Tharsis Montes Tharsis Montes The Tharsis Montes are three large shield volcanoes in the Tharsis region of the planet Mars. From north to south, the volcanoes are Ascraeus Mons, Pavonis Mons and Arsia Mons. Mons (plural "montes") is the Latin word for mountain; it is a descriptor term used in astrogeology for mountainous features in the Solar System. The three Tharsis Montes volcanoes are enormous by terrestrial standards, ranging in diameter from (Pavonis Mons) to (Arsia Mons). Ascraeus Mons is the tallest with a summit elevation of over , or base-to-peak. For comparison, the largest volcano on Earth, Mauna Loa in Hawaii,
Olympus Mons unaware of standing on a very high mountain, as the slope of the volcano would extend far beyond the horizon, a mere 3 kilometers away. The typical atmospheric pressure at the top of Olympus Mons is 72 pascals, about 12% of the average Martian surface pressure of 600 pascals. Both are exceedingly low by terrestrial standards; by comparison, the atmospheric pressure at the summit of Mount Everest is 32,000 pascals, or about 32% of Earth's sea level pressure. Even so, high-altitude orographic clouds frequently drift over the Olympus Mons summit, and airborne Martian dust is still present. Although the average