Abstract EANA2025-35

Introduction: The presence of secondary alteration minerals including phyllosilicates, magnetite, and carbonates in CI chondrites have been inferred to indicate that their parent body asteroids have been aqueously altered (1). Many organic synthesis processes have been identified as simultaneously occurring within these parent bodies (2). Analysing the soluble organic matter (SOM) produced under analogous hydrothermal conditions can elucidate the chemical pathways involved in this alteration within CI chondrite precursor asteroids (3), and even asteroids Ryugu and Bennu (4,5.)

Various asteroidal analogue experiments have previously been performed, but these have been non-specific in terms of conditions and minerals utilised (3,6.) The influence of carbonate and saponite on SOM produced from parent body alteration processes remains to be investigated. This project will therefore examine the effects of carbonate and saponite on organic synthesis in an analogue system for hydrothermal alteration in a CI chondrite parent body.

Samples and methods: Hexamethylenetetramine (HMT) solutions, as well as combinations of water, HMT, saponite and carbonate, were heated at 150ᵒC and pH 10 for either 7, 30 or 60 days. Inductively coupled plasma optical emission spectroscopy (ICP-OES) and Fourier-transform infrared (FTIR) spectroscopy were used to investigate the solutions’ salt abundances. Gas chromatography-mass spectrometry (GC-MS) was also utilised for detailed identification of the amino acids synthesised.

Results: Comparison of the concentrations of Al, Ca, Fe, Mg and Na cations across different samples shows that samples containing greater proportions of carbonate have higher concentrations of Ca and Fe. Concentrations of all cations decrease from 7 to 60 days, but Mg shows an increase at 30 days while the other species only decrease. Principal Components Analysis (PCA) of the elemental composition of this data shows Ca clustering with Fe, while Al and Mg cluster separately.

Preliminary FTIR results suggest the presence of a wide range of organics across the samples, including acetate and formate groups. Various amino acids are being identified in the aqueous fraction such as glycine, β-alanine and alanine – including an apparent enrichment in D- versus L-Alanine.

Discussion: The elevated cation concentrations in these samples suggests that multiple types of salt have been generated - potentially organic salts such as magnesium formate and iron acetate, which seem to be supported by preliminary FTIR data. The surface of saponite, for instance, could have enhanced complex formation, resulting in these organic salts (6.) Distinct kinetic pathways controlling calcite and possible brucite formation likely occurred, but the kinetics of similar chemical systems is poorly understood, and more mechanistic studies are needed concerning the formation of these salts. Incoming FTIR data is planned to further elucidate the composition of the liquid fraction, and therefore which reactions formed the species observed.

The analysis of amino acid composition data from these liquid samples should bring further insight into the kinds of chemical pathways that acted under hydrothermal conditions, since such investigation has been successfully applied to carbonaceous chondrites in the past, allowing for the inference of certain reactions like Strecker synthesis happening in their parent bodies (7.)

References:

[1] Brearley A. J. (2006) Meteorites and the early solar system II, 943, 587-624.

[2] Kebukawa Y. et al. (2017) Science advances, 3(3).

[3] Vinogradoff V. et al. (2017) Icarus, 305, 358-370.

[4] Chan Q. et al. (2023) In Hayabusa2 International Symposium.

[5] Zega T. J. et al. (2024) LPI Contributions, 3036, 6450.

[6] Serra C. et al. (2024) Icarus, 423, 116-273.

[7] Botta O. et al. (2002) Origins of Life and Evolution of the Biosphere, 32, 143-163.