October 25, 2012
Cassini Reveals Aftermath Of Large Saturn Storm
[ Watch the Video: Saturn´s Record-Setting Storm ]
Lee Rannals for redOrbit.com - Your Universe Online
Data from Cassini's composite infrared spectrometer (CIRS) instrument revealed the storm's powerful discharge, sending the temperature in Saturn's stratosphere to 150 degrees Fahrenheit above normal.
Researchers at NASA's Goddard Space Flight Center wrote in the Astrophysical Journal that they also detected an increase in the amount of ethylene gas, which is an odorless, colorless gas not typically observed on Saturn.
"This temperature spike is so extreme it's almost unbelievable, especially in this part of Saturn's atmosphere, which typically is very stable," said Brigette Hesman, the study's lead author and a University of Maryland scientist who works at Goddard. "To get a temperature change of the same scale on Earth, you'd be going from the depths of winter in Fairbanks, Alaska, to the height of summer in the Mojave Desert."
The storm, which was detected in Saturn's northern hemisphere on December 5, 2010, grew so large that an equivalent storm on Earth would blanket most of North America from north to south, and wrap around the planet.
NASA said this type of storm occurs about every 30 Earth years on the planet, or just once every Saturn year.
The storm was the first to be observed at thermal infrared wavelengths, allowing scientists to take the temperature of Saturn's atmosphere and to track phenomena that are invisible to the naked eye.
Temperature measurements revealed two unusual beacons of warmer-than-normal air in the stratosphere. These indicate a massive release of energy into the atmosphere.
After the visible signs of the storm started to fade, CIRS data revealed the two beacons had merged. The temperature of this combined air mass shot up to more than minus 64 degrees Fahrenheit.
Hesman said the spike of ethylene generated at the same time peaked with 100 times more ethylene than scientists thought possible for Saturn. Scientists confirmed the release of the gas using the Celeste spectrometer mounted on the McMath-Pierce Solar Telescope on Kitt Peak in Arizona.
"We've really never been able to see ethylene on Saturn before, so this was a complete surprise," said Goddard's Michael Flasar, the CIRS team lead.
Cassini team associate Leigh Fletcher of Oxford University, England led a paper that describes how the stratospheric beacons were able to merge to become the largest and hottest stratospheric vortex ever detected, larger than Jupiter's Great Red Spot.
Their paper combines CIRS data with additional infrared images from other telescopes, and reports a powerful collar of clockwise winds around the vortex.
"These studies will give us new insight into some of the photochemical processes at work in the stratospheres of Saturn, other giants in our solar system, and beyond," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.