Geography of Mars Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major Planum. The shield volcano, Olympus Mons ("Mount Olympus"), rises 22 km above the surrounding volcanic plains, and is the highest known mountain on any planet in the solar system. It is in a vast upland region called Tharsis, which contains several large volcanos. See list of mountains on Mars. The Tharsis region of Mars also has the solar system's largest canyon system, Valles Marineris or the "Mariner Valley", which is 4,000 km long and 7 km deep. Mars is also scarred by countless impact craters. The largest of
Ahuna Mons on the opposite side of Ceres, fracturing the outer layers of the area and facilitating the movement of high viscosity cryovolcanic magma (consisting of muddy water ice softened by its content of salts) that was then extruded onto the surface. Crater counts suggest that formation of the mountain continued into the last several hundred million years, making this a relatively young geological feature. Ahuna Mons Ahuna Mons is the largest mountain on the dwarf planet and asteroid Ceres. It protrudes above otherwise smooth terrain, it is not an impact feature, and it appears to be the only mountain of its