Hydrogen chloride measurements near Mars’s largest volcano by surface area, alongside newly identified cracks extending thousands of feet, add to the evidence that volcanic activity might continue there. Hot magma deep underground could be releasing the gas, researchers suggest. That interpretation rests on indirect evidence, and no eruption has been seen.
An international team studied Mars’s gradual release of hydrogen chloride through data gathered in 2021 by the European and Russian ExoMars Trace Gas Orbiter. In their paper in Science Advances, they describe unexpected rises in gas levels around the slopes of Alba Mons. The findings add another challenge to the view, long shared by many scientists, that the Martian interior is geologically dead.
Scientists already knew that hydrogen chloride emissions on Mars change with the seasons. The puzzle was why some increases happened in places and at times they hadn’t expected. Discovering fissures close to the Alba Mons readings drew researchers’ attention to the area, since the cracks could point to activity beneath the surface.
Discolored areas appeared along the fissures, whose lengths reach thousands of feet. The team suggests that gases seeping out could have deposited minerals, in a process resembling what happens at Earth’s volcanic gas vents. Together, these surface features and atmospheric readings point to recent or possibly ongoing geological activity. They don’t, however, establish that magma is active or that the detected gas came from those specific cracks.
“Our findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does,” said Polish Academy of Sciences professor Daniel Mège, a colead author of the study, in a statement about the research.
Mège described the orbiter’s detection in stronger terms: “The Trace Gas Orbiter was able to find the smoking gun,” he said. “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.”
The implications extend beyond the possibility of volcanism. Mars could have had abundant liquid water on its surface in the relatively recent past, the findings suggest, with a much thicker, warmer atmosphere than it has now. That possibility matters to research into ancient Martian life, but it isn’t evidence that life ever existed there.
The fissures themselves could give researchers a place to search for signs of past life. Mège’s reasoning depends on whether active hydrothermal systems exist beneath Alba Mons. If present, those systems could provide microorganisms with resources and protection from conditions at the surface.
“Looking for martian life in the seeping fissures of the Alba Mons region would make a lot of sense,” Mège argued. “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.”
