The Red Planet, Mars (main); Olympus Mons, the tallest volcano in the solar system (top right); and Alba Mons, the largest volcano in the solar system, where evidence of dormant volcanism was found (bottom right). (Image credit: NASA/ Robert Lea)

Scientists have long suspected that Mars is geologically "dead," but new spacecraft observations suggest the Red Planet's volcanoes are merely sleeping.

That means that Olympus Mons , the extinct Martian volcano that at around 16 miles (26 kilometers) above the surrounding Martian plains is the largest mountain in the solar system , may in fact be a slumbering giant.

The observations were made with the European Space Agency (ESA) mission ExoMars Trace Gas Orbiter (TGO) as it studied volcanic fissures along the Alba Mons region of the Red Planet. Alba Mons is in the Tharsis region of Mars, the same area that is home to Olympus Mons.…