Planets in our solar system are grouped based on their formation and physical characteristics. This classification system helps distinguish between worlds close to the Sun and those in the distant, colder reaches of space. To determine Saturn’s place, scientists examine the distinct criteria used to sort the solar system’s eight major planets. Physical properties, such as density and composition, provide the necessary clues.
How Planets Are Classified
Planetary bodies in our solar system are sorted into two major groups: Terrestrial planets and Jovian planets. This distinction is based on composition, size, and location relative to the Sun.
The Terrestrial planets (Mercury, Venus, Earth, and Mars) are characterized by high density and solid surfaces, composed mainly of silicates and metals. These smaller worlds formed closer to the Sun where high temperatures prevented lighter elements like hydrogen and helium from accumulating. Consequently, they possess thin atmospheres and few, if any, moons.
The Jovian planets, named after Jupiter, are massive worlds with low densities. They formed in the outer solar system, where cooler temperatures allowed them to retain vast quantities of the lightest elements, predominantly hydrogen and helium. These planets lack a defined solid surface, instead featuring deep atmospheres that transition to liquid interiors under immense pressure.
The Unique Structure of Saturn
Applying these criteria reveals Saturn’s fundamental nature, dominated by a deep, gaseous composition. Saturn is composed of approximately 96% hydrogen and 3% helium, along with trace amounts of other gases. This dominance of light elements gives Saturn the lowest average density of any planet in the solar system, making it less dense than water.
The planet lacks a true surface; the atmosphere gradually becomes denser as pressure increases with depth. This extreme pressure transforms the hydrogen into a liquid metallic state, which is the source of the planet’s magnetic field. Deep within this liquid interior lies a small, dense core composed of rock and ice, estimated to be between 9 and 22 times the mass of Earth.
Saturn’s rapid rotation rate, completing a day in just over ten and a half hours, causes an equatorial bulge. The planet’s famous ring system consists of countless chunks of water ice and rocky material orbiting the planet.
Saturn’s Placement in the Solar System
Based on its physical properties, Saturn is classified as a Jovian planet, or gas giant. Its composition of light elements, low density, and lack of a solid surface place it firmly in this category.
Saturn is the sixth planet from the Sun, occupying the outer solar system alongside the other Jovian worlds: Jupiter, Uranus, and Neptune. These massive, low-density giants stand in contrast to the small, high-density, rock-and-metal Terrestrial planets of the inner solar system.