Mars Is Not Dead Yet

A European spacecraft circling Mars has detected a corrosive gas rising over narrow cracks on the flank of the volcano Alba Mons, and the team behind the finding says the likeliest source is a subsurface igneous system, a sign the planet may still hold internal heat ^[1][2].

The study, led by Alexander Trokhimovskiy, appeared in Science Advances on November 4, 2026, under the title "Enigmatic HCl detections as a potential signature of igneous activity on Mars" ^[1][2]. It is the strongest hint in years that Mars is not geologically finished. It is a hint, not a discovery of an eruption.

No new lava flows or eruptions have been observed ^[2][4]. What exists is an orbital measurement and a geological interpretation of it.

What the orbiter saw

The work combines two instruments on the ExoMars Trace Gas Orbiter, a joint European-Russian mission run by the European Space Agency. Its Atmospheric Chemistry Suite is a set of infrared spectrometers that identify gases by the way they absorb sunlight. Its CaSSIS camera photographs the ground ^[1][2][5].

The spectrometers found hydrogen chloride, a gas made of one hydrogen and one chlorine atom, in localized patches above fissures on Alba Mons's northern flank. It appeared in early northern summer, just after winter frost sublimates, which means turning straight from ice to vapor ^[2][3][4]. The concentration is on the order of two parts per billion by volume, according to co-author Daniel Mège. That is about two molecules of the gas in every billion of the surrounding air ^[3].

The camera shows narrow fissures, some hundreds of metres long, with changes in surface color around them. ESA's account features an image taken on February 3, 2023, at about 64.6 degrees north, 274.4 degrees east ^[1][2].

Why it was a surprise

Hydrogen chloride was a new find on Mars only recently. The orbiter first picked it up in observations from 2018, reported in 2021 ^[5][6]. Those detections were scattered across both hemispheres during a global dust storm, and researchers proposed an ordinary explanation: salty dust and atmospheric water reacting to make the gas ^[5][6].

That is why the gas is usually tied to seasonal weather on Mars, to its dust and water cycles ^[1][2][4][5]. A pulse of it in one northern place, in the same season, over visible cracks was the exception that sent the team looking for something else ^[4][5].

The proposed mechanism

The researchers suggest that winter ice acts as a lid over the fissures and blocks gas from escaping. When that ice sublimates in early summer, the lid lifts and hydrogen chloride seeps out ^[1][2][3]. They also suggest the discoloration could be material left behind by the escaping gas ^[1][2][3].

Both ideas are interpretation, not something anyone has watched happen ^[2][3]. The team describes a dormant magma chamber beneath the surface as one possible source, but the study reports no direct measurement of a chamber and does not confirm that one is active ^[1][2][4].

A planetary volcanologist who was not part of the study told National Geographic the source could be underground gas pockets or active magma, and noted that hydrogen chloride can also arise through chemical reactions ^[4]. Those are three different answers with very different meanings for Mars. Pockets of old gas would mean a leaky crust, while magma would mean a living interior.

Why a leaky volcano matters

Mars cooled as it lost heat, and for decades the working picture has been of a planet whose volcanoes went quiet long ago. Its volcanoes and its marsquakes have given reasons to wonder whether that is entirely true, but neither proves current volcanism at Alba Mons ^[2][4].

The new result adds something the others lack. It points to a specific place, on a specific season, with a specific gas and visible marks on the ground.

It also changes where scientists might look for life. If magma and groundwater meet beneath the fissures, hot water could circulate through the rock. Mège said active hydrothermal systems near the fissures could offer energy and protection that might make them useful places to search ^[2][3].

He was careful about the limit. Such systems need not contain living organisms, and hydrogen chloride is not a life-supporting gas ^[2][3]. The fissures are a reason to investigate, and nothing in the study says life is there.

What would settle it

The open questions are plain. Does the gas return over the same fissures in the same seasonal window? Can the team show it emerges from the mapped cracks rather than merely above the same region? Are the color changes deposits from the gas, and can their composition be identified? Does the hydrogen chloride come from magma, stored gas, or reactions between hot water and Martian minerals?

Nobody yet knows.

The researchers say continued observations by the orbiter, including searches for localized emissions elsewhere, could test the interpretation ^[2][3]. Other volcanic regions, such as Tharsis and Cerberus, are obvious places to check for a similar signal. If the gas turns up only at Alba Mons, the finding stays an oddity. If it turns up over other volcanic ground, a planet long written off as dead will need a new description.