One of the most dramatic features in the entire Solar System is Olympus Mons on Mars. It’s the tallest known volcano and mountain in the Solar System, towering 27 kilometers above the surrounding plains, and covering a total area of 550 kilometers across.
Just as a comparison, the tallest volcano on Earth is Mauna Kea; Olympus Mons is 2.6 times as large. And it’s three times taller than Mount Everest above sea level.
If human travelers actually get to Mars, they would probably want to stand on the surface of Olympus Mons and look around, but they might be surprised to know it’s not a very dramatic view. The volcano is so tall, and so wide that you wouldn’t be able to see the top of the mountain from any point on its flanks. Mars is also a much smaller world than Earth, so its horizon is only a few kilometers away.
If you were actually standing at the top of Olympus Mons, you might be able to see the other side of the crater-like caldera that stretches about 80 kilometers across, and drops down 3 kilometers. Now that would be a dramatic view.
Scientists think that Olympus Mons was able to get so large over millions of years because Mars lacks active plate tectonics like we have here on Earth. A hotspot was able to form, and grow over time, releasing more and more magma.
Based on crater counts, some regions of Olympus Mons are as young as 2 million years old. This means that the shield volcano could very well still be undergoing active volcanic activity. We might be able to see more eruptions in the future.
Olympus Mons is part of the Tharsis bulge region of the Martian surface, which has many other large volcanic features. In fact, there are three other enormous shield volcanoes nearby: Arsia Mons, Pavonis Mons, and Ascraeus Mons; each of which would take the prize for the largest volcano in the Solar System if it weren’t for Olympus Mons.
Volcano world has more information on Olympus Mons, and the other Mars volcanoes. And Exploring Mars has a page on Olympus Mons.
Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.