Icy moons aren’t the only place in the Outer Solar System where ice takes center stage. Saturn’s rings are almost entirely composed of water ice, and are seen here in a mosaic of photos taken by NASA’s Cassini Spacecraft:
Saturn’s rings are formed from the debris of ancient moons that drifted too close to the planet, past an invisible barrier known as the Roche Limit, and were torn apart by Saturn’s gravitational tides (yes – dissipation of tidal energy is important here, too)! The rings do not spin around the planet entirely peacefully, either. Icy pillars rise up from the rings, visible only at the planet’s Equinox:
The conditions required to take this photo occur only once every 15 years… so mark your calendar for 2024, when the next sighting opportunity arises!
The rings also swirl with turbulence as pieces of debris collide and swarm around one another:
But the rings are not only places of turbulence and destruction: Cassini recently captured this image of the birth of a new moon amid the debris.
Saturn’s rings may be beautiful, but they certainly aren’t passive …and to fully understand their dynamics, we must understand the physics of ice!
For more cool images (pun intended), check out the Cassini Mission’s website.