According to a news release from the University of Wisconsin-Madison, a monster storm is detected across the northern hemisphere of Saturn once every 30 years or so. In 2010, the sixth massive storm on Saturn spotted by humans started churning. It rapidly expanded to superstorm size, stretching 15,000 kilometers in width and observable to amateur space enthusiasts on Earth as a giant white spot moving across the surface of the ringed planet.

Using near-infrared spectral measurements obtained by NASA’s Cassini orbiter and investigation of near-infrared color signatures by researchers at the University of Wisconsin-Madison, scientists are closer than ever before to creating a picture of the structure of Saturn’s atmosphere at depths usually hidden by a thick high-altitude haze.

Researchers recently discovered that cloud particles at the top of the massive storm are made up of a combination of three substances: water ice, ammonia ice, and an unresolved third substance that may be ammonium hydrosulfide. They note that the observations are in keeping with clouds of varied chemical compositions existing side-by-side, although a more likely scenario is that the individual cloud particles are made up of two or all three of the materials.

This is the first time that water ice has been observed on Saturn.

“We think this huge thunderstorm is driving these cloud particles upward, sort of like a volcano bringing up material from the depths and making it visible from outside the atmosphere,” says Lawrence Sromovsky, a senior scientist at UW-Madison. “The upper haze is so optically pretty thick that it is only in the stormy regions where the haze is penetrated by powerful updrafts that you can see evidence for the ammonia ice and the water ice. Those storm particles have an infrared color signature that is very different from the haze particles in the surrounding atmosphere.”

Scientists think that the ringed planet’s atmosphere is layered: a deck of water clouds is at the bottom, with ammonia hydrosulfide clouds in the middle, and ammonia clouds near the top, just below an upper tropospheric haze of undetermined composition that hides nearly everything.

Cassini and the monster storm offered scientists an opportunity to look beneath the haze and acquire more information about the dynamics and chemical composition of the ringed planet’s deep atmosphere.

According to researchers, the monster storm functions a lot like the smaller convective events on Earth, where air and water vapor are forced high into the atmosphere, creating thunderstorm clouds. However, the storms on Saturn are much more violent, with models suggesting vertical winds of more than 300 miles per hour.

“It starts at the water cloud level and develops a huge convective tower. It is similar to a big thunderstorm, only 10 to 20 times taller and covering an even greater area,” Sromovsky says.

The research offers support for models of the ringed planet’s monster storms as well as earlier observations that found water and ammonia in vapor form. The detection of water ice, according to Sromovsky, supports the hypothesis that Saturn’s giant storms are powered by condensation of water and come from deep in the atmosphere, approximately 200 kilometers below the visible cloud deck.

“The water could only have risen from below, driven upward by powerful convection originating deep in the atmosphere. The water vapor condenses and freezes as it rises. It then likely becomes coated with more volatile materials like ammonium hydrosulfide and ammonia as the temperature decreases with their ascent,” Sromovsky notes.

The study’s findings are described in greater detail in the journal Icarus.