Saturn, also known as the Ringed Planet, is the sixth planet from the Sun and the second-largest planet in the Solar System by diameter and mass, following Jupiter.
Saturn is a gas giant with an average radius about nine times that of Earth. Although its mass is 95 times that of Earth, its volume is over 763 times greater, resulting in an average density that is only one-eighth that of Earth.
Structure of Saturn
The internal structure of Saturn is believed to consist of an iron, nickel, and rock core (composed of silicon and oxygen compounds), surrounded by a thick layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and an upper atmosphere.
The primary component of the planet is hydrogen, which becomes a non-ideal liquid at high densities above 0.01 g/cm³. This density is achieved at the radius containing 99.9% of Saturn’s mass. Temperature, pressure, and density increase gradually towards the core, and at deeper layers within the planet, hydrogen transitions into a metallic phase.
Actual color photo of Saturn, taken by the Cassini spacecraft.
Atmosphere of Saturn
The outer atmosphere of Saturn contains 96.3% hydrogen molecules and 3.25% helium. The proportion of helium is significantly lower than its presence in the Sun. Scientists are still uncertain about the exact amount of heavier elements in the planet’s atmosphere, but they assume that the ratios of these elements are consistent with their primordial ratios from the formation of the Solar System.
Clouds on Saturn
Saturn’s atmosphere appears with color bands similar to those of Jupiter, but the bands on Saturn are fainter and broader at the planet’s equator. Scientists use similar naming conventions for these bands as they do for Jupiter. The faint cloud bands of Saturn were not discovered until the Voyager spacecraft flew by the planet in the 1980s.
Magnetosphere of Saturn
Saturn has a simple magnetic field that resembles a dipole. Its intensity at the equator is -0.21 gauss (21 µT), approximately one-twelfth the intensity of the magnetic field surrounding Jupiter and slightly weaker than the magnetic field of Earth. Therefore, Saturn has a significantly smaller magnetosphere compared to that of Jupiter.
Orbit of Saturn
The average distance between Saturn and the Sun is over 1.4 billion kilometers (9 AU). With an average orbital speed of 9.69 km/s, Saturn takes 10,759 Earth days (about 29.5 years) to complete one orbit around the Sun. Saturn’s elliptical orbit is tilted about 2.48° relative to the orbital plane of Earth.
Planetary Rings
The rings of Saturn (captured by the Cassini orbiter in 2007) are the largest planetary rings in the Solar System.
Saturn is perhaps best known for its stunning ring system, which creates its most striking visual appearance.
The rings extend from 6,630 km to 120,700 km above Saturn’s equator, with an average thickness of about 20 meters, composed of up to 93% water ice, some tholins, and 7% amorphous carbon.
Natural Satellites of Saturn
As of now, Saturn has at least 62 moons, 53 of which have been named. Titan is Saturn’s largest moon, accounting for more than 90% of the total mass of all objects orbiting Saturn, including the rings.
Exploration of Saturn
Pioneer 11 was the first spacecraft to fly by Saturn in September 1979, coming within 20,000 km of the planet’s cloud tops. The images sent back included the planet and some of its moons, although the resolution was too low to discern surface details. The spacecraft also studied Saturn’s rings, discovering the thin F ring and dark gaps in the rings that lit up when viewed under a large phase angle toward the Sun, indicating that these dark gaps contained small dust particles that scattered light. Additionally, Pioneer 11 measured Titan’s temperature and indicated that this moon was too cold to support life.
Saturn obscuring the Sun, viewed from the Cassini spacecraft.
In November 1980, Voyager 1 arrived at the Saturn system. It sent back high-resolution images of the planet, its rings, and its moons. Surface details of several moons were observed for the first time.
A year later, in August 1981, Voyager 2 continued to fly by and study this planetary system. More close-up images of Saturn’s moons were sent back to Earth, along with additional data on atmospheric changes and the planetary ring system.
On July 1, 2004, the Cassini-Huygens spacecraft conducted trajectory adjustments and entered orbit around Saturn. Before entering orbit, Cassini conducted studies of this planetary system. In June 2004, it performed a close flyby of the moon Phoebe, sending back high-resolution data and images of this moon to mission control.
