Author: Fraser Cain

Saturn couldn’t be more different from Earth; it’s mostly made of hydrogen and helium and has nearly 100 times more mass. And those rings…

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

But Saturn’s axis is tilted, just like Earth. While Earth’s axis is tilted at an angle of 23.4°, Saturn’s tilt is 26.7°. That’s pretty close.

And just like Earth, Saturn’s axial tilt gives the planet seasons. In fact, we can see Saturn’s tilt by the position of the rings. When Saturn’s northern hemisphere is experiencing summer, we can see the rings at their widest point. And then, as Saturn works its way through its 30-year orbit around the Sun, the angle to the rings decreases until they’re almost invisible – just a line through the planet.

The changing seasons on Saturn also affect the planet’s weather patterns. NASA’s Voyager spacecraft originally clocked wind speeds near Saturn’s equator at nearly 1,500 km/h. But when Cassini showed up 15 years later, they’d slowed down to only 1,100 km/h.

Here’s an article from Universe Today about long term changes on Saturn, and three views of Saturn over a long period of time.

Here’s a nice photograph from Astronomy Picture of the Day of Saturn, and another captured by Cassini, showing the planet’s southern hemisphere being illuminated.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Saturn is easily visible with the unaided eye, so it’s hard to say when the planet was first discovered. The Romans named the planet after Saturnus, the god of the harvest – it’s the same as the Greek god Kronos.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Nobody realized the planet had rings until Galileo first turned his rudimentary telescope on the planet in 1610. Of course, Galileo didn’t realize what he was looking at, and thought the rings were large moons on either side of the planet.

It wasn’t until Christian Huygens used a better telescope to see that they were actually rings. Huygens was also the first to discover Saturn’s largest moon Titan.

Jean-Domanique Cassini uncovered the gap in Saturn’s rings, later named the Cassini Division, and he was the first to see 4 more of Saturn’s moons: Iapetus, Rhea, Tethys, and Dione.

There weren’t many more major discoveries about Saturn until the spacecraft flybys in the 70s and 80s. NASA’s Pioneer 11 was the first spacecraft to visit Saturn, getting within 20,000 km of the planet’s cloud layers. It was followed by Voyager 1 in 1980, and Voyager 2 in August 1981.

It wasn’t until July 2004 that NASA’s Cassini spacecraft arrived at Saturn, and began the most detailed exploration of the system. Cassini has performed multiple flybys of many of Saturn’s moons, and sent back thousands of images of the planet and its moons. It has discovered 4 new moons, a new ring, and saw liquid hydrocarbon seas on Titan.

This article was published when Cassini had finished half its primary mission, and discusses many of the discoveries made so far, and another article when its primary mission was complete.

This article has a timeline of Saturn history, and more history from NASA.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Like the rest of the planets, Saturn formed from the solar nebula about 4.6 billion years ago. This solar nebula started out as a vast cloud of cold gas and dust which was disturbed somehow – perhaps by colliding with another cloud, or the shock wave from a supernova.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

The cloud compressed down, forming a protostar in the center, surround by a flattened disk of material. The inner part of this disk contained more heavier elements, and formed the terrestrial planets, while the outer region was cold enough for ices to remain intact.

These ices came together, forming larger and larger planetesimals. And these planetesimals collided together, merging into planets. At some point in Saturn’s early history, a moon roughly 300 km across might have been torn apart to create the rings that circle the planet today.

Since Saturn was smaller than Jupiter, it cooled down more quickly. Astronomers think that once its outer atmosphere reached about 15 K, helium condensed into droplets that fell towards its core. The friction from these droplets heated up the planet to the point that it gives off roughly 2.3 times the amount of energy it receives from the Sun.

Here’s an article from Universe Today about how the gas giant planets might have consumed their moons early on, and another article about how gas giant planets might form around other stars.

Here’s an article about the formation of Saturn’s rings, and an article about what Saturn’s moons might tell scientists about planet formation.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Just like Jupiter, Saturn radiates out more energy that it draws in from the Sun. In fact, Saturn radiates 2.3 times more energy than it receives from the Sun.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

This has been a bit of a mystery to scientists. But the solution lies in the fact that Saturn’s atmosphere is relatively poor in helium, compared to Jupiter. Scientists think it cooled faster than Jupiter after initial formation, and then helium droplets formed when the temperature of the atmosphere dropped below 15 K. These droplets have been falling down into the core of Saturn, heating it up, and generating the heat.

When NASA’s Cassini first arrived at Saturn, the spacecraft detected lightning storms and radiation belts around the planet. It even found a brand new radiation belt located inside the rings of Saturn. The belts extend from about 139,000 km from Saturn’s center out to 362,000, and contain highly charged particles.

Here’s an article about Cassini finding the radiation belts around Saturn, and another about strange radio emissions coming from Saturn, related to the belts.

