Active volcanoes on Mars? Noxious gas discovery says — maybe

The European Space Agency's Trace Gas Orbiter has detected hydrogen chloride, a noxious gas, coming from cracks in the surface of the Alba Mons volcano region on Mars. Hydrogen chloride is often produced by hot magma moving below the surface on Earth, suggesting Mars might still have active volcanic activity, according to scientists.

Mars' volcanoes, including Olympus Mons, the largest in the solar system, were once believed to be remnants of an active volcanic past. However, Mars has no tectonic plates to continuously reshape its surface, making it a largely dormant world for much of the space age. Recent findings, however, have challenged this notion.

NASA's InSight lander detected over 1,300 seismic events, revealing that Mars still experiences marsquakes, indicating potential volcanic activity. Additionally, evidence of relatively recent volcanic activity has been accumulating, leading to the discovery of hydrogen chloride in the Martian atmosphere.

The presence of hydrogen chloride at low altitudes, unexplained by observed atmospheric conditions and models, suggests an igneous origin, meaning it likely originated from volcanic activity. While other volcanic gases, such as sulfur dioxide, have been undetected, the seepage of halogen gases like hydrogen chloride could better identify active magma chambers.

The detection of hydrogen chloride above the Alba Mons region, during the cold season when it is typically difficult to observe, adds to the growing evidence of potential active volcanism on Mars today. The research, published in Science Advances on November 4, 2026, suggests that Mars may not be geologically dead, with magma possibly still flowing beneath its surface.