Here's why:

* Olympus Mons: The largest volcano in the solar system, Olympus Mons, is located on Mars. It's a shield volcano, meaning it's very wide and has gentle slopes. It's three times taller than Mount Everest!

* Other Martian Volcanoes: Mars also has other large volcanoes like Ascraeus Mons, Pavonis Mons, and Arsia Mons.

While Venus also has volcanoes, they are not as prominent as those on Mars.