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Mars may not be as geologically quiet as scientists once believed. A remarkable discovery involving hydrogen chloride gas detected near the massive Alba Mons volcano is raising new questions about whether volcanic activity could still be occurring beneath the Red Planet’s surface.

An international team of researchers has identified unusual concentrations of hydrogen chloride (HCl) in the Martian atmosphere above a region containing volcanic fissures. The discovery, made using observations from the European Space Agency’s ExoMars Trace Gas Orbiter, suggests that gases may be escaping from underground magma systems.

The findings, published in the scientific journal Science Advances on November 4, 2026, provide intriguing evidence that Mars may still retain enough internal heat to support volcanic processes.

Although scientists have not observed an active eruption or flowing lava, the discovery could change how researchers understand the geological history of Mars. It may also have important implications for the search for life beyond Earth.

Hydrogen Chloride Gas Detected Near Alba Mons

The discovery centers on Alba Mons, one of the largest volcanoes on Mars and an enormous geological feature located in the planet’s Tharsis volcanic region.

Scientists analyzing atmospheric measurements from the ExoMars Trace Gas Orbiter noticed unusual concentrations of hydrogen chloride appearing above the northern flanks of Alba Mons.

Hydrogen chloride is a colorless gas that can be produced by volcanic activity. On Earth, it can escape from magma as molten rock rises toward the surface and releases dissolved gases.

The unusual Martian detections caught researchers’ attention because they appeared in a consistent geographic location and during a season when the gas was not expected to behave this way.

Rather than appearing randomly throughout the atmosphere, the hydrogen chloride signals were concentrated above volcanic fissures.

This raised the possibility that the gas was coming directly from beneath the Martian surface.

Researchers believe the observations could represent gas escaping from a dormant underground magma system.

What Is Alba Mons?

<bold>Alba Mons</bold> is a massive shield volcano located in the northern part of Mars’ Tharsis region.

Unlike steep-sided volcanoes commonly associated with explosive eruptions on Earth, shield volcanoes are generally broad structures formed by repeated flows of relatively fluid lava.

Alba Mons is particularly unusual because of its enormous size and relatively low profile.

Its volcanic structure covers an area comparable to the contiguous United States, making it the largest Martian volcano by surface area.

The volcano contains extensive lava deposits, fractures, and geological features that indicate a long history of volcanic activity.

Scientists have previously identified evidence suggesting that some Martian volcanic systems may have remained active much more recently than once believed.

The latest hydrogen chloride discovery adds another important piece of evidence to that growing scientific investigation.

How Scientists Detected the Mysterious Gas

The discovery was made possible by the European Space Agency’s ExoMars Trace Gas Orbiter, a spacecraft designed to investigate the chemical composition of the Martian atmosphere.

The spacecraft has been orbiting Mars since 2016 and began its primary science operations in 2018.

One of its key instruments, the Atmospheric Chemistry Suite, uses infrared spectroscopy to identify gases in the atmosphere by measuring how they absorb sunlight.

This technology allows scientists to detect extremely small concentrations of atmospheric chemicals that would otherwise be difficult to identify.

Researchers had previously reported hydrogen chloride in the Martian atmosphere in 2021. However, explaining its presence proved challenging because the gas can also be associated with atmospheric dust and water-ice processes.

The latest investigation uncovered unusual hydrogen chloride signals repeatedly appearing near Alba Mons.

Scientists then examined high-resolution images from another Trace Gas Orbiter instrument, the Colour and Stereo Surface Imaging System (CaSSIS).

These images revealed narrow fissures along the volcano’s flanks, some extending hundreds of meters across the Martian landscape.

Researchers noticed that the fissures were associated with changes in surface coloration, potentially indicating deposits left behind by escaping gases.

The combination of atmospheric measurements and geological observations strengthened the possibility that hydrogen chloride was originating from underground volcanic activity.

Could Magma Still Be Moving Beneath Mars?

One of the most exciting possibilities raised by the discovery is that magma may still exist beneath the Martian surface.

Mars has long been considered a planet whose major volcanic activity ended millions of years ago. Its enormous volcanoes are reminders of a much more active geological past.

However, the planet’s interior may not have completely cooled.

Scientists believe the hydrogen chloride could be released as underground magma rises and experiences decreasing pressure.

As the magma moves through fractures in the Martian crust, gases may escape and travel toward the surface.

Researchers suggest that an underground magma chamber could be responsible for the emissions observed near Alba Mons.

The process may resemble volcanic gas emissions found around dormant volcanic systems on Earth.

There is an additional explanation for why the gas appears at particular times.

During the Martian winter, extremely cold temperatures can cause ice to accumulate within surface fissures, potentially blocking the release of underground gases.

As temperatures rise during the northern hemisphere’s early summer, the ice sublimates directly into water vapor, allowing trapped gases to escape.

This seasonal process could explain why scientists repeatedly detected hydrogen chloride above the same volcanic region.

Importantly, the discovery does not prove that an eruption is imminent. Instead, it suggests that geological processes associated with magma may still be occurring beneath Mars.

Mars May Still Have Active Volcanic Systems

The discovery adds to a growing collection of evidence suggesting Mars may not be completely geologically dormant.

NASA’s InSight lander, which operated on Mars from 2018 through 2022, detected more than 1,300 seismic events, commonly called marsquakes.

These earthquakes demonstrated that Mars continues to experience geological activity beneath its surface.

Scientists have also identified relatively young volcanic formations and lava deposits that suggest some volcanic systems remained active within the planet’s more recent geological history.

