Overview
- The ExoMars Trace Gas Orbiter team published their analysis on Wednesday, Nov. 4, 2026, reporting repeated, localized spikes of hydrogen chloride (HCl) in the atmosphere above the northern flanks of Alba Mons.
- TGO's Atmospheric Chemistry Suite measured the HCl and the CaSSIS camera then imaged fresh narrow fissures and nearby surface discoloration at the same sites, linking the gas to specific ground openings.
- Researchers propose a seasonal release mechanism in which ice seals fissure vents in winter and sublimation in early northern summer frees trapped magmatic gases, producing the recurring HCl spikes.
- The team interprets the HCl as a magmatic gas released from chlorine-bearing compounds in rising magma, which implies a dormant magma plumbing system and retained internal heat but does not prove active eruptions.
- If subsurface magma meets groundwater, the resulting hydrothermal environments would be prime targets for searches for microbial life and for future in‑situ measurements, thermal mapping, and seismic monitoring to confirm the hypothesis.