Thermal reactivity of organic molecules in the presence of chloride salts: implications for the in situ gas chromatography–mass spectrometry analyses on mars
Abstract
The detection of chloride salts along Curiosity's traverse is of significant interest for astrobiology, as these salts may help protect organic molecules from radiation-induced degradation on the Martian surface. This suggests that chloride-rich environments could represent promising targets for future investigation. However, in situ analyses of Martian rocks and soils conducted by the Sample Analysis at Mars (SAM) instrument suite onboard the Curiosity rover, and likely by the GC-MS instruments onboard the Viking landers, have shown that chlorinebearing phases, such as perchlorates and chlorates, can react with organic molecules during thermal extraction from natural solid samples. The thermal decomposition of these oxidants can generate organochlorine compounds from indigenous Martian organic matter. Given the known reactivity of perchlorates and chlorates during pyrolysis-GC-MS, it is therefore important to assess whether chloride salts may also influence the detection of organic molecules. Here, we present a systematic laboratory study investigating the influence of three chloride salts likely present on Mars (MgCl₂, CaCl₂, and NaCl) on the detection of organic molecules by pyrolysis-GC-MS, as performed by the Viking and MSL missions, and planned for the upcoming ExoMars mission. Our results show that salt degradation, particularly through the release of hydrogen chloride, alters the nature, abundance, and distribution of pyrolysis products. Furthermore, we demonstrate that organic molecules and chlorides may act as precursors to the chlorohydrocarbons already detected on Mars. These findings indicate that chloride salts can significantly influence both the detectability and interpretation of organic compounds in Martian samples.
Related
- Evidence for phenylium reactivity under interstellar-relevant conditions
- Ion useful yields and relative sensitivity factors in Mn–Cr isotope measurements of carbonates by secondary ion mass spectrometry
- The existence of null points of flow and magnetic fields as prerequisites for the presence of astropauses and their co-location
- How Interstellar Gas and Ice Build Organic Molecules
- Axion Electrodynamics in Presence of a Stellar Non-homogeneous Background Magnetic Field
BibTeX
@article{mcintosh2026thermal,
title = {{Thermal reactivity of organic molecules in the presence of chloride salts: implications for the in situ gas chromatography–mass spectrometry analyses on mars}},
author = {Ophélie Mcintosh and Maeva Millan and A. Buch and Caroline Freissinet and J. Brucato and Cyril Szopa},
journal = {Icarus},
year = {2026},
month = oct,
doi = {10.1016/j.icarus.2026.117359},
url = {https://hal.science/hal-05839004v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Thermal reactivity of organic molecules in the presence of chloride salts: implications for the in situ gas chromatography–mass spectrometry analyses on mars
AU - Ophélie Mcintosh
AU - Maeva Millan
AU - A. Buch
AU - Caroline Freissinet
AU - J. Brucato
AU - Cyril Szopa
PY - 2026
DA - 2026/10/17
JO - Icarus
DO - 10.1016/j.icarus.2026.117359
UR - https://hal.science/hal-05839004v1
AB - The detection of chloride salts along Curiosity's traverse is of significant interest for astrobiology, as these salts may help protect organic molecules from radiation-induced degradation on the Martian surface. This suggests that chloride-rich environments could represent promising targets for future investigation. However, in situ analyses of Martian rocks and soils conducted by the Sample Analysis at Mars (SAM) instrument suite onboard the Curiosity rover, and likely by the GC-MS instruments onboard the Viking landers, have shown that chlorinebearing phases, such as perchlorates and chlorates, can react with organic molecules during thermal extraction from natural solid samples. The thermal decomposition of these oxidants can generate organochlorine compounds from indigenous Martian organic matter. Given the known reactivity of perchlorates and chlorates during pyrolysis-GC-MS, it is therefore important to assess whether chloride salts may also influence the detection of organic molecules. Here, we present a systematic laboratory study investigating the influence of three chloride salts likely present on Mars (MgCl₂, CaCl₂, and NaCl) on the detection of organic molecules by pyrolysis-GC-MS, as performed by the Viking and MSL missions, and planned for the upcoming ExoMars mission. Our results show that salt degradation, particularly through the release of hydrogen chloride, alters the nature, abundance, and distribution of pyrolysis products. Furthermore, we demonstrate that organic molecules and chlorides may act as precursors to the chlorohydrocarbons already detected on Mars. These findings indicate that chloride salts can significantly influence both the detectability and interpretation of organic compounds in Martian samples.
SN - 0019-1035
SN - 1090-2643
ER -