Mars may not be geologically dead after all. Hydrogen chloride gas detected in the planet’s thin atmosphere above cracks near the giant volcano Alba Mons points to magma still moving underground, according to a study published in Science Advances that links ESA’s Trace Gas Orbiter measurements to the planet’s deep interior.
Researchers analyzed readings from the Atmospheric Chemistry Suite aboard the European Space Agency’s ExoMars Trace Gas Orbiter and found anomalous concentrations of hydrogen chloride — HCl — on the order of a few parts per billion over the Alba Mons region, during the cold part of the Martian year when the planet sits near aphelion, its farthest point from the Sun. The highest concentrations lay above surface fractures identified only recently, which the team suggests could act as channels for emissions rising from below. The researchers write that low-altitude HCl detections, unexplained by the observed atmospheric conditions and models, together with the region’s geological context, point to a magmatic origin for the gas.
An off-season spike in the Martian air
The gas normally follows the seasons. Its concentration peaks during winter in the northern hemisphere and nearly vanishes in summer, a rhythm driven by the planet’s dust and water cycles. Yet the orbiter also recorded high HCl levels at the start of summer, directly above volcanic fissures on the slopes of Alba Mons, roughly two kilometres above the cracks. Atmospheric chemistry models could not account for the spike.
The Trace Gas Orbiter first detected gaseous hydrogen chloride in the Martian atmosphere in 2021, according to Mediafax.
Why chlorine hints at hidden magma
In the emissions of an active volcano, sulfur comes first, followed by hydrogen chloride in smaller amounts; during a volcano’s quiet periods, that ratio inverts. Martian meteorites that have fallen to Earth add another piece: Mars’s magma contains four times more chlorine than Earth’s magma. Read together, the researchers say, these clues amount to a signal of latent volcanism. ESA put it plainly: Mars is not geologically dead in its depths — it is simply asleep.
A volcano with a 1,600-kilometre crater
Alba Mons is a giant: its crater has a circumference of 1,600 kilometres, and the fissures around it date to about one million years ago — a blink on geological timescales. Mars hosts the largest volcanoes in the Solar System. Surface sensors have recorded marsquakes, but no eruption or fresh lava flow has ever been observed on the planet.
What the study does not show
The research does not directly demonstrate the existence of active magma, and it documents no eruption. The volcanic interpretation will have to be confirmed by further observations, the team cautions.
The life question beneath the crust
A magmatic system would also drive hydrothermal circulation — hot water and vapour rising through fissures toward the surface — creating temperatures and pressures that stay stable over time, independent of the atmosphere above, which is hostile to Earth life because of low temperatures and high radiation. Deși din punct de vedere geologic nu este moartă în cele mai profunde straturi, Marte se află pur și simplu într-o stare de repaus. Pe Pământ, viața a apărut în decurs de doar câteva milioane de ani; este foarte posibil ca un proces asemănător să fi avut loc și pe Marte.
