Space

July 31, 2013

NASA’s Cassini spacecraft reveals forces controlling Saturn moon jets

The intensity of jets of water ice and organic particles that shoot out from Saturn’s moon Enceladus depends on the moon’s proximity to the ringed planet, according to data obtained by NASA’s Cassini spacecraft.

The finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon. This is the first clear observation the bright plume emanating from Enceladus’ south pole varies predictably. The findings are detailed in a scientific paper in this week’s edition of Nature.

“The jets of Enceladus apparently work like adjustable garden hose nozzles,” said Matt Hedman, the paper’s lead author and a Cassini team scientist based at Cornell University in Ithaca, N.Y. “The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away. We think this has to do with how Saturn squeezes and releases the moon with its gravity.”

Cassini, which has been orbiting Saturn since 2004, discovered the jets that form the plume in 2005. The water ice and organic particles spray out from several narrow fissures nicknamed “tiger stripes.”

“The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water,” said Christophe Sotin, a co-author and Cassini team member at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present.”

For years scientists hypothesized the intensity of the jets likely varied over time, but no one had been able to show they changed in a recognizable pattern. Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini’s visual and infrared mapping spectrometer, and looking at data gathered over a long period of time.

The VIMS instrument, which analyzed a wide range of data including the hydrocarbon composition of the surface of another Saturnian moon, Titan, and the seismological signs of Saturn’s vibrations in its rings, collected more than 200 images of the Enceladus plume from 2005 to 2012.

These data show the plume was dimmest when the moon was at the closest point in its orbit to Saturn. The plume gradually brightened until Enceladus was at the most distant point, where it was three to four times brighter than the dimmest detection. This is comparable to moving from a dim hallway into a brightly lit office.

Adding the brightness data to previous models of how Saturn squeezes Enceladus, the scientists deduced the stronger gravitational squeeze near the planet reduces the opening of the tiger stripes and the amount of material spraying out. They think the relaxing of Saturn’s gravity farther away from planet allows the tiger stripes to be more open and for the spray to escape in larger quantities..

“Cassini’s time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are,” said Linda Spilker, Cassini project scientist at JPL. “We’ve come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our solar system formed.”

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 in Washington. The VIMS team is based at the University of Arizona in Tucson.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines April 24, 2015

News: More than $1 billion in U.S. emergency reconstruction aid goes missing in Afghanistan - A total of $1.3 billion that the Pentagon shipped to its force commanders in Afghanistan between 2004 and 2014 for the most critical reconstruction projects can’t be accounted for by the Defense Department, 60 percent of all such spending under an...
 
 

News Briefs April 24, 2015

German defense minister: widely used rifle has no future A widely used assault rifle has “no future” with the German military in its current form, Germany’s defense minister said April 22, escalating a dispute over the weapon’s alleged shortcomings. Ursula von der Leyen said last month that a study showed the G36 rifle has a...
 
 
Army photograph

Composites key to tougher, lighter armaments

Army photograph XM-360 test firing at Aberdeen Proving Ground, Md., in 2007, is shown. The Army is on the cusp of revolutionizing materials that go into armament construction, making for stronger, lighter and more durable weapo...
 

 

Northrop Grumman signs long-term agreement with Raytheon

Northrop Grumman has entered a long-term agreement with Raytheon to supply its LN-200 Inertial Measurement Unit for Raytheon optical targeting systems. The long-term agreement with Raytheon’s Space and Airborne Systems business extends through 2018. The LN-200 provides camera stabilization on optical targeting systems that conduct long-range surveillance and target acquisition for various...
 
 

NTTR supports first F-35B integration into USMC’s weapons school exercise

The Nevada Test and Training Range was part of history April 21, when four U.S. Marine Corps-assigned F-35B Lightning IIs participated in its first Marine Corps’ Final Exercise of the Weapons and Tactics Instructor course on the NTTR’s ranges. The Final Exercise, or FINEX, is the capstone event to the U.S. Marine Corps Marine Aviation...
 
 
AAR-Textron

AAR awarded new contract from Bell Helicopter Textron to support T64 engines

AAR announced April 22 that Bell Helicopter Textron Inc. awarded its Defense Systems & Logistics business unit a contract providing warehouse and logistics services in support of upgrading T64 engines for the Bell V-280 Val...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>