Scientists have found hydrogen chloride near Mars’s Alba Mons volcano, strengthening the case for possible underground volcanic activity. The study, published online on November 4 in Science Advances, combines atmospheric measurements with images of surface fractures. The international team interprets the gas as a potential sign of buried magma, rather than evidence of an observed eruption.
According to the European Space Agency, the ExoMars Trace Gas Orbiter first reported this gas in 2021. Most seasonal variations appear linked to dust and water cycles: concentrations rise in northern winter and largely vanish in summer. Near Alba Mons, however, researchers found an unusual early-summer signal. The broad volcano lies in the northern hemisphere and is Mars’s largest by surface area, Reuters reported.
The orbiter’s Atmospheric Chemistry Suite detected the localized gas, while its CaSSIS camera revealed fresh, narrow fissures and changes in surface colour. Daniel Mège of the Polish Academy of Sciences told ESA that measured concentrations were around two molecules of hydrogen chloride per billion air molecules. Researchers propose that winter ice blocks pathways and that its disappearance allows trapped gas to escape.
The team assessed alternative atmospheric chemical explanations before favouring seepage from a magmatic source, Mège said. The observations do not directly show molten rock or establish that particular cracks are the source. National Geographic reported that the gas could also arise through chemical reactions involving hot water and chlorides. No new lava flow or eruption has been observed, ESA stressed.
If magma remains beneath the region, its heat could help create protected environments where groundwater and rock interact. Such hydrothermal settings are relevant to the search for microbial life, but the study has not detected organisms. Mège cautioned that even a hydrothermal system need not contain life. Further investigation must determine the gas’s origin and whether potentially habitable conditions actually exist.
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