Saturn

The second-largest planet in the Solar System, and the second of the gas giants. Learn more about the ringed planet here!

Formation

The formation of the gas giants is controversial and shrouded in mystery. Models of a young Saturn suggest that the core of the planet formed in the Solar nebula before the ignition of the Sun, gaining a core of up to 15 Solar masses. As the core gathered mass, it gathered the gases that made up its atmosphere to create the gas giant observed today. Another model suggests that Saturn formed close to the Sun, a little further from the present-day Mars orbit, and over time formed a resonance with the orbit of Jupiter, pushing the orbits of the two gas giants back to their present-day positions. As the two gas giants migrated outwards, Saturn would have gathered large quantities of gas to form its atmosphere. Still yet other models suggest that Saturn formed further out compared to its present orbit, near the present-day Neptune orbit, and migrated inwards. Much is still yet to be learned about the formation of the gas giants and Saturn.

Composition

The composition of Saturn is thought to be similar to the composition of the young Solar nebula. Around 75% of the ringed planet is composed of hydrogen, 24% helium, and 1% other elements such as oxygen, nitrogen, carbon, and sulfur. The atmosphere of Saturn is slightly different, with there being more hydrogen in the atmosphere compared to the total mass of the planet thanks to less helium being found in the atmosphere. This implies that the helium in the atmosphere is sinking into the planet, depleting the atmosphere’s helium.

Structure

As a gas giant, Saturn has a structure that is more similar to that of the Sun than Earth. The core of Saturn is probably solid, in contrast to Jupiter which could have a more diffuse core. Surrounding the core is believed to be a large layer of metallic hydrogen, with electrical currents flowing and creating the strong magnetic field surrounding Saturn. Above this layer of metallic hydrogen is liquid hydrogen, with possible helium and neon droplets falling to the middle of the planet. Finally at the outermost edge of the planet is the atmosphere.

Atmosphere

The atmosphere of Saturn is made up of mostly hydrogen, with water ice and ammonia clouds. These clouds are formed in prominent bands that circle the planet from North to South. Giant storms form periodically on Saturn, though not as often as the storms produced by Jupiter. At the poles, large hexagonal storms form, with the Southern hexagonal storm being the only example in the Solar System of a warm polar vortex, a whole one hundred and twenty degrees Fahrenheit warmer.

Magnetic Field

The magnetic field of Saturn is slightly weaker than that of Earth’s magnetic field. Believed to be caused by the metallic hydrogen layer located within the planet, the magnetic field causes auroras on Saturn’s poles. The magnetic field stretches from 19 Saturnian radii towards the Sun, with the tail stretching out further behind the planet. The largest moon of Saturn, Titan, is located inside the magnetic field, and is  protected from Solar radiation reaching the atmosphere.

Planetary Rings

Saturn has the largest planetary ring system out of the planets in the Solar System. The origins of the rings of Saturn are not fully understood, with some theories suggesting that a moon was destroyed and the debris created the rings, or the material was left over from the initial formation of Saturn and formed into the rings. The rings are mostly composed of water ice, with the material formed of objects on the order between micrometers to meters. The rings of Saturn are labelled by letters, A through G, and are named after the order of discovery, causing the order to not be alphabetical as you move away from the Saturnian atmosphere.

Satellites

Pioneer 11 was the first satellite to visit Saturn in a flyby. The rings of Saturn were seen from up close for the first time, allowing the discovery of the F ring and finding that the gaps and divisions have some material in them, not none as expected.

Voyager 1 and Voyager 2 were the next satellites to fly by Saturn. Voyager 1 took high-resolution images of Saturn for the first time, detailing the surface of some moons. Titan was observed in the visible spectrum as well, but the atmosphere is too dense to observe the surface. Voyager 2 was also able to take high-resolution images of Saturn, revealing changes in the atmosphere since Voyager 1 visited a year earlier. The images taken by Voyager 2 revealed new moons of Saturn, while also discovering previously unknown gaps in the ring system.

Cassini is the most recent satellite to visit the Saturnian system, being inserted into orbit for continuous monitoring of the planet. Cassini was able to observe weather patterns on Saturn, along with detecting lightning in the atmosphere. New, smaller rings were discovered thanks to the images taken by Cassini. The satellite was also equipped with the Huygens probe, designed to land on the surface of Titan. The Huygens probe was launched to the surface, revealing details of the material up close. Cassini was able to view through the atmosphere of Titan, revealing hydrocarbon lakes on the surface, up to the size of seas on Earth. The moon Enceladus was revealed to have water geysers fueled by water beneath the icy surface. Upon completion of its mission, Cassini performed a grand finale by weaving through Saturn’s rings, eventually falling into the atmosphere.