I think it's stretching the definition of "surface" to include the rings of Saturn. Maybe another "7 Orbital Wonders" is worth doing?

7 Ices at the pole of Mercury - The most extreme temperature gradient of any rocky planet
6 Vallis Marineris - The largest chasm in the Solar System
5 The Great Red Spot of Jupiter - Largest organised storm system
4 The Plate Tectonic System of Earth - Largest organised Tectonic system
3 The surface Temperature of Venus - Most extreme Greenhouse on a rocky planet
2 Mons Olympus (Mars) - Largest Volcano in the solar system
1 The Oceans of Earth - Most remarkable volatile occurence in the Solar system