An enormous plume of magma over a thousand miles across is slowly but steadily rising underneath Mars' Tharsis volcanic region and could one day provoke a mighty eruption from the solar system's tallest mountain, Olympus Mons.
At 13.6 miles (21.9 kilometers) tall, Olympus Mons climbs so high into the Martian sky that its caldera pokes out of Mars' atmosphere and into space. Olympus Mons is joined by three other large volcanoes in the Tharsis region: Ascraeus Mons, Arsia Mons and Pavonis Mons. All of these volcanoes have been dormant for millions of years, but that could be changing, new research suggests.
