Saturn
Cassini, 2009, during Saturn’s equinox — the rings edge-on, casting a thin shadow.
Saturn’s rings are simultaneously the most iconic structure in the solar system and, geologically speaking, surprisingly young — likely formed between 10 and 100 million years ago, when dinosaurs still walked on Earth. They are also disappearing: ring material is raining into Saturn’s atmosphere at a rate that would drain them completely within 100 million years.
The rings
The rings span 282,000 km but are on average only 10–20 metres thick — thinner, relative to their width, than a sheet of paper. They are almost entirely water ice, with trace rocky material.
| Ring | Distance from centre | Width |
|---|---|---|
| D | 67,000–74,500 km | 7,500 km |
| C | 74,500–92,000 km | 17,500 km |
| B | 92,000–117,500 km | 25,500 km |
| A | 122,200–136,800 km | 14,600 km |
| F | 140,200 km | narrow, braided |
The Cassini Division (between B and A) is not empty — it contains diffuse ring material, cleared into a resonance pattern by the moon Mimas.
Titan
Saturn’s largest moon has a thick nitrogen atmosphere, lakes of liquid methane and ethane at its poles, and a methane cycle that mirrors Earth’s water cycle. Dragonfly — a rotorcraft lander — is scheduled to arrive in 2034 to fly between sites in Titan’s dune fields and craters.