If you ask people for the name of a planet which has massive storms, the first which pops into most peoples’ minds is Jupiter, with its great red spot. But Jupiter is certainly not the only gas giant with inclement weather. Our solar system’s second largest planet, Saturn, also shows some vast storms amidst its clouds, and they’re no less dramatic than Jupiter’s.
Once every Saturnian year (roughly 28 Earth years), Saturn is ravaged by storms so huge that they can be easily seen from Earth, over 1.2 billion km (745 million miles) away. Known as great white spots, these storms seem to coincide with Saturn’s summer solstice, but being so infrequent, only a handful have ever been observed.
As a great white spot ravages its way through Saturn’s upper cloud decks, it leaves a trail of carnage in its wake — encircling the entire planet, and causing immense lightning strikes.
Even though the Cassini probe has been in orbit around Saturn for years now, sending us both fascinating data and beautiful images, Saturn’s periodic storms are still quite poorly understood. And when things are poorly understood, that’s when the theoreticians can get to work.
A group of researchers from the Planetary Sciences Group, at the University of the Basque Country, took a closer look at this puzzle. Led by Enrique García Melendo from the Fundació Observatori Esteve Duran in Catalonia, they used Cassini data to construct a mathematical model of Saturn’s storms.
Saturn’s white spots disrupt the planet’s atmosphere globally, and typically consist of a “head” that leaves a trail behind it in the planet’s atmosphere. To get a better idea of what processes may be happening in Saturn’s atmosphere, researchers took a closer look at the head of a great white spot — and at the focus of the storm.
The focus is the storm’s source; the point where it all started, buried deep within the planet’s atmosphere. In fact, the focus of a great white spot originates around 300 km (186 miles) below Saturn’s familiar yellow cloud decks. This causes a huge upwelling of material from much deeper inside Saturn’s atmosphere.
Cassini imaging used in the study also shows that the head winds in these storms reach speeds of around 500 km/h (310 mph), and that the highest of those winds are found around 40 km (25 miles) higher than regular clouds. In the head region of these storms, the raging storm interacts with the rest of the planet’s atmosphere, creating intense sustained winds.
Saturn’s white spots have been observed before to show an increase in a gas called phosphine, and a decrease in acetylene, as compared with the natural state of Saturn’s clouds. The latest study seems to confirm that one chemical which is churned to the surface in a great white spot is water — meaning that these white clouds on Saturn are made of similar stuff to the white clouds here on Earth.
It’s this upwelling of water vapor being transported up to the highest levels of the planet’s atmosphere that releases such huge amounts of energy. This interacts with Saturn’s ferocious prevailing winds, which can reach peak speeds of up to 1800 km/h (1118 mph) — the second strongest in the solar system. The interaction between these savage winds serve to power Saturn’s stormy summer season.
“We did not expect to find such violent circulation in the region of the development of the storm, which is a symptom of the particularly violent interaction between the storm and the planet’s atmosphere,” explained García, whose model managed to accurately recreate the storm in a computer simulation.
Gas giants are fascinating worlds, and even though they dominate the planets in our solar system, we still have so much more to understand about their weather systems. This latest work on Saturn’s atmosphere may help us to better understand the red spots on Jupiter, the dark spots on Neptune, and even the weather systems here on Earth.
The paper for this research is available in the journal Nature Geoscience.
Image: The 2010 storm on Saturn, and the trail it left behind it in Saturn’s atmosphere. Credit: NASA/JPL-Caltech/Space Science Institute