"Long before it's in the papers"
January 28, 2015


Saturn rings found clumpier, heavier than thought

May 23, 2005
Courtesy NASA
and World Science staff

Sat­urn’s larg­est, most compact ring con­sists of tightly packed clumps of par­t­i­cles sep­a­rat­ed by nearly emp­ty gaps, ac­cord­ing to new find­ings from NASA’s Cas­si­ni space­craft. