Hydrogen chloride gas usually reaches its highest levels in Mars’s atmosphere during winter in the northern hemisphere, then mostly disappears in summer. Much of that seasonal pattern appears to follow the planet’s dust and water cycles. Above volcanic fissures on the flanks of Alba Mons, researchers found a recurring exception. Localized spikes of the gas appeared in the same place in early northern summer, raising the possibility of a source beneath the ground.
An international research team led by Alexander Trokhimovskiy suggests that the gas could be escaping from hot magma below the region. Its study, published November 4, 2026, in Science Advances, brings together atmospheric measurements and geological evidence to investigate a possible connection to dormant volcanism.
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