[Jack Black]

Juptier's moons are much smaller than Earth. The largest ones have a diameter around 1/8 that of Earth, meaning they are 1/512 the size of Earth.

I love people who know these formulas off the top of their head. Size in the above example = volume? Unless the planet is hollow the most interesting measure is surface area. What is the surface area of a planet 1/8 the diameter of earth? This tells us how much space their is to ranch, mine and ride ATVs on!! Earth = 1 Earth Surface Area. How big is Mars? Please show your work so I can learn the formulas. Thanks.

[Hermann the Cherusker]

I believe surface area is 4/3 * PI * radius cubed. I hope I'm not confusing formulas here.

[Hermann the Cherusker]

Sorry, I am confusing them.

Spherical Volume is 4/3 * PI * radius cubed

Spherical Surface is 4 * PI * radius squared

Diameter of:
Io - 1942 miles
Europa - 2000 miles
Ganymede - 3400 miles
Callisto - 3000 miles

Earth - 7926 miles

The Jovian moons are bigger than I recalled. The Earth has 5 times the surface of Ganymede, the largest, and 13 times the volume.