed two major desorption profiles. The high mass resolution of the Orbitrap enabled the identification of hexamethylenetetramine (HMT) during the first thermal event, with a mass error of less than 2 ppm, as well as the detection of an HCN-type polymer in the second desorption profile [3]. This method provides a first insight into the molecular composition and the desorption temperatures of these compounds. The TD-GC-MS analysis further confirmed the presence of HMT and identified several of its derivatives, in agreement with previous literature [6], [7].

This methodology was then applied to several carbonaceous chondrites (e.g., Paris, Murchison, Aguas Zarcas, Tarda, NWA), analyzed directly without any prior sample preparation, with the aim of evaluating the relevance of high-resolution pyrolyzer–GC–MS coupling for the analysis of complex extraterrestrial organic matter. Data were successfully acquired, but are still being processed due to the density and complexity of the information obtained. The presentation will focus on the results from the ice analogues, particularly the detection of HMT and its derivatives, as well as the application of the methodology to meteorites and the current challenges encountered, thereby paving the way for optimized data processing strategies in an astrochemical context.

1.          Anderson, D. M. et al. Mass spectrometric analysis of organic compounds, water and volatile constituents in the atmosphere and surface of Mars: The Viking Mars Lander. Icarus 16, 111–138 (1972).

2.          Goesmann, F. et al. Cosac, The Cometary Sampling and Composition Experiment on Philae. Space Sci Rev 128, 257–280 (2007).

3.          Vinogradoff, V. et al. The mechanism of hexamethylenetetramine (HMT) formation in the solid state at low temperature. Physical Chemistry Chemical Physics 14, 12309 (2012).

4.          Vinogradoff, V., Duvernay, F., Danger, G., Theulé, P. & Chiavassa, T. New insight into the formation of hexamethylenetetramine (HMT) in interstellar and cometary ice analogs. Astron Astrophys 530, A128 (2011).

5.          Oba, Y. et al. Extraterrestrial hexamethylenetetramine in meteorites—a precursor of prebiotic chemistry in the inner solar system. Nat Commun 11, 6243 (2020).

6.          Muñoz Caro, G. M. & Schutte, W. A. UV-photoprocessing of interstellar ice analogs: New infrared spectroscopic results. Astron Astrophys 412, 121–132 (2003).

7.          del Burgo Olivares, C. et al. Synthesis of new hexamethylenetetramine-based products (HMT-R) in UV-irradiated pre-cometary ice analogues. Astron Astrophys 698, A285 (2025).