The Largest Volcano in the Solar System Is on Mars

Most people know Mount Everest as the tallest mountain on Earth, standing about 8.8 kilometers above sea level. It is an impressive achievement of nature. But on Mars, there is a volcano so enormous that Everest would look like a small hill standing next to it.

That volcano is called Olympus Mons. It stands about 22 kilometers tall and stretches roughly 600 kilometers across its base — wide enough to cover the entire country of France.

To understand just how tall Olympus Mons is, consider this: commercial airplanes typically cruise at an altitude of about 10 to 12 kilometers. Olympus Mons towers nearly twice as high as a cruising airplane.

Its slopes are so gradual, rising only a few degrees, that if you stood on the surface of Olympus Mons, you would not even realize you were on a volcano. The mountain is simply too wide and too flat for a person standing on it to see its full shape.

The answer lies in one key difference between Mars and Earth: tectonic plates. Earth's crust is divided into large moving plates. When a hotspot under the crust pushes magma upward, the plate slowly shifts away, spreading volcanic activity across a wide area over time.

Mars, however, has no tectonic plates. Its crust is a single, fixed shell. When a hotspot pushes magma upward on Mars, the crust stays in place. Lava piles up in exactly the same spot for billions of years, building a volcano of almost unimaginable scale.

Scientists believe Olympus Mons is currently dormant, meaning it is not erupting but is not considered completely extinct either. Some regions of the volcano show evidence of relatively recent lava flows — recent in geological terms, meaning within the last few million years.

Whether it could erupt again in the distant future remains an open question. Mars is a geologically active planet, and Olympus Mons may not have spoken its last word.

Olympus Mons is more than just a record-breaking mountain. It is a record of billions of years of Martian history, preserved in layers of ancient lava. By studying it, scientists hope to understand how the interior of Mars has evolved over time and what conditions on the young planet may have been like.

No human has ever set foot on Mars. But if one day an astronaut climbs Olympus Mons, they will be standing on the greatest mountain any human has ever touched — a volcano that makes Everest feel like a step on the porch.