Scientists report evidence that hydrogen chloride gas is escaping from beneath Mars’ surface. Two outlets say the detection points to activity near surface fissures, with a specific focus on areas close to Alba Mons, where the gas is thought to be present in the atmosphere.
The findings come from observations described as using the ExoMars Trace Gas Orbiter, and they are published in *Science Advances* (dated November 4, 2026 in one report). The implications discussed across sources differ in emphasis: one frames the discovery as potentially indicating that volcanic activity could still be occurring deep underground, while another also links the same gas to broader questions about whether Mars is not fully volcanically dormant. It further raises the possibility that underground processes could create hydrothermal environments, which would be relevant to evaluating habitats for potential microbial life.
