Here's a fact that blows my mind: Jupiter has no hard surface.
We're so used to standing on hard ground on our planet, seeing the sky (atmosphere) above us and seeing the sea (hydrosphere).
But Jupiter is a gas giant - it has no hard distinctions between land, air and sea. There are outer layers of gas, and as you go beneath the surface, thousands of miles down into the planet, the gas gradually becomes compressed or becomes liquid (don't think astronomers are sure).
So, humans can't stand on Jupiter (if our technology allows us to reach the planet).