Mount Everest Doesn’t Even Make the Top 10: The Tallest Mountains in the Solar System

Why the Tallest Mountains in the Solar System Dwarf Anything on Earth

When it comes to the tallest mountains in the Solar System, most people start with Mount Everest, but that’s the wrong planet entirely. Measured from base to summit, Everest reaches 29,032 feet above sea level, which doesn’t even earn it a place in the top ten. However, Mauna Kea is, in fact, the tallest mountain on Earth, rising more than 33,500 feet from base to summit. What is even more surprising is the mountains that stand taller still; peaks scattered across moons, asteroids, and planets throughout our Solar System.

• Related: Brain Post: 17 Interesting Facts About Mount Everest

As the tallest volcano in the Solar System, Olympus Mons on Mars stands approximately 72,000 feet high, two and a half times the elevation of Mount Everest above sea level, and is commonly cited as the tallest discovered peak in our solar system. It is also Mars’s tallest planetary mountain and is approximately tied with Rheasilvia for the title of tallest mountain discovered anywhere in the Solar System. A dormant shield volcano (not extinct, as recent geological evidence suggests lava flows as young as 25 million years ago), Olympus Mons has a base spanning 374 miles, roughly the size of the entire state of Arizona. If you placed it over Europe, it would cover France. Its summit pokes above Mars’s thin atmosphere entirely, meaning a hiker reaching the top would technically be stepping into space.

Rheasilvia is located on the asteroid Vesta and sits at the centre of a massive impact crater. It was discovered by the Hubble Space Telescope in 1997 and studied in detail by NASA’s Dawn spacecraft from 2011. Rheasilvia is approximately 314 miles in diameter, making up roughly 90% of Vesta’s own diameter. The central peak rises between 62,000 and 72,000 feet from the crater floor, potentially edging out Olympus Mons for the title of tallest single mountain in the Solar System. Scientists believe it formed roughly one billion years ago when another asteroid slammed into Vesta’s south pole.

How Scientists Measure Mountains on Other Worlds

Unlike on Earth, where mountain height is measured from sea level, there are no oceans on Mars, Io, or Vesta to serve as a baseline. Scientists instead measure from a reference datum, a mathematically defined average surface level for each body. This means that heights in the list below reflect a mix of local relief (base-to-peak) and datum elevation, depending on the source, and small variations in figures across different sources are normal. Where ranges are given, both are scientifically defensible.

The Complete Ranking: Tallest Mountains in the Solar System #3–#9

#10 Oberon Peak

• Location: Oberon, Moon of Uranus
• Height: ~36,000 feet

Detected in Voyager 2 imagery near Oberon’s south-eastern limb, this peak is believed to be the central feature of a large impact basin approximately 233 miles wide. It remains one of the least-studied mountains on this list due to the limited data from Voyager’s single flyby.

#9 Ionian Mons

• Location: Io, Moon of Jupiter
• Height: ~41,700 feet

One of many mountains on Jupiter’s volcanically hyperactive moon Io, Ionian Mons forms through a process unique in the Solar System, indirect volcanism, where sulphur-heavy material is constantly resurfacing the moon, compressing older rock beneath into rising mountain structures.

#8 Elysium Mons

• Location: Mars
• Height: ~41,300 feet (local relief); ~46,300 feet above Martian datum

The tallest peak in Mars’s Elysium volcanic province. Though dwarfed by the giants of Tharsis, Elysium Mons would still tower over any mountain on Earth.

#7 Pavonis Mons

• Location: Mars
• Height: ~28,500 feet (local relief); ~46,000 feet above Martian datum

The middle member of the Tharsis Montes chain, flanked by Ascraeus Mons to the north and Arsia Mons to the south. Pavonis Mons sits almost exactly on the Martian equator.

#6 Arsia Mons

• Location: Mars
• Height: ~38,400 feet (local relief); ~54,800 feet above Martian datum

The southernmost of the three Tharsis Montes, Arsia Mons, is the youngest of the trio in geological terms and has a summit caldera 68 miles across. After Olympus Mons, it is the largest volcano by volume in the Solar System, roughly 30 times the volume of Mauna Loa.

#5 South Boösaule Mons

• Location: Io, Moon of Jupiter
• Height: 57,400–59,700 feet

The tallest mountain on Io and one of the most striking in the Solar System. South Boösaule is not a volcano but a tectonic massif, a block of crust forced upward by the constant compression of Io’s surface under relentless gravitational kneading from Jupiter. The distance from Earth to Io is roughly 400 million miles, yet Io’s volcanoes are powerful enough to be detected from Earth-based telescopes. On the mountain’s south-east side, a cliff face drops approximately 49,000 feet in near-vertical relief.

#4 Ascraeus Mons

• Location: Mars
• Height: ~49,000 feet (local relief); ~59,700 feet above Martian datum

The tallest and northernmost of the three Tharsis Montes. Ascraeus Mons is 298 miles in diameter and, when measured from the Martian datum, rivals South Boösaule Mons for third place on this list. Its flanks are unusually shallow, with an average slope of just 7°, meaning that, despite its staggering height, a climber ascending it would experience something more like a very long hill than a dramatic peak.

#3 The Equatorial Ridge, Iapetus (Saturn’s Moon)

• Location: Iapetus
• Height: up to 65,600 feet

The Equatorial Ridge on Saturn’s moon Iapetus is the third-tallest mountain structure in the Solar System, reaching up to 65,600 feet in height and spanning more than 75% of the moon’s entire equatorial circumference. Discovered by the Cassini spacecraft in 2004, it is perfectly straight, sits exactly on the equator, makes up approximately 0.1% of Iapetus’s total mass, and its origin remains one of the great mysteries of planetary science. If you like ridgelines, this is the ridge.

Olympus Mons and the Equatorial Ridge: The Top Two

#2 Rheasilvia Central Peak (Vesta)

• Location: Vesta Asteroid, Asteroid Belt (between Mars and Jupiter)
• Height: 62,000–72,000 feet above crater floor

As detailed above, Rheasilvia’s central peak could be the tallest mountain in the Solar System, though the measurement debate with Olympus Mons is genuine and unresolved. What is not debated is the scale: rising to 72,000 feet from the crater floor inside a basin nearly the full width of Vesta itself, it is one of the most extraordinary geological features anywhere we have explored.

#1 Olympus Mons

• Location: Mars
• Height: ~72,000 feet above datum; up to ~85,300 feet local relief above surrounding plains

Already covered above, Olympus Mons is the undisputed tallest volcano in the Solar System and the most dramatic single peak on Mars. It sits on the same volcanic bulge as the Tharsis Montes (Pavonis Mons, Arsia Mons, and Ascraeus Mons), three volcanoes that are themselves larger than anything on Earth. The lack of tectonic plate movement on Mars means magma pools in one place indefinitely, allowing Olympus Mons to grow to a scale impossible on our own planet.

Could You Actually Ski the Tallest Mountains in the Solar System?

It is hard to believe that the tallest mountain on Earth is nothing compared to the astounding peaks that exist beyond it. If placed on the continent of North America, Olympus Mons would easily cover the entire state of Arizona. Yet, as mountaineers continuously tackle the next highest peak on Earth, does the thought ever cross their minds: the amount of vertical one could get skiing a peak two and a half times the height of Mount Everest?