From Saturn’s images, it is easy to think that the planet is as serene as it looks through a telescope.
Turns out it is not.
Temperatures on Saturn are not consistent and don’t change seasonally as they do on Earth. However, throughout the Saturnian year (29 Earth years), tiny storms and hurricanes occur in the planet’s atmosphere.
Every 30 Earth years or one Saturnian year, for example, a huge storm called the Great White Spot occurs that encircles the entire planet. This periodic storm is accompanied by flashes of lightning.
Moreover, there are also long-term features on Saturn, like the hexagonal cloud formation in the planet’s north pole.
How do we know all this? Well, many spacecraft have visited the planet and provided us with lots of information.
Let’s dig in.
Saturn’s Temperature
Saturn’s average temperature hovers around -218 °F (-138 °C). The planet’s maximum temperature of 21,000 °F (11,700 °C) is reached at the heart of its interior, the further outwards one travels from there, the cooler it becomes.
Orbiting 1.4 billion kilometers away from the Sun, Saturn radiates twice as much heat from its interior than it receives from the Sun. This has the curious effect of removing seasonality from Saturn’s weather.
On Earth, we are familiar with seasonal temperature changes: it is hotter during the summers and cooler during winters. However, although Earth and Saturn have similar axial tilts (Saturn’s is 27°, Earth’s 23.5°), Saturn does not experience noticeable temperature changes as it orbits the sun.
The stability in its weather is because the majority of heat that it receives comes not from the Sun, but itself.
How Much Warming Does Saturn Get From the Sun?
Saturn receives one percent as much sunlight as we get here on Earth.
However, Saturn radiates twice that amount into space, indicating that it has an active core that constantly generates heat.
Saturn’s Atmosphere
You might be aware that Saturn does not have a surface per se. It is made up of complex layers, which, if peeled like the layers of an onion, will reveal themselves.
Saturn’s atmosphere is primarily made of hydrogen, with about 18-25% helium, and 2% of other molecules in trace amounts. Get more detail on what Saturn’s atmosphere is made of.
What we see from Earth is the uppermost layer, which contains icy ammonia. It’s this chemical that gives Saturn a hazy yellow color. The ammonia is icy in nature because the molecules have risen so far from the core that the temperatures became cool enough for them to freeze.
Other molecules give the upper atmosphere shades of brown as well. Temperatures range from -280 °F (-173 °C) to -170 °F (-113 °C).
The second layer of atmosphere contains methane and water ice molecules. Temperatures here range from -127 °F (88 °C) to 26 °F (-3 °C).
From the third layer onward, the temperature increases to 134 °F (57 °C) until the core, where the temperature is 21,000 °F (11,700 °C).
Hexagon Cloud Formation
Saturn’s north pole features a unique, persistent cloud structure.
It is made up of jet streams traveling at speeds that reach 320 kilometers per hour. It is distinctly hexagonal in shape, 9,000 miles (14,500 km) long, and 18,000 miles (29,000 km) wide and resides at 78°N.
This “hexagon”, which was discovered by the Voyager spacecraft in 1981, does not shift in longitude: it has stayed in the same place since its discovery. What does change is its color. From 2012 to 2016, the cloud changed its color from blue to golden.
We don’t really know what caused this hexagon to form, and what forces in Saturn’s atmosphere are driving its existence. One leading theory suggests that atmospheric winds in the north pole lead to this formation and that the hexagon itself is suspended in air, hundreds of miles above the clouds.
Great White Spot
Every planet is subjected to storms, and Saturn is no different.
Once every 30 years, which is one Saturnian year, the gas giant experiences fierce storms triggered by cloud disturbances. Leading these storms in terms of size and strangeness is the Great White Spot.
This storm begins as spots in Saturn’s atmosphere as discrete spots and encircles the planet within six months. Often, the storm’s head touches its tail, and it sputters to death.
In the last 140 years, the Great White Spot has occurred six times, with the most recent one was seen in December 2010.
While the storm itself is well-imaged, our understanding of what triggers it is still hazy.
One explanation is that the storm, which occurs between the equator and mid-latitudes, happens during Saturn summers when the high temperatures drive winds. More than ten lightning flashes per second aren’t uncommon, either.
The Climate and Weather on Saturn
Saturn witnesses extreme weather patterns and a stormy climate.
We’ve already seen the hexagonal cloud formation in the north pole, which is caused by turbulent atmospheric movements. Wind speeds on the gas giant reach up to 500 miles per second— the second-fastest in the solar system after Neptune.
Tiny storms and hurricanes accompanied by flashes of lightning are common throughout the year. This is in part because of the difference in rotation speeds between the atmosphere and core (remember, Saturn is made up of layers of atmosphere, and each rotates with different speeds).
How Do We Know All of This?
It is true that we cannot (yet) travel to Saturn, but spacecraft can! And four of them did. Of course, Saturn does not have a surface for the spacecraft to land upon, but there was still plenty to learn from the images and data that was sent from them as they orbited the ringed planet.
The first spacecraft was Pioneer 11, which in 1979 provided the first close looks of Saturn. It also confirmed the existence of Saturn’s magnetic field and the abundance of hydrogen in the planet’s atmosphere.
In 1980 and 1981, Voyager 1 and Voyager 2 flew by Saturn. Their images revealed many interesting details and new moons in the Saturnian world, but it wasn’t until the Cassini mission in 2004 that scientists’ understanding of Saturn really cemented.
Data from the mission answered many questions about Saturn and its moon system but also raised many more. The most surprising finding from the mission came from Saturn’s moons Titan and Enceladus, which scientists believe hold many similarities to Earth.
After 13 years of studying Saturn up close, the Cassini spacecraft was plunged into the gas giant. Even then, it sent back images from Saturn’s ring system, providing the first-ever views of the rings from the inside out.
Summary
Saturn, as we saw, is nothing like the calm, serene planet that it looks in images.
Storms, hurricanes, and fast wind speeds are common on the planet throughout the year. These are driven by the different speeds at which each atmospheric layer rotates.
There are also more long-term features like the hexagonal cloud formation in the north pole. Temperature changes are not seasonal on Saturn like they are on Earth, but the gas giant does experience a variation as one moves from the core, where it is hottest, to the outer layers, where it is so cold that ammonia exists in an icy form.
Because of this variation, it is hard to give a precise answer as to the temperature of Saturn, but it ranges from -280 °F (-138 °C) at the outer surface to 21,000 °F (11,700 °C) at its core.
