Hydrogen Chloride Hints at Volcanic Activity on Mars
Researchers detected the gas near Alba Volcano, the widest known volcano in the Solar System, suggesting possible hydrothermal activity beneath its surface.
Updated on Nov. 5, 2026 in Geology
An international team led by scientists affiliated with Russian and Polish academy-linked space research institutes detected hydrogen chloride gas on Mars, with findings published in the journal Science Advances. The gas was observed near Alba Volcano, which has a diameter of 600 kilometers.
Why it matters
The detection suggests volcanic or hydrothermal processes may still be active on Mars, which could inform where future exploration focuses. Researchers say the study is likely to provide an important basis for shaping Mars exploration plans.
Trace Gas Orbiter has detected hydrogen chloride across Mars since 2020, appearing in summer and disappearing in winter. The gas was detected near Alba Volcano during winter, despite average surface temperatures of minus 60 degrees Celsius, and whether a subsurface hydrothermal system is responsible remains unconfirmed.
The players
Trace Gas Orbiter
A spacecraft instrument mission that has monitored trace gases in the Martian atmosphere, enabling the long-term detection of hydrogen chloride across the planet.
The details
Compounds in Martian soil meet water vapor in the atmosphere, producing hydrogen chloride in summer. The gas leaks from thin fissures scattered across the surface of Alba Volcano, which the researchers link to a possible hydrothermal system.
Timeline
Since 2020: Trace Gas Orbiter begins detecting hydrogen chloride across Mars.
Winter: Hydrogen chloride is detected near Alba Volcano.
November 5, 2026: The team announces the detection findings.
Big Picture
This finding extends Trace Gas Orbiter's atmospheric record, which has tracked hydrogen chloride across Mars since 2020, by linking one of its seasonal gas signatures to a specific volcanic site. It adds evidence that Mars may retain geologic activity beyond what earlier surface studies had mapped.
The findings may shape where future Mars missions target their instruments, since a possible hydrothermal system could be a site of interest. Researchers suggest this work will guide exploration plans that are expected to take concrete form after a lunar base is constructed.
The takeaway
Hydrogen chloride appearing seasonally on Mars points to ongoing chemical activity beneath the surface. Tracking how such gases change over time could help scientists identify where geologic processes are still underway.
Further reading
For broader context on planetary surface processes, explore Geology.
