Saturn north pole hexagon in motion as seen by the now-defunct Cassini spacecraft. (Credit: NASA/JPL-Caltech/SSI/Hampton University)
A bizarre hexagonal vortex has formed above Saturn’s north pole as the planet’s northern hemisphere is the summer, the data from the international Cassini-Huygens mission revealed. The unusual vortex circulates hundreds of kilometres above the clouds in the stratosphere layer of the ringed planet’s atmosphere, a new study, published.
This warm polar vortex similar to other, previously discovered hexagon formation, also based on the Saturn of the north pole, but lower in the atmosphere. But how and whether this bizarre low – and high-elevation hexagons are related remains a mystery for scientists.
“A hexagon has spawned spontaneously and identically in two different heights, a lower in the clouds and a high in the stratosphere, or the hexagon is in fact a towering structure in a vertical range of several hundred kilometers,” Leigh Fletcher, lead author of the study and a planetary scientist at the University of Leicester in England, said in a statement. [Cassini’s Greatest Hits: Photos of Saturn and Its Moons]
NASA’s Cassini spacecraft arrived at the Saturn system in 2004, when it was summer in the planet’s southern hemisphere and winter in the northern hemisphere. At the time that the spacecraft has documented a round, warm, high-altitude vortex at Saturn’s south pole, but nothing at the north pole.
Prior to Cassini, NASA’s Voyager spacecraft had revealed a lower altitude north pole hexagon in the 1980’s. That hexagon is a long-term wave thought to be associated with Saturn’s rotation, similar to the way in which the rotation of the Earth affects the Polar jet stream.
The Cassini spacecraft took a look at this previously discovered lower height hexagon formation with multiple instruments, including the Composite Infrared Spectrometer (CIRS) — a device that measures the temperature and the composition of the objects by the capture of infrared light, according to NASA.
But because it was winter in Saturn’s northern hemisphere at that time, the temperatures in the stratosphere above the north pole were minus 252 degrees Fahrenheit (minus 158 degrees Celsius) — too cold for a reliable CIRS observations. The extreme temperatures meant Cassini had to wait for the summer, and as a result, the high-altitude regions of Saturn’s north pole went unexplored for years.
“A Saturn year covers about 30 earth years, so the winters are long,” Sandrine Guerlet, study co-author and planetary researcher at the Dynamic Meteorology Library in France, said in the statement. “Saturn only began to emerge from the depths of the northern winter in 2009 and gradually warmed up as the northern hemisphere approached summer,” Guerlet explained.
Years later, when the temperature in the northern hemisphere of Saturn is gradually increased, Cassini’s CIRS discovered the strange polar vortex, high above the north pole. “As the polar vortex became more and more visible, we have noticed that had hexagonal edges,” Guerlet said.
Cassini captured images of both a low altitude and at high altitude hexagonal vortex only at Saturn’s north pole, while the vortex discovered years earlier on Saturn’s south pole was circular. This discrepancy between the poles of Saturn led the researchers suspect that there are probably several processes at work on the planet’s two poles. The different vortexes, which suggest that the poles are asymmetrical or that the north pole vortex was still in development and the continuous development after Cassini’s demise in Sept. 2017, Fletcher said.
It is unlikely that the just described vortex is arising from a single, gigantic hexagonal column of clouds over Saturn’s north pole, because the planet of the wind change drastically with the height. And Fletcher and his colleagues have previously thought that there are waves, just like those of the previously discovered north pole hexagon, couldn’t pass up, so would remain trapped in the cloud-tops.
But Saturn presents a possible bias in the way in which waves behave.
“A way that wave “information” can leak upstairs through a process called evanescence, where the power of a wave decays with height, but is only strong enough to persist into the stratosphere,” Fletcher said.
Unravel the mystery of how Saturn’s high-altitude hexagonal vortex formed, scientists can learn more about the atmospheric effects, such as the way in which events are lower in an atmosphere of an impact on the environment in the higher areas.
“We just need to know more,” Fletcher said.
The team published its results Monday (Sept. 3) in the journal Nature Communications.
Original article on Live Science.