# ExoMars TGO detects hydrogen chloride over Alba Mons and fresh fissures, pointing to magma

- Published: 2026-11-14 03:14 UTC
- Section: Sky & Space › Astronomy
- Tags: Mars volcanism, hydrogen chloride on Mars, Alba Mons, ExoMars Trace Gas Orbiter, Atmospheric Chemistry Suite, CaSSIS, Martian fissures, magma chamber, Science Advances
- URL: https://realtech.media/news/rt-b564ea0ae3e4f3943fb25fa0_exomars_tgo_detects/

**Spectrometers on the ExoMars orbiter found isolated HCl peaks in the cold season; the authors link them to fissures and magma bodies at depth.**

![ExoMars TGO detects hydrogen chloride over Alba Mons and fresh fissures, pointing to magma](https://realtech.media/media/2026/11/aded5cc65c5195bc.jpg)
*pro-physik*

A team led by Alexander Trokhimovskiy reported in Science Advances (4 November 2026) detections of hydrogen chloride (HCl) in the Martian atmosphere that are isolated in the Alba Mons region and occur in the cold aphelion season. The data come from the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter (TGO) of ESA. The authors interpret the signal as a possible sign of ongoing igneous processes in the Martian interior [1].

Mars has the largest volcanoes in the Solar System, but how active they are is not known. Orbital images suggest that some volcanoes were active within the last few million years, and seismometers have recorded marsquakes. New lava flows or eruptions have never been observed, and sulfur dioxide, which could indicate eruptions, has not been detected so far [1].

## HCl signal at Alba Mons

Earlier ACS observations found HCl widely, at part-per-billion levels, in the warm perihelion period; this was attributed to aerosol-atmospheric sources [1]. TGO first detected the gas in 2021. HCl follows a seasonal cycle: it peaks in northern-hemisphere winter and largely disappears in summer, and most of this variation appears tied to the dust and water cycles.

The new detections are an exception to that pattern. They recur in the same place and the same season, in early summer over volcanic fissures on the flanks of Alba Mons. The HCl was strongly confined in space and appeared right after the winter frost sublimated.

## Fissures and magma interpretation

Images from the CaSSIS camera on TGO showed fresh, narrow fissures in the area, under 1 meter wide [1]. In some cases they are hundreds of meters long and accompanied by color changes of the surface. The authors interpret them as potential pathways for HCl rooted in magmatic bodies at depth [1].

According to the researchers, in winter, at temperatures down to -120 °C, ice seals the fissures. When the ice sublimates in early summer, the release of chloride would be channeled through them, similar to some fumaroles on Earth. The discoloration may come from deposits left by gases escaping from the interior. The team suspects a link to a dormant magma chamber, a volcanic plumbing system under the surface.

Co-author Daniel Mège of the Space Research Centre of the Polish Academy of Sciences said the results suggest Mars retained enough internal heat for volcanic activity until recently and possibly still does. Much of the work consisted of testing other chemical processes in the Martian atmosphere that could explain the HCl.

## Sources

1. [Science Advances](https://doi.org/10.1126/sciadv.aeb9422)
2. [pro-physik](https://pro-physik.de/nachrichten/mars-orbiter-findet-hinweise-auf-vulkanismus)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-b564ea0ae3e4f3943fb25fa0_exomars_tgo_detects/