The Planets episode 4 – Life Beyond the Sun: Saturn


The Planets episode 4 – Life Beyond the Sun: Saturn is the jewel of the solar system, the most seductive of all the planets, but as Professor Brian Cox reveals – it wasn’t born that way.



Raised in the freezing outer reaches of the solar system, Saturn began life as a strange planet of rock and ice. Born outside the snow line, with an abundance of building materials, it soon grew to dwarf the Earth, drawing in colossal amounts of the hydrogen and helium that permeated the early solar system. In time Saturn was transformed into a gas giant, ring-less and similar looking to its great rival, Jupiter. As the gas giant grew, its original rocky form was lost forever, becoming part of the planet’s core, where temperatures are hotter than the surface of the sun, and pressures so intense that carbon there falls as diamond rain.


The Planets episode 4 – Life Beyond the Sun: Saturn


Saturn’s core isn’t the only part of it to change over time. As Nasa’s Cassini probe has discovered, the planet remained ring-less most of its life – until a fateful encounter changed everything. Less than a hundred million years ago, one of Saturn’s ice moons was drawn too close to the planet. In a truly cataclysmic event the entire moon was destroyed and the rings where born.

But Saturn’s true beauty may have remained hidden forever if it wasn’t for the decision to send Cassini on a risky close encounter with another moon, Enceladus. There we discovered an ocean with similar conditions to places on Earth where life thrives. Way out, far beyond the Sun, hydrothermal vents have been found, the very same habitat that we think life here on Earth may have got its start.


The Planets episode 4 – Life Beyond the Sun

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. It has only one-eighth the average density of Earth, but with its larger volume Saturn is over 95 times more massive. Saturn is named after the Roman god of agriculture; its astronomical symbol represents the god’s sickle.

Saturn’s interior is probably composed of a core of iron–nickel and rock (silicon and oxygen compounds). This core is surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and finally a gaseous outer layer. Saturn has a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn’s planetary magnetic field, which is weaker than Earth’s, but has a magnetic moment 580 times that of Earth due to Saturn’s larger size. Saturn’s magnetic field strength is around one-twentieth of Jupiter’s. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h

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