Jupiter

This gas giant is the largest planet in the Sol System.

See

Atmospheric Composition
Jupiter's atmosphere is primarily composed of Hydrogen with some Helium.

Io
Thanks to tidal heating, Io experiences extreme geologic activity, making it the driest and most volcanically active object in the Sol System.

Europa
Europa's icy surface makes it one of the most reflective moons in the Sol System.

Ganymede
Ganymede is the Sol System's largest moon and the only one with a magnetosphere. It is bigger than Mercury and only slightly smaller than Mars.

Callisto
The tidally locked surface of Callisto is the oldest and most heavily cratered in Sol.