New observations from the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) have revealed evidence that volcanic activity may still be occurring beneath the Martian surface. Researchers detected unusual concentrations of hydrogen chloride gas above volcanic fissures near Alba Mons, suggesting that gases from underground magma could be escaping into the atmosphere.
The findings, led by an international research team under Alexander Trokhimovskiy, indicate that Mars may retain enough internal heat to support dormant or intermittent volcanic processes. The study, published in Science Advances, offers new insights into the planet’s geological activity and the possibility of habitable environments beneath its surface.
Hydrogen Chloride Spikes Point to Possible Volcanic Activity
The ExoMars Trace Gas Orbiter first detected hydrogen chloride in the Martian atmosphere in 2021. On Earth, this gas is commonly released through magmatic vents, prompting scientists to investigate whether a similar process could be taking place on Mars.
Hydrogen chloride concentrations on Mars typically follow seasonal patterns. Levels generally peak during the northern hemisphere’s winter and decline during summer, with much of this variation associated with dust and water cycles.
However, researchers identified an unusual exception. During early summer, hydrogen chloride concentrations increased above volcanic fissures on the flanks of Alba Mons. The gas appeared repeatedly in the same location and season, suggesting a possible connection to geological activity beneath the surface.
“Our findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does,” says Daniel Mège, Professor at the Space Research Centre of the Polish Academy of Sciences and co-lead author of the study.
Fresh Fissures Reveal Possible Routes for Underground Gases
Researchers combined atmospheric observations with geological analysis to investigate the source of the hydrogen chloride. Infrared spectrometers aboard TGO’s Atmospheric Chemistry Suite detected the gas, while the spacecraft’s CaSSIS camera captured images of the Alba Mons region.
The images revealed narrow, apparently fresh fissures, some extending hundreds of metres, accompanied by changes in surface colour. Scientists believe these openings could provide pathways for magmatic gases to reach the Martian atmosphere.
“The Trace Gas Orbiter was able to find the smoking gun. It was like looking for a needle in a haystack. It’s truly amazing that it spotted a handful of molecules from a perhaps intermittent source, whilst moving continuously along its orbit to monitor the whole martian atmosphere,” explains Daniel.
The research team proposes that the fissures remain blocked by ice during the Martian winter, when temperatures can fall to -120°C. As temperatures rise in early summer and the ice sublimates, hydrogen chloride and other gases may escape through the openings.
The discolouration surrounding the fissures could also result from deposits left behind by escaping gases, similar to formations found around fumaroles, or volcanic gas vents, on Earth.
“Looking at the spatial distribution of the seeping, it became instantly obvious to me that there was something volcanic behind it, but it had to be demonstrated” concedes Daniel.
Scientists also examined alternative chemical processes that could explain the presence of hydrogen chloride before linking the observations to possible volcanic activity.
“A huge part of the work consisted of examining all the possible chemical processes going on in the martian atmosphere. We needed to be rigorous, critical and creative to explain the presence of hydrogen chloride. The data were complex, but also excellent brain food,” adds Daniel.
The researchers suggest that the gas release may be connected to a dormant magma chamber beneath Alba Mons, indicating that Mars could still have an active geological system deep underground.
Could Volcanic Activity Create Habitable Environments on Mars?
The findings also raise questions about the possibility of microbial life beneath the Martian surface. Magmatic gases may have been more abundant in the planet’s past, potentially contributing to a thicker atmosphere, warmer temperatures and conditions that allowed liquid water to exist across large areas.
Researchers suggest that interactions between rising magma and underground water could create warm environments suitable for microbial activity. Such hydrothermal systems could provide microorganisms with essential chemical ingredients and energy while offering protection from the harsh conditions on the surface.
“Looking for martian life in the seeping fissures of the Alba Mons region would make a lot of sense. If hydrothermal systems are active, they could contain the ingredients and energy needed for microorganisms to develop, and shield microorganisms from the hostile and changing environment above the surface,” ponders Daniel.
Although scientists have not observed any new lava flows or volcanic eruptions on Mars, evidence from orbital imagery and marsquake detections has already raised the possibility of recent or ongoing geological activity.
“These findings may prove to be TGO’s greatest success yet,” highlights Colin Wilson, ESA’s project scientist for the ExoMars Trace Gas Orbiter.
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