# ExoMars TGO detected localized HCl over Mars volcano Alba Mons in northern summer - Published: 2026-11-05 05:41 UTC - Section: Sky & Space › Space - Tags: Mars volcanic activity, Alba Mons, hydrogen chloride on Mars, ExoMars Trace Gas Orbiter, Atmospheric Chemistry Suite, CaSSIS camera, Martian fissures, Daniel Mège, Alexander Trokhimovskiy, Mars magma chamber - URL: https://realtech.media/news/rt-b2319b3a4068f7ab578b4e35_exomars_tgo_detected/ **The orbiter's spectrometers recorded hydrogen chloride in a season when it is normally absent; the team links it to fissures, but active volcanism is not proven.** ![ExoMars TGO detected localized HCl over Mars volcano Alba Mons in northern summer](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/f9609696c18e164f.webp) *scinexx* A research team led by Alexander Trokhimovskiy and Daniel Mège combined observations from the European ExoMars Trace Gas Orbiter (TGO) with geological images of the Alba Mons region on Mars. According to scinexx, the infrared spectrometers of the Atmospheric Chemistry Suite (ACS) recorded localized hydrogen chloride (HCl) signals there in early northern summer. [1] Mège works at the Space Research Centre of the Polish Academy of Sciences in Warsaw. ## Gas signal in the wrong season No fresh eruptions or new lava flows have been observed directly on Mars. Some geologically young surface forms and recorded marsquakes suggest, however, that the planet's interior has not fully solidified. [1] On Earth, HCl can escape from volcanic vents. On Mars it also forms through processes linked to raised dust, water vapor and seasonal climate changes, so its detection alone does not prove volcanic activity. Normally the gas reaches its highest concentrations in other seasons and largely disappears during northern summer. [1] HCl was first reported in the Martian atmosphere in 2021. Those signals were widespread and fitted reactions between dust, water vapor and the atmosphere better than a volcanic source. The repeated, spatially confined observations near Alba Mons stand out against that background. A conference abstract published in 2025 already describes such exceptions to the usual seasonal pattern. [1] ## Fissures as a possible gas pathway The team examined the terrain around the measurement sites with the orbiter's CaSSIS color camera and other high-resolution images. The area contains narrow fissures, in places several hundred meters long. Some are surrounded by light or dark discoloration that could be consistent with deposits from escaping gases. [1] The proposed explanation is that gases from a deep, still-warm magma chamber rise along such cracks. In the extremely cold winter, ice would temporarily seal the fissures. When the frost sublimates in northern summer, trapped substances could escape and produce locally elevated HCl. [1] “Our results suggest that Mars has retained enough internal heat to allow volcanic activity into the recent past, possibly even to the present day,” said Mège. [1] The proximity of gas signals and fissures supports this idea but does not settle the cause. It remains to be checked whether the discolorations come from subsurface gases and whether the fissures are still permeable. Chemical processes without magma also have to be considered as the source of the HCl. [1] Mège also noted that hydrothermal systems, if active, could supply water, heat and chemical energy. This is a possibility, not evidence of liquid water or life at the fissures. The paper, announced for 4 November 2026 in Science Advances (doi: 10.1126/sciadv.aeb9422), is to substantiate the link between the atmospheric signals and the terrain. Its full text could not be independently verified when this report was prepared. [1] ## Sources 1. [scinexx](https://www.scinexx.de/news/kosmos/marsorbiter-hat-hinweise-auf-vulkanische-aktivitaet-des-roten-planeten-entdeckt) --- Source: RealTech, realtech.media — https://realtech.media/news/rt-b2319b3a4068f7ab578b4e35_exomars_tgo_detected/