Cassini Finds a Video Gamers’ Paradise at Saturn

Scientists with NASA’s Cassini mission have spotted two features shaped like the 1980s video game icon “Pac-Man” on moons of Saturn. One was observed on the moon Mimas in 2010 and the latest was observed on the moon Tethys. Image credit: NASA/JPL-Caltech/GSFC/SWRI

You could call this “Pac-Man, the Sequel.” Scientists with NASA’s Cassini mission have spotted a second feature shaped like the 1980s video game icon in the Saturn system, this time on the moon Tethys. (The first was found on Mimas in 2010). The pattern appears in thermal data obtained by Cassini’s composite infrared spectrometer, with warmer areas making up the Pac-Man shape.

“Finding a second Pac-Man in the Saturn system tells us that the processes creating these Pac-Men are more widespread than previously thought,” said Carly Howett, the lead author of a paper recently released online in the journal Icarus. “The Saturn system – and even the Jupiter system – could turn out to be a veritable arcade of these characters.”

Scientists theorize that the Pac-Man thermal shape on the Saturnian moons occurs because of the way high-energy electrons bombard low latitudes on the side of the moon that faces forward as it orbits around Saturn. The bombardment turns that part of the fluffy surface into hard-packed ice. As a result, the altered surface does not heat as rapidly in the sunshine or cool down as quickly at night as the rest of the surface, similar to how a boardwalk at the beach feels cooler during the day but warmer at night than the nearby sand. Finding another Pac-Man on Tethys confirms that high-energy electrons can dramatically alter the surface of an icy moon. Also, because the altered region on Tethys, unlike on Mimas, is also bombarded by icy particles from Enceladus’ plumes, it implies the surface alteration is occurring more quickly than its recoating by plume particles.

“Studies at infrared wavelengths give us a tremendous amount of information about the processes that shape planets and moons,” said Mike Flasar, the spectrometer’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Md. “A result like this underscores just how powerful these observations are.”

Scientists saw the new Pac-Man on Tethys in data obtained on Sept. 14, 2011, where daytime temperatures inside the mouth of Pac-Man were seen to be cooler than their surroundings by 29 degrees Fahrenheit (15 kelvins). The warmest temperature recorded was a chilly minus 300 degrees Fahrenheit (90 kelvins), which is actually slightly cooler than the warmest temperature at Mimas (about minus 290 degrees Fahrenheit, or 95 kelvins). At Tethys, unlike Mimas, the Pac-Man pattern can also be seen subtly in visible-light images of the surface, as a dark lens-shaped region. This brightness variation was first noticed by NASA’s Voyager spacecraft in 1980.

“Finding a new Pac-Man demonstrates the diversity of processes at work in the Saturn system,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Future Cassini observations may reveal other new phenomena that will surprise us and help us better understand the evolution of moons in the Saturn system and beyond.”

Read more: www.jpl.nasa.gov

Video: Saturn’s Record-Setting Storm

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.


http://youtu.be/O7O8Hsuxjyo

Read more: nasa.gov  – badastronomy

Cassini Shows Why Jet Streams Cross-Cut Saturn

A particularly strong jet stream churns through Saturn’s northern hemisphere in this false-color view from NASA’s Cassini spacecraft. (Credit: NASA/JPL-Caltech/SSI)

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

Cassini Captures New Images of Icy Moon

NASA's Cassini spacecraft took this raw, unprocessed image of Saturn's moon Rhea on March 10, 2012. The camera was pointing toward Rhea at approximately 26,019 miles (41,873 kilometers) away.

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.

March 10, 2012. The camera was pointing toward Rhea at approximately 26,157 miles (42,096 kilometers) away. Credit: NASA/JPL-Caltech/SSI

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).

Rhea's Surface NASA's Cassini spacecraft took this raw, unprocessed image of Saturn's moon Rhea on March 10, 2012. The camera was pointing toward Rhea at approximately 26,257 miles (42,258 kilometers) away.

All of Cassini’s raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/.

Read more: nasa.gov

Saturn and Its Moon Dione

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

Moon, Saturn and Spica

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

Cassini Spacecraft Captures Images And Sounds Of Big Saturn Storm

The huge storm churning through the atmosphere in Saturn's northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft

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