Saturn’s huge Northern Storm
This false-color mosaic from NASA’s Cassini spacecraft shows the tail of Saturn’s huge northern storm. In mid-September 2004, the Cassini spacecraft chronicled a similar, but smaller, storm in the southern hemisphere called the “Dragon Storm.”
The head of this storm is beyond the horizon in this view. Saturn’s atmosphere and its rings are shown here in a false color composite made from 12 images taken in near-infrared light through filters that are sensitive to varying degrees of methane absorption. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable near the top of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue because they are outside of the atmosphere and not affected by methane absorption.
The oval in the upper left of this image that appears slightly blue is the same hole in the deep clouds of the planet’s atmosphere that can be seen near the tail in a larger false-color mosaic, PIA14903. The blue color comes from the high haze overlying the hole.
This view looks toward the northern, sunlit side of the rings from just above the ring plane. The shadow of the moon Enceladus is visible on the planet in the lower left of the image.
The images were taken with the Cassini spacecraft wide-angle camera using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 890 nanometers are projected as blue. The images filtered at 728 nanometers are projected as green, and images filtered at 752 nanometers are projected as red.
The images were taken on Jan. 12, 2011, over about one hour at a distance of approximately 684,000 miles (1.1 million kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 52 degrees. The images were re-projected to the same viewing geometry, so that scale in this final mosaic is 76 miles (122 kilometers) per pixel.
Image Credit:NASA/JPL-Caltech/Space Science Institute
The storm’s 200-day active period also makes it the longest-lasting planet-encircling storm ever seen on Saturn. The previous record holder was an outburst sighted in 1903, which lingered for 150 days. The large disturbance imaged 21 years ago by NASA’s Hubble Space Telescope and comparable in size to the current storm lasted for only 55 days.
The collected images and movies from Cassini’s imaging team can be seen at http://saturn.jpl.nasa.gov/ , http://www.nasa.gov/cassini , and http://ciclops.org . They include mosaics of dozens of images stitched together and presented in true and false colors.
“The Saturn storm is more like a volcano than a terrestrial weather system,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “The pressure builds up for many years before the storm erupts. The mystery is that there’s no rock to resist the pressure – to delay the eruption for so many years.”
Cassini has taken hundreds of images of this storm as part of the imaging team’s “Saturn Storm Watch” campaign. During this effort, Cassini takes quick looks at the storm in between other scheduled observations of either Saturn or its rings and moons. The new images, together with other high-quality images collected by Cassini since 2004, allow scientists to trace back the subtle changes on the planet that preceded the storm’s formation and have revealed insights into the storm’s development, its wind speeds and the altitudes at which its changes occur.
The storm first appeared at approximately 35 degrees north latitude on Saturn and eventually wrapped itself around the entire planet to cover approximately 2 billion square miles (5 billion square kilometers). The biggest disturbance Cassini had previously witnessed on Saturn occurred in a latitude band in the southern hemisphere called “Storm Alley” because of the prevalence of thunderstorms in this region. That storm lasted several months, from 2009 into 2010. That disturbance was actually a cluster of thunderstorms, each of which lasted up to five days or so and affected only the local weather. The recent northern disturbance is a single thunderstorm that raged continuously for more than 200 days and impacted almost one-fifth of the entire northern hemisphere.
“This new storm is a completely different kind of beast compared to anything we saw on Saturn previously with Cassini,” said Kunio Sayanagi, a Cassini imaging team associate and planetary scientist at the University of California, Los Angeles. “The fact that such outbursts are episodic and keep happening on Saturn every 20 to 30 years or so is telling us something about deep inside the planet, but we have yet to figure out what it is.”
Current plans to continue the mission through 2017 will provide opportunities for Cassini to witness further changes in the planet’s atmosphere as the seasons progress to northern summer.
“It is the capability of being in orbit and able to turn a scrutinizing eye wherever it is needed that has allowed us to monitor this extraordinary phenomenon,” said Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo. “Seven years of taking advantage of such opportunities have already made Cassini one of the most scientifically productive planetary missions ever flown.”
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.
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