NASA has released this week the best views yet of a bizarre hexagon-shaped cloud that blankets Saturn’s north polar region, courtesy of the Cassini spacecraft.
First seen by the Voyager probe during its flyby in the early 1980s, this six-sided weather system stretches 15,000 miles (25,000 kilometers) across and contains storms of various sizes, including a distinct vortex that appears to sit directly over the planet’s north pole.
“A hurricane on Earth typically lasts a week, but this has been here for decades—and who knows—maybe centuries,” said Andrew Ingersoll, Cassini team scientist
Packing winds clocked at 200 miles (322 kilometers) per hour, planetary scientists believe the hexagon—unique amongst all the planets in the solar system—is a wavy jet stream.
“The hexagon is just a current of air,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena in a press statement, “and weather features out there that share similarities to this are notoriously turbulent and unstable.”
Unlike Earth, where landforms disrupt weather patterns, Saturn is a gas giant. That means jet streams like the hexagon can whirl around the planet unimpeded for long periods of time.
But the hexagon’s staying power is a boon for researchers. The oddly-shaped jet stream’s persistence allowed the Cassini spacecraft to take advantage of favorable light angles—as the gas giant’s northern hemisphere tilted more toward the sun in 2012, light was able to illuminate more areas of Saturn’s north pole.
This enabled cameras onboard Cassini to capture multiple frames over a ten-hour period, allowing scientists to stitch together a movie (click on first picture to see) clearly showing the motion of cloud structures within the hexagon.
The largest of the hurricane-like vortices rotating in the opposite direction of the hexagon spans about 2,200 miles (3,500 kilometers) across, or about twice the size of the largest hurricane recorded on Earth, says NASA.
While these images are jaw-dropping, the best may be yet to come, say NASA scientists.
“As we approach Saturn’s summer solstice in 2017, lighting conditions over its north pole will improve, and we are excited to track the changes that occur both inside and outside the hexagon boundary,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.