Mars may not be volcanically dormant after all: Hydrogen chloride discovery raises questions about underground magma and possible life
Scientists detect volcanic gas above fissures near Alba Mons, offering fresh evidence that Mars may still retain geological activity beneath its surfaceFor decades, Mars has been regarded as a planet whose volcanic activity largely belongs to its distant past. However, a new discovery by an international team of researchers has brought fresh attention to the possibility that the Red Planet may still have a geologically active interior.Scientists have detected hydrogen chloride (HCl) in the Martian atmosphere above narrow fissures on the northern flanks of Alba Mons, one of the largest volcanoes in the Solar System by surface area. The findings, published in Science Advances on November 4, 2026, are based on observations from the European-Russian ExoMars Trace Gas Orbiter.
Why did scientists believe Mars was volcanically dormant?
Mars is home to enormous volcanic formations, including Olympus Mons and Alba Mons. However, unlike Earth, the planet has not displayed clearly observed modern volcanic eruptions or fresh lava flows.Scientists have long considered Mars relatively inactive because its geological activity has declined considerably from its early history. Its smaller size compared with Earth meant that it lost internal heat more rapidly. The absence of Earth-like active plate tectonics also means that Mars does not experience the same continuous geological recycling.Although orbital images have indicated volcanic activity within the past few million years, direct evidence of present-day magmatic activity has remained elusive.
Sulfur fumarole next to a crater in Hawaii. Credits: US Geological Survey
How can atmospheric gases reveal activity beneath the surface?
The detection of hydrogen chloride has offered researchers a possible way to investigate what is happening underground.On Earth, hydrogen chloride is commonly associated with volcanic gas emissions. It can escape when magma rises and pressure decreases, releasing gases from compounds dissolved within molten rock.The ExoMars Trace Gas Orbiter uses infrared spectrometers to identify gases through their characteristic absorption signatures in the atmosphere. Researchers identified unusual concentrations of hydrogen chloride above the Alba Mons region.Further observations using the spacecraft’s CaSSIS camera revealed narrow surface fissures, some extending hundreds of metres, along with changes in the surrounding surface colour.Scientists suggest that these fractures could provide pathways for gases escaping from an underground magmatic system. Seasonal changes may also play a role, as winter ice can block the openings before melting or sublimating in early summer.The findings do not confirm an ongoing eruption, but they offer evidence consistent with volcanic processes beneath the Martian surface.
Could underground volcanic heat support microbial life?
The discovery has also attracted interest because of its implications for the search for life beyond Earth.If underground magma comes into contact with subsurface water, it could generate hydrothermal environments. Such systems can provide heat, chemical energy and minerals that microorganisms may use to survive.On Earth, hydrothermal environments support microbial communities even in places without sunlight. Similar conditions beneath Mars could potentially offer protection from the planet’s harsh surface environment and radiation.Researchers believe the fissures around Alba Mons could therefore be important locations for future investigations into possible subsurface habitats.However, the presence of hydrogen chloride does not establish that liquid water or microbial life exists there. Further observations will be needed to determine the source of the gas and whether suitable underground conditions are present.
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