The Massive Gas Giant That Naturally Floats

Saturn is the only planet in our solar system that is less dense than liquid water. Despite being 95 times more massive than Earth, its composition is so light and airy that it weighs only about 0.687 grams per cubic centimeter.

Most of the planet consists of hydrogen and helium. While the core is likely a dense mix of rock and ice, the vast majority of Saturn’s volume is occupied by gas layers that lack the tight molecular packing found on rocky planets. If you dropped it into a cosmic ocean, it would stay afloat while Earth would sink like a pebble.

This lack of density creates strange physics at the surface. Gravity on Saturn is surprisingly similar to Earth's because the planet’s mass is spread across such a gigantic area. You would feel almost normal standing on a platform there, provided you didn't fall through the clouds.

The planet is also spinning so fast that it has flattened itself out. It is noticeably wider at the equator than it is from top to bottom, a shape called an oblate spheroid. This rapid rotation actually makes the planet even less dense as centrifugal force pulls its gases outward.