October 27th, 2012 by James Ayre
An enormous storm was recently observed on Saturn by NASA’s Cassini spacecraft. Such storms have rarely been seen on Saturn, and this recent one was the largest one yet.
The data taken by Cassini revealed enormous record-setting ‘disturbances’ in the upper atmosphere of the planet, even long after any sign of the storm had dissipated.
“Data from Cassini’s composite infrared spectrometer (CIRS) instrument revealed the storm’s powerful discharge sent the temperature in Saturn’s stratosphere soaring 150 degrees Fahrenheit (83 kelvins) above normal,” NASA notes. “At the same time, researchers at NASA’s Goddard Space Flight Center
in Greenbelt, Md., detected a huge increase in the amount of ethylene gas, the origin of which is a mystery.”
Ethylene is a strange find on Saturn; the colorless, odorless gas has rarely been seen on Saturn. The gas is associated primarily with biological processes on the Earth.
“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 was first observed by NASA’s Cassini in the northern hemisphere of Saturn on Dec. 5, 2010. The storm grew to such an enormous size that if a storm of the same size occurred on the Earth it “would blanket most of North America from north to south and wrap around our planet many times.” Giant storms like this are thought to occur on Saturn roughly every 30 or so Earth years, which equals about one Saturn year.
NASA adds: “Not only was this the first storm of its kind to be studied by a spacecraft in orbit around the planet, but it was the first to be observed at thermal infrared wavelengths. Infrared data from CIRS allowed scientists to take the temperature of Saturn’s atmosphere and to track phenomena that are invisible to the naked eye.
“Temperature measurements by CIRS, first published in May 2011, revealed two unusual beacons of warmer-than-normal air shining brightly in the stratosphere. These indicated 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 (above 220 kelvins).”
The researchers say that that the huge spike of ethylene that was generated peaked at a level 100 times higher than had been thought possible on Saturn. The release of ethylene was confirmed by researchers from Goddard, using the Celeste spectrometer mounted on the McMath-Pierce Solar Telescope on Kitt Peak in Arizona.
The researchers are still trying to determine the origin of the ethylene, but have said that a large reservoir deep in the atmosphere was very unlikely.
“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.
“A complementary paper led by Cassini team associate Leigh Fletcher of Oxford University, England, describes how the two stratospheric beacons merged to become the largest and hottest stratospheric vortex ever detected in our solar system. Initially, it was larger than Jupiter’s Great Red Spot,” NASA notes.
This paper, published in the journal Icarus combines data taken by CIRS with infrared images from a variety of other Earth-based telescopes. And was the origin of the observation that there was also a “powerful collar of clockwise winds — encompassing a bizarre soup of gases — 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, Calif.
The new findings were just published on November 20th in the Astrophysical Journal.
Some background on Cassini:
“Cassini–Huygens is a flagship-class NASA-ESA-ASI robotic spacecraft sent to the Saturn system. It has studied the planet and its many natural satellites since arriving there in 2004, also observing Jupiter, the Heliosphere, and testing the theory of relativity. Launched in 1997 after nearly two decades of gestation, it includes a Saturn orbiter and an atmospheric probe/lander for the moon Titan called Huygens, which entered and landed on Titan in 2005. Cassini is the fourth space probe to visit Saturn and the first to enter orbit, and its mission is ongoing as of 2012.”
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