Here’s more information on the radiation belts, and a nice photograph from NASA.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Jupiter is well known for the storms that rage across its upper atmosphere, especially the Great Red Spot. But Saturn has storms too. They’re not as large, intense or large lived, but compared to Earth, they’re enormous. And Saturn has one of the big mysteries in the Solar System; a hexagon-shaped storms at its poles.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Winds blow hard on Saturn. The highest velocities are near the equator, where easterly blowing winds can reach speeds of 1,800 km/h. The wind speeds drop off as you travel towards the poles.

Like Jupiter, storms can appear in the bands that circle the planet. One of the largest of these was the Great White Spot, observed by the Hubble Space Telescope in 1990. These storms seem to appear once every year on Saturn (once every 30 Earth years).

NASA’s Cassini spacecraft discovered static hexagonal storm circling around Saturn’s north pole, including a clearly defined eyewall – just like a hurricane. Each side on the northern polar hexagon is approximately 13,800 km long, and the whole structure rotates once every 10 hours and 39 minutes; the same as a day on Saturn.

Here’s an article about a time when Cassini tracked a long-lived lightning storm on Saturn, and another about the strange “Dragon Storm” seen in the planet’s southern hemisphere.

Here’s an article about the northern hexagonal storm from MSNBC, and Astronomy Picture of the Day has an image of storm alley on Saturn.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

It’s hard to imagine a planet less hospitable for life than Saturn. The planet is comprised almost entirely hydrogen and helium, with only trace amounts of water ice in its lower cloud deck. Temperatures at the top of the clouds can dip down to -150 C.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Temperatures do get warmer as you descend into Saturn’s atmosphere, but the pressures increase too. When temperatures are warm enough to have liquid water, the pressure of the atmosphere is the same as several kilometers beneath the ocean on Earth.

To find life, scientists will want to take a good look at Saturn’s moons. They’re comprised of significant amounts of water ice, and their gravitational interaction with Saturn probably keeps their interiors warm. Saturn’s moon Enceladus is known to have geysers of water erupting from its southern pole. It’s possible that it has vast reserves of superheated water beneath an ice crust.

And Saturn’s moon Titan has lakes and seas of hydrocarbons, thought to be the precursors of life. In fact, scientists think that Titan is very similar in composition to the Earth’s early history.

Hydrocarbons have even been detected across the surface of Saturn’s moon Hyperion.

There might not be life on Saturn, but there are enough intriguing locations to explore around the ringed planet to keep astronomers busy for years.

Here’s an article about exotic life that could live on Titan, and another that dismisses the possibility that there’s life on Enceladus.

This is an article from the Guardian about the possibility of life on Enceladus, and hydrocarbons on Hyperion.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Saturn formed with the rest of the planets 4.6 billion years ago, out of a spinning disk of gas and dust. This dust collapsed down to form the Sun, and planets formed out of the disk around it. This is why all of the planets orbit the Sun in the same direction.

That’s the easy question.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

The more complicated question is, how old are Saturn’s rings? Some parts might be almost as old as the Solar System, but others are being continuously refreshed. The primary theory for the formation of Saturn’s Rings is that a 300 km moon was torn apart by Saturn’s gravity into the ring system that we see today. But that probably happened more than 4 billion years old.

But Saturn’s rings are bright, and almost made of pure water ice. Since infalling dust should have darkened the rings, they might be as young as 100 million years old. Or perhaps they are ancient, but regular collisions between ring objects keep them looking fresh and new.

One interesting note. Astronomers think that the composition of Saturn – 88% hydrogen and 11% helium with other trace elements – almost exactly matches the composition of the early solar nebula. Saturn is like a miniature version of the Solar System.

Here’s an article from Universe Today that discusses how Saturn’s rings could be as old as the Solar System, and another article about how gas giant planets might have consumed many of their moons early on in their history.

Ask an Astronomer has another answer to this question, and another look at the age of the rings from Geology.com.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Saturn is almost entirely hydrogen and helium, but it does have trace amounts of other chemicals, including water. When we look at Saturn, we’re actually seeing the upper cloud tops of Saturn’s atmosphere. These are made of frozen crystals of ammonia.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

But beneath this upper cloud layer, astronomers think there’s a lower cloud deck made of ammonium hydrosulfide and water. There is water, but not very much.

Once you get away from Saturn itself, though, the nearby area has plenty of water. Saturn’s rings are almost entirely made of water ice, in chunks ranging in size from dust to house-sized boulders.

And all of Saturn’s moons have large quantities of water ice. For example, Saturn’s moon Enceladus is thought to have a mantle rich in water ice, surrounding a silicate core. Geysers of water vapor were detected by NASA’s Cassini spacecraft, spraying out of cracks at Enceladus’ southern pole.

If you want to look for water at Saturn, don’t look at the planet itself, but there’s water all around it.

Here’s an article from Universe Today about the plume of water ice coming off of Enceladus, and how Saturn’s environment is driven by ice.

Here’s an article from NASA about the composition of ice at Saturn’s moon Rhea, and the discovery of liquid water on Enceladus.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.