Saturn

Saturn is a massive gas giant best known for its spectacular ring system, which is composed of billions of icy particles ranging in size from dust grains to house-sized boulders. The rings stretch over 280,000 km across but are only about 10 meters thick on average.

Like Jupiter, Saturn’s atmosphere is made mostly of hydrogen and helium. It has strong winds and massive storms, including the famous hexagon-shaped jet stream at its north pole—one of the strangest atmospheric patterns in the Solar System.

Saturn also has over 145 moons, more than any other planet. One moon in particular, Titan, is one of the most Earth-like worlds ever discovered. It has a thick nitrogen-rich atmosphere and lakes made of liquid methane and ethane. Another moon, Enceladus, ejects plumes of water vapor from its south pole, hinting at a subsurface ocean that may host life.

Despite its size, Saturn is the least dense planet—it would float in water (if you had a bathtub big enough).