A spacecraft from the European Space Agency has found hydrogen chloride gas above cracks near Alba Mons, one of Mars’s biggest volcanoes. This discovery was made by the ExoMars Trace Gas Orbiter, which studies the air around Mars. The gas, which is also seen in volcanic areas on Earth, was found in the same place as these long cracks in the ground.

The main reason for this finding is that there may still be magma—hot, melted rock—under the surface of Mars. When magma comes closer to the surface, gases like hydrogen chloride can move upwards and escape into the air through cracks. The gas also appears more in the early summer on Mars, which may be because ice covering the cracks melts in warmer weather and lets the gas out.

Because of this discovery, scientists now think Mars may still have some underground volcanic activity. However, they do not have proof that Mars’s volcanoes are active right now. They need more studies and data to understand if volcanoes are still working beneath the planet’s surface.