Hydrogen Chloride Traces Reveal Active Magma Beneath Alba Mons
Fresh fractures mapped across the flanks of Mars’ widest volcano suggest underground magma still releases volcanic gases.
Researchers detected hydrogen chloride lingering above Alba Mons during the northern Martian summer when the gas has vanished elsewhere on the planet.
An international team working with the European Space Agency’s ExoMars Trace Gas Orbiter published the findings in Science Advances on November 4, 2026. Alexander Trokhimovskiy of the Space Research Institute in Moscow led the study alongside Daniel Mège of the Space Research Centre at the Polish Academy of Sciences.
Detecting Gas Through Solar Occultation
The Trace Gas Orbiter uses the Atmospheric Chemistry Suite, a collection of infrared spectrometers operating via solar occultation. These instruments measure which wavelengths of sunlight are absorbed as the spacecraft watches the sun rise or set through the thin Martian atmosphere. Each gas leaves a distinct fingerprint, allowing scientists to detect chemical traces at parts-per-billion levels.
While hydrogen chloride typically appears during the warm, dusty season when Mars passes closest to the sun, observations from northern summer revealed anomalies. The orbiter detected the gas over Alba Mons when the entire atmosphere was cold and dry.
Mars may not be geologically dead after all. 🔴 Our ExoMars Trace Gas Orbiter has detected hydrogen chloride above volcanic fissures in the Alba Mons region, which scientists suggest could be linked to dormant volcanic activity beneath the surface. Read more:… pic.twitter.com/7D4B8MggQi
Mapping Fissures on Martian Ridges
Researchers examined the ground beneath the detection points using three different cameras: CaSSIS on the Trace Gas Orbiter, and HiRISE and CTX on NASA’s Mars Reconnaissance Orbiter. They identified linear swarms of fractures measuring tens of centimeters wide and hundreds of meters long. One of the CaSSIS images capturing these fissures was obtained on February 3, 2023, following earlier cold-season detections gathered between 2019 and 2021.
The cracks cut through the ice-rich cover of dust and frost across northern latitudes, indicating they are less than one million years old. Seasonal ice seals these fissures when temperatures drop to roughly minus 120 degrees Celsius. When that ice turns directly to vapor in the early summer, trapped gas escapes at an estimated rate of under three kilograms per second.
Evaluating Subsurface Life Potential
Alba Mons spans at least 1,350 kilometers from its summit, covering an area comparable to the United States while rising only about 6.8 kilometers high. Although no magma or active eruptions have ever been observed, subsurface warmth meeting ground ice could maintain pockets of liquid water. If hydrothermal systems are active, they could contain the ingredients and energy needed for microorganisms to evolve,” Daniel Mège said.
Colin Wilson, ESA project scientist for the orbiter, stated that the results “could turn out to be TGO’s biggest success to date.” The next early northern summer on Mars—when the seasonal model predicts the gas will return over Alba Mons—begins around April 2027.
Frequently Asked Questions
Are there active volcanoes on Mars?
No eruptions have ever been observed directly on Mars. However, hydrogen chloride detected over Alba Mons during the cold season suggests underground magma may still release gas, pointing to a dormant rather than extinct planet.
What makes Alba Mons unique compared to other Martian volcanoes?
Alba Mons is a shield volcano in the northern Tharsis region with lava flows extending at least 1,350 kilometers from its summit. Despite covering an area comparable to the United States, it reaches a height of only about 6.8 kilometers.
When is the next observation window for the Alba Mons gas?
The next early northern summer on Mars begins around April 2027. The Trace Gas Orbiter remains in position to check if the seasonal model successfully predicts the return of hydrogen chloride over the region.