The hydrogen chloride discovery provides another potential indication that Mars may still have underground volcanic activity.

However, researchers emphasize that there is currently no definitive confirmation of an active eruption, flowing lava, or a continuously operating magma chamber.

More observations will be necessary to determine exactly where the gas originates and whether molten rock is still moving beneath the surface.

Could Volcanic Activity on Mars Support Life?

Perhaps the most fascinating implication of this discovery involves the possibility of microbial life.

Scientists searching for extraterrestrial life have long considered Mars one of the most promising places to investigate.

Although the planet’s surface is extremely cold, dry, and exposed to radiation, conditions beneath the surface could be considerably different.

If magma is still present beneath Alba Mons, it could potentially heat underground water deposits.

The interaction between hot volcanic rock and water can create hydrothermal systems.

On Earth, hydrothermal environments support diverse microbial communities, even in locations where sunlight cannot reach.

These environments can provide microorganisms with:

• Heat from geological activity.
• Water necessary for biological processes.
• Chemical energy that microorganisms can use.
• Minerals and other potentially important nutrients.
• Protection from harmful surface radiation.

Researchers believe similar environments could potentially exist beneath the Martian surface.

If hydrothermal activity is occurring near Alba Mons, the surrounding fissures could become interesting targets for future Mars exploration missions.

Scientists would be particularly interested in determining whether underground water, heat, and suitable chemical ingredients coexist in the region.

It is important to understand that the discovery of hydrogen chloride is not evidence of life on Mars. However, it could help scientists identify locations where conditions might be suitable for microbial organisms.

Why This Discovery Matters for Future Mars Exploration

The hydrogen chloride discovery could influence how scientists prioritize future Mars exploration missions.

Until recently, researchers searching for evidence of life have focused heavily on ancient riverbeds, dried lake deposits, and locations where liquid water may have existed billions of years ago.

These locations remain important because they may preserve evidence of ancient microbial life.

However, the possibility of ongoing underground volcanic activity introduces another interesting target.

Instead of looking exclusively for signs of life that existed in Mars’ distant past, scientists may have additional reasons to investigate environments that could still contain heat and liquid water today.

Future robotic missions could potentially investigate the Alba Mons region using advanced imaging equipment, atmospheric sensors, and geological instruments.

A lander or rover equipped with appropriate scientific instruments could help determine whether the fissures are releasing volcanic gases and whether underground hydrothermal systems exist nearby.

Such discoveries could significantly expand our understanding of Mars and its potential to support life.

The ExoMars Trace Gas Orbiter Continues to Deliver Important Discoveries

The ExoMars Trace Gas Orbiter has become an important part of humanity’s effort to understand the Red Planet.

Developed through cooperation between the European Space Agency and Roscosmos, the spacecraft was designed to study trace gases in the Martian atmosphere and investigate potential biological and geological processes.

Its scientific instruments can detect extremely small quantities of atmospheric gases and help researchers understand how they are produced, transported, and removed.

The spacecraft has also returned detailed images of the Martian surface, allowing scientists to connect atmospheric observations with geological features.

The discovery near Alba Mons demonstrates the importance of combining different types of scientific measurements.

A small atmospheric signal might initially appear insignificant. However, when researchers compare that signal with surface geology and seasonal patterns, it can reveal something much more interesting about the planet.

Frequently Asked Questions About Hydrogen Chloride on Mars

1. What is hydrogen chloride gas?

Hydrogen chloride is a colorless chemical gas consisting of hydrogen and chlorine. It can be produced through volcanic processes and certain chemical reactions. When dissolved in water, it forms hydrochloric acid.

2. Where was hydrogen chloride detected on Mars?

Scientists detected unusual concentrations of hydrogen chloride above volcanic fissures along the northern flanks of Alba Mons in the Tharsis region of Mars.

3. Does hydrogen chloride prove that Mars has active volcanoes?

No. The discovery provides evidence consistent with possible underground volcanic activity, but scientists have not confirmed an active eruption or flowing magma.

4. What spacecraft discovered the hydrogen chloride?

The European Space Agency’s ExoMars Trace Gas Orbiter detected the gas using its Atmospheric Chemistry Suite instrument.

5. Could there be life beneath the surface of Mars?

It is possible that underground environments could provide heat, water, and chemical energy suitable for microbial life. However, scientists have not discovered confirmed evidence of living organisms on Mars.

6. Why is Alba Mons important?

Alba Mons is the largest Martian volcano by surface area. Its extensive volcanic features and newly investigated fissures make it an important location for studying the geological history and potential ongoing volcanic activity of Mars.

Final Thoughts: Mars May Not Be as Geologically Dead as We Thought

The discovery of hydrogen chloride gas near Alba Mons is another reminder that Mars continues to surprise scientists.

For decades, researchers have studied the planet’s enormous volcanoes, ancient lava flows, dried river valleys, and mysterious geological formations. Much of that evidence has pointed toward a world that was once far more active than it is today.

Now, atmospheric observations from the ExoMars Trace Gas Orbiter are raising the possibility that some of that volcanic activity may not have completely ended.

If the hydrogen chloride is indeed escaping from underground magma systems, Mars could still retain enough internal heat to support volcanic processes.

Even more exciting is the possibility that underground volcanic activity could create hydrothermal environments where microbial life might survive.

There is still much to learn, and scientists will need additional observations before drawing definitive conclusions.

But one thing is clear: Mars may be a much more geologically interesting world than previously believed.

The search for life on the Red Planet may ultimately lead scientists not just to ancient riverbeds and dried lake deposits, but also to the hidden volcanic systems beneath its surface.