The tallest mountain on any of the Solar System’s planets is Olympus Mons, a giant extinct volcano on Mars that is some 14 miles (or 21.9 kilometers) high. That’s about two and a half times the height of Mount Everest. This behemoth formed some 3 billion years ago when the Red Planet was peppered with volcanoes spewing vast quantities of magma across the Martian planes.
Since then, Mars has cooled and become much less active. Indeed, a common view among planetary geologists is that today there are no active volcanoes on Mars.
