Saturn’s 2010 Great White Spot storm has set a new record for largest temperature change ever recorded for a storm on Saturn. By studying the monstrous disturbance using NASA’s Cassini spacecraft, researchers spotted a massive belch of energy that sent temperatures soaring to an unprecedented 150 degrees Fahrenheit above normal in Saturn’s stratosphere, accompanied by an enormous release of ethylene gas.
Turbulent jet streams, regions where winds blow faster than in other places, churn east and west across Saturn. Scientists have been trying to understand for years the mechanism that drives these wavy structures in Saturn’s atmosphere and the source from which the jets derive their energy.
In a new study appearing in the June edition of the journal Icarus, scientists used images collected over several years by NASA’s Cassini spacecraft to discover that the heat from within the planet powers the jet streams. Condensation of water from Saturn’s internal heating led to temperature differences in the atmosphere. The temperature differences created eddies, or disturbances that move air back and forth at the same latitude, and those eddies, in turn, accelerated the jet streams like rotating gears driving a conveyor belt.
A competing theory had assumed that the energy for the temperature differences came from the sun. That is how it works in Earth’s atmosphere.
“We know the atmospheres of planets such as Saturn and Jupiter can get their energy from only two places: the sun or the internal heating. The challenge has been coming up with ways to use the data so that we can tell the difference,” said Tony Del Genio of NASA’s Goddard Institute for Space Studies, N.Y., the lead author of the paper and a member of the Cassini imaging team….
Read more: www.sciencedaily.com
These raw, unprocessed images of Saturn’s second largest moon, Rhea, were taken on March 10, 2012, by NASA’s Cassini spacecraft. This was a relatively distant flyby with a close-approach distance of 26,000 miles (42,000 kilometers), well suited for global geologic mapping.
During the flyby, Cassini captured these distinctive views of the moon’s cratered surface, creating a 30-frame mosaic of Rhea’s leading hemisphere and the side of the moon that faces away from Saturn. The observations included the large Mamaldi (300 miles, or 480 kilometers, across) and Tirawa (220 miles, or 360 kilometers, across) impact basins and the 29-kilometer (47-kilometer) ray crater Inktomi, one of the youngest surface features on Rhea (about 950 miles, or 1,530 kilometers, across).
All of Cassini’s raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/.
Read more: nasa.gov
Dione on a Diagonal
Saturn and Dione appear askew in this Cassini spacecraft view, with the north poles rotated to the right, as if they were threaded along on the thin diagonal line of the planet’s rings.
This view looks toward the anti-Saturn side of Dione (698 miles, or 1,123 kilometers across). North on Dione is up and rotated 20 degrees to the right. This view looks toward the northern, sunlit side of the rings from less than one degree above the ring plane.
The image was taken in visible green light with the Cassini spacecraft wide-angle camera on Dec. 12, 2011. The view was obtained at a distance of approximately 35,000 miles (57,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 41 degrees.
Image Credit: NASA/JPL-Caltech/Space Science Institute
The Moon and two bright companions line up across the southeast before dawn tomorrow. The closer of the Moon’s companions is Spica, the leading light of the constellation Virgo. It’s to the left or lower left of the Moon. The other is the planet Saturn, which is to the left of Spica.
Saturn is the brighter of the two, and it’s growing a little brighter night by night. By the middle of April, it’ll shine about twice as brightly as Spica.
The reason for the change in Saturn’s brightness is the changing distance between Saturn and Earth.
Right now, we’re separated by close to 950 million miles. But Earth follows a much smaller, faster orbit around the Sun, so we’re quickly catching up to Saturn. We’ll pass it in mid-April, when we’ll be about 130 million miles closer. At that range, Saturn will shine half again as bright as it is now.
Of course, the distance between Earth and Spica changes by that much, too. But the star is about 250 light-years away. At such a great range, the difference of a hundred million miles or so is insignificant. So Spica’s light holds steady all year long. And when Saturn is at its farthest from Earth, Spica outshines it.
Even as we move past Saturn, though, it’ll remain quite close to Spica in our sky. In fact, they will remain quite close until late next year, when Saturn will finally begin to pull away from its bright stellar companion. stardate.org
Le matin du 20 décembre, cherchez le croissant de Lune. Il vous permettra de trouver deux astres remarquables : l’étoile Spica et la planète Saturne. Ces deux astres sont de luminosité comparable mais ils sont en réalité très différents…
See a relevent video here
Scientists analyzing data from NASA’s Cassini spacecraft now have the first-ever, up-close details of a Saturn storm that is eight times the surface area of Earth.
On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears at approximately 35 degrees north latitude on Saturn. Pictures from Cassini’s imaging cameras show the storm wrapping around the entire planet covering approximately 1.5 billion square miles (4 billion square kilometers).
The storm is about 500 times larger than the biggest storm previously seen by Cassini during several months from 2009 to 2010. Scientists studied the sounds of the new storm’s lightning strikes and analyzed images taken between December 2010 and February 2011. Data from Cassini’s radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini’s arrival to Saturn in 2004. The data appear in a paper published this week in the journal Nature….. Continue reading Cassini Spacecraft Captures Images And Sounds Of Big Saturn Storm
PASADENA, Calif. – NASA’s Cassini spacecraft has discovered the best evidence yet for a large-scale saltwater reservoir beneath the icy crust of Saturn’s moon Enceladus. The data came from the spacecraft’s direct analysis of salt-rich ice grains close to the jets ejected from the moon.
Data from Cassini’s cosmic dust analyzer show the grains expelled from fissures, known as tiger stripes, are relatively small and predominantly low in salt far away from the moon. But closer to the moon’s surface, Cassini found that relatively large grains rich with sodium and potassium dominate the plumes. The salt-rich particles have an “ocean-like” composition and indicate that most, if not all, of the expelled ice and water vapor comes from the evaporation of liquid salt water. The findings appear in this week’s issue of the journal Nature.
“There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus’s icy surface,” said Frank Postberg, a Cassini team scientist at the University of Heidelberg, Germany, and the lead author on the paper. When water freezes, the salt is squeezed out, leaving pure water ice behind. If the plumes emanated from ice, they should have very little salt in them….. Continue reading Cassini Captures Ocean-Like Spray at Saturn Moon
Animation made using the raw images from Cassini’s flyby of Saturn’s moon, Helene on 18/6/2011