Which planet in the solar system has the most extensive canyon?

The planet in the solar system with the most extensive canyon is Mars. The canyon, known as Valles Marineris, is located on the Martian equator and is over 4,000 km long, up to 200 km wide, and up to 7 km deep. To put that into perspective, Valles Marineris is over 3 times longer than the Grand Canyon in Arizona and over 20 times deeper in some places.

Scientists believe that Valles Marineris was formed by tectonic activity, where the Martian crust was pulled apart by the planet's interior. Some areas of the canyon show signs of erosion, suggesting that it was once filled with water. Today, Valles Marineris is a popular destination for space probes and rovers, as it provides a unique opportunity to study the geology and history of Mars.