Researchers have created a 3D model that simulates Saturn's atmosphere, shedding light on one of its most curious features - a hexagonal storm that persists on its north pole.
The model was developed by Rakesh Yadav and Jeremy Bloxham, both from the Department of Earth and Planetary Science from Harvard University. Details of their work are published in the Proceedings of the National Academy of Sciences.
Saturn's Hexagon
Aside from its icy and rocky rings, Saturn has been a subject of curiosity among astrophysicists thanks to its six-sided atmospheric phenomenon. First discovered by the Voyager mission in 1981 and later visited by the Cassini - Huygens mission - the joint mission between the United States' NASA and Europe's ESA.
This persisting hexagonal cloud pattern covers a diameter of approximately 29,000 kilometers (18,000 miles), with each side of the hexagon about 14,500 kilometers (9,000 miles). Thermal images from past missions show that it goes about 60 miles deep into the ringed planet's atmosphere.
Scientists from Oxford University developed an earlier attempt to explain the formation of this uncommon weather system. Creating a laboratory model based on spacecraft data and prior Earth-based studies, researchers presented an "alternative explanation" that follows the instability of geostrophic barotropic jets. Also, by analyzing the Saturn atmosphere's wind profile, they were able to establish that the wind systems in their model support the existence of this hexagonal storm.
Simulating Saturn's Atmosphere with a 3D Model
By creating a 3D simulation of the planet's atmosphere, Yadev and Bloxham believe that they are gaining clues about how this weather system is formed.
"We see storms on Earth regularly, and they are always spiraling, sometimes circular, but never something with hexagon segments or polygons with edges," explained Yadav, describing it as "striking and completely unexpected." The question surrounding the giant hexagon is how does something this large form and stay for a long time on a planet such as Saturn.
In their report, researchers propose that the unnatural six-sided phenomenon happens when Saturn's atmospheric flows, deep in its atmosphere, create various small and large vortices and cyclones. These formations surround a larger horizontal jet stream that blows eastward near the planet's north pole, with this stream having many storms within it.
As the cyclones from Saturn's atmospheric flows interact with those from the horizontal jet stream, these interacting systems are mostly confined to its current location, with a "pinching process" warping the jetstream at six spots, creating the now-famous Saturn's hexagon.
"This jet is going around and around the planet, and it has to coexist with these localized [smaller] storms," Yadav said. Their paper also reported that this hexagonal flow is a "striking example of turbulent self-organization." Their model followed Saturn's zonal jets, polar cyclone, and six-sided figures like Saturn's hexagon.
While the researcher's simulation model was not able to recreate a hexagon like the one on Saturn - creating a nonagon (nine-sided polygon) that moved faster than the actual storm - it does present a proof of concept on how similar systems were formed and were able to persist since it was first observed.
