This set of images from NASA's Cassini
mission shows the evolution of a massive thunder-and-lightning storm
that circled all the way around Saturn and fizzled when it ran into its
own tail. The storm was first detected on Dec. 5, 2010. Image credit:
NASA/JPL-Caltech/SSI/Hampton University.
› Full image and caption
This mosaic of false-color images from
NASA's Cassini spacecraft shows what a giant storm in Saturn's northern
hemisphere looked like about a month after it began. Image credit:
NASA/JPL-Caltech/SSI/Hampton University. › Full image and caption
A vortex that was part of a giant storm
on Saturn slowly dissipates over time in this set of false color images
from NASA's Cassini spacecraft. Image credit:
NASA/JPL-Caltech/SSI/Hampton University. › Full image and caption
This image from NASA's Cassini
spacecraft reveals the wind patterns within a large vortex that was
spawned by a giant northern storm on Saturn. Image credit:
NASA/JPL-Caltech/SSI/Hampton University.
› Full image and caption
This three-frame animation from NASA's
Cassini spacecraft shows the swirling clouds in a vortex spawned by a
great northern storm on Saturn. Image credit:
NASA/JPL-Caltech/SSI/Hampton University. › See animation
Call it a Saturnian version of the Ouroboros, the mythical serpent that
bites its own tail. In a new paper that provides the most detail yet
about the life and death of a monstrous thunder-and-lightning storm on
Saturn, scientists from NASA's Cassini mission describe how the massive
storm churned around the planet until it encountered its own tail and
sputtered out. It is the first time scientists have observed a storm
consume itself in this way anywhere in the solar system.
"This Saturn storm behaved like a terrestrial hurricane - but with a
twist unique to Saturn," said Andrew Ingersoll, a Cassini imaging team
member based at the California Institute of Technology, Pasadena, who is
a co-author on the new paper in the journal Icarus. "Even the giant
storms at Jupiter don't consume themselves like this, which goes to show
that nature can play many awe-inspiring variations on a theme and
surprise us again and again."
Earth's hurricanes feed off the energy of warm water and leave a
cold-water wake. This storm in Saturn's northern hemisphere also feasted
off warm "air" in the gas giant's atmosphere. The storm, first detected
on Dec. 5, 2010, and tracked by Cassini's radio and plasma wave
subsystem and imaging cameras, erupted around 33 degrees north latitude.
Shortly after the bright, turbulent head of the storm emerged and
started moving west, it spawned a clockwise-spinning vortex that drifted
much more slowly. Within months, the storm wrapped around the planet at
that latitude, stretching about 190,000 miles (300,000 kilometers) in
circumference, thundering and throwing lightning along the way.
Terrestrial storms have never run into their own wakes - they encounter
topographic features like mountains first and expend themselves. But
Saturn has no land to stop its hurricanes. The bright, turbulent storm
head was able to chomp all the way around the planet. It was only when
the head of the storm ran into the vortex in June 2011 that the massive,
convective storm faded away. Why the encounter would shut down the
storm is still a mystery.
By Aug. 28, after 267 days, the Saturn storm stopped thundering for
good. While Cassini's infrared detectors continue to track some
lingering effects in higher layers of Saturn's atmosphere, the
troposphere -- which is the weather-producing layer, lower in the
atmosphere - has been quiet at that latitude.
"This thunder-and-lightning storm on Saturn was a beast," said Kunio
Sayanagi, the paper's lead author and a Cassini imaging team associate
at Hampton University in Virginia. "The storm maintained its intensity
for an unusually long time. The storm head itself thrashed for 201 days,
and its updraft erupted with an intensity that would have sucked out
the entire volume of Earth's atmosphere in 150 days. And it also created
the largest vortex ever observed in the troposphere of Saturn,
expanding up to 7,500 miles [12,000 kilometers] across."
The vortex grew to be as large as the giant storm known as Oval BA on
Jupiter. But Oval BA and Jupiter's more famous storm - the Great Red
Spot - are not thunder-and-lightning storms. Jupiter's storms also have a
quiet center, unlike the violence at the center of Saturn's storms.
"Cassini's stay in the Saturn system has enabled us to marvel at the
power of this storm," said Scott Edgington, Cassini's deputy project
scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We
had front-row seats to a wonderful adventure movie and got to watch the
whole plot from start to finish. These kinds of data help scientists
compare weather patterns around our solar system and learn what sustains
and extinguishes them."
This storm was the longest running of the massive storms that appear to
break out in Saturn's northern hemisphere once every Saturn year (30
Earth years). The longest storm of any size ever detected on Saturn
actually unfolded over 334 days in 2009 in an area known as "Storm
Alley" in the southern hemisphere, but it was about 100 times smaller in
area than the latest northern storm.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. JPL manages the
mission for NASA's Science Mission Directorate, Washington. The Cassini
orbiter and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team consists of scientists from the U.S.,
England, France and Germany. The imaging operations center is based at
the Space Science Institute in Boulder, Colo.
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov
