Gas rising through Alba Mons fissures may be venting from hot magma

Gas rising through narrow fissures on the flanks of the Alba Mons volcano may be venting from hot magma below the Martian surface. The team's paper, published in Science Advances in 2026, reads the gas as a sign of dormant volcanism. Phys.org.

The mechanism starts with hydrogen chloride. The ExoMars Trace Gas Orbiter first reported the gas in the Martian atmosphere in 2021. On Earth it commonly escapes from magmatic vents, which led researchers to ask whether the same process was at work on Mars. Hydrogen chloride on Mars follows a seasonal pattern. It peaks in northern hemisphere winter and mostly disappears in summer, and most of that variability appears to be linked to the planet's dust and water cycles.

One exception stood out. The team noticed spikes in early summer in the northern hemisphere, always in the same season and at the same place, above volcanic fissures on the flanks of Alba Mons. The orbiter's Atmospheric Chemistry Suite, a set of infrared spectrometers, detected the gas strongly localized in space and at a time just after the winter frosts sublimate.

The geological half of the design came from the orbiter's CaSSIS camera. Images of the Alba Mons region showed fresh, narrow fissures, in some cases hundreds of meters long, associated with color changes on the surface. The discoloration could be deposits left by escaping gases, as around fumaroles, the volcanic gas vents found on Earth.

The proposed picture combines the two observations. Winter temperatures, down to -120°C (-184 degrees Fahrenheit), would leave the fissures blocked by ice. As the ice sublimates in early summer, the fissures would channel the release of chloride. The team suggests the seepage is connected to a dormant magma chamber, a sort of volcanic plumbing system under the surface.

Daniel Mège, a professor at the Space Research Center of the Polish Academy of Sciences and co-lead author of the paper, said the findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does. He said the spatial distribution of the seeping made it instantly obvious to him that something volcanic lay behind it, but that it had to be demonstrated. He added that a large part of the work was examining every possible chemical process in the Martian atmosphere to explain the hydrogen chloride. Mège also described the detection as finding a needle in a haystack, since the orbiter spotted a handful of molecules from a perhaps intermittent source while moving along its orbit.

The study fits earlier hints about Martian volcanism. Mars has the largest volcanoes in the solar system, but it is not known how active they are. Orbital imagery shows that some volcanoes appear to have been active within the last few million years, and seismometers have detected marsquakes. However, no new lava flows or eruptions have ever been observed.

Mège also said that looking for Martian life in the seeping fissures would make a lot of sense, since active hydrothermal systems could contain the ingredients and energy microorganisms need. Colin Wilson, ESA's project scientist for the orbiter, said the findings may prove to be the Trace Gas Orbiter's greatest success yet.

The link between the gas and a dormant magma chamber is a suggestion from the research team, and the European Space Agency reports that no new lava flows or eruptions have been observed.