April 30th, 2013 by James Ayre
A beautiful image of an enormous hurricane churning at Saturn’s north pole has been captured by NASA’s Cassini spacecraft. This image is the first close-up, visible-light view of this behemoth storm, as it was previously obscured by the darkness of Saturn’s north polar winter when Cassini arrived in 2003.
In addition to being beautiful, the high-resolution photos have provided some specifics on the storm. The hurricane’s eye is roughly 1,250 miles wide, which means that it’s 20 times bigger than the typical hurricane eye on the Earth. “Thin, bright clouds at the outer edge of the hurricane are traveling 330 mph. The hurricane swirls inside a large, mysterious, six-sided weather pattern known as the hexagon.”
“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” stated Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”
Researchers are very interested in the Saturn hurricane as they think that it may lead to some new insight into how the hurricanes on the Earth function. Even though there isn’t any known body of water anywhere near these clouds high up in Saturn’s atmosphere, “learning how these Saturnian storms use water vapor could tell scientists more about how terrestrial hurricanes are generated and sustained.”
The hurricanes that we are used to seeing on the Earth, and also Saturn’s north polar vortex, both possess a central eye where there are no clouds or only very low clouds. Other features that are common to the both include: “high clouds forming an eye wall, other high clouds spiraling around the eye, and a counter-clockwise spin in the northern hemisphere.”
But there are some major differences between the two; the primary of which is that on Saturn the storms are of course much larger and spin ‘surprisingly’ fast. On Saturn, “the wind in the eye wall blows more than four times faster than hurricane-force winds on Earth. Unlike terrestrial hurricanes, which tend to move, the Saturnian hurricane is locked onto the planet’s north pole. On Earth, hurricanes tend to drift northward because of the forces acting on the fast swirls of wind as the planet rotates. The one on Saturn does not drift and is already as far north as it can be.”
“The polar hurricane has nowhere else to go, and that’s likely why it’s stuck at the pole,” stated Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Hampton, Va.
Researchers are currently of the opinion that the enormous storm has probably been going for years. “When Cassini arrived in the Saturn system in 2004, Saturn’s north pole was dark because the planet was in the middle of its north polar winter. During that time, the Cassini spacecraft’s composite infrared spectrometer and visual and infrared mapping spectrometer detected a great vortex, but a visible-light view had to wait for the passing of the equinox in August 2009. Only then did sunlight begin flooding Saturn’s northern hemisphere. The view required a change in the angle of Cassini’s orbits around Saturn so the spacecraft could see the poles.”
“Such a stunning and mesmerizing view of the hurricane-like storm at the north pole is only possible because Cassini is on a sportier course, with orbits tilted to loop the spacecraft above and below Saturn’s equatorial plane,” stated Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “You cannot see the polar regions very well from an equatorial orbit. Observing the planet from different vantage points reveals more about the cloud layers that cover the entirety of the planet.”
“Cassini changes its orbital inclination for such an observing campaign only once every few years. Because the spacecraft uses flybys of Saturn’s moon Titan to change the angle of its orbit, the inclined trajectories require attentive oversight from navigators. The path requires careful planning years in advance and sticking very precisely to the planned itinerary to ensure enough propellant is available for the spacecraft to reach future planned orbits and encounters.”
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is run by JPL, for NASA’s Science Mission Directorate in Washington. The Cassini orbiter, along with both of its onboard cameras, were designed, developed and assembled at JPL.
The Cassini mission has produced some incredible photos of the Saturn system. Including image of the surfaces of the moon Titan, amongst other amazing images. Below I’ve posted some of my favorites:
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