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.


 
 

 
Image courtesy of NASA/CXC/M. Weiss

NASA’s Chandra X-ray Observatory finds planet that makes star act deceptively old

Image courtesy of NASA/CXC/M. Weiss A new study from NASA’s Chandra X-ray Observatory shows that a giant exoplanet, WASP-18b, is making the star that it orbits very closely act much older than it actually is. This artist&...
 
 
NASA photographs by Tom Tschida

NASA Shuttle Carrier Aircraft 911 moves to final home

NASA photographs by Tom Tschida NASA 911, one of two retired Shuttle Carrier Aircraft that ferried NASA’s space shuttles across the country for three decades, is towed from NASA Armstrong’s Bldg. 703 on its final journey to...
 
 
Image courtesy of NASA/JPL-Caltech/Univ. of Arizona

NASA’s Mars Curiosity rover arrives at Martian mountain

NASA’s Mars Curiosity rover has reached the Red Planet’s Mount Sharp, a Mount-Rainier-size mountain at the center of the vast Gale Crater and the rover mission’s long-term prime destination. “Curiosity n...
 

 

NASA announces 2014 aeronautics scholarship recipients

NASA has selected 20 students from across the nation to receive the agency’s Aeronautics Scholarship for the 2014-2015 school year. This scholarship program, which is in its seventh year, is designed to assist undergraduate and graduate students enrolled in fields of study related to aeronautics. Recipients were selected from hundreds of applications to the program....
 
 
NASA photograph by Dan Casper

NASA’s Orion spacecraft nears completion, ready for fueling

NASA photograph by Dan Casper The Orion crew module, stacked atop its service module, moved out of the Neil Armstrong Operations and Checkout Building at NASA’s Kennedy Space Center in Florida on Sept 11. Orion was transporte...
 
 

NASA awards cross-track infrared sounder instrument for the JPSS-2

NASA has awarded a sole source contract modification to Exelis, Inc., Geospatial Systems, of Fort Wayne, Ind., for the Cross-track Infrared Sounder Instrument for flight on the Joint Polar Satellite System-2 mission. This is a cost-plus-award-fee modification in the amount of $221 million. This action extends the period of performance of the contract from November...
 




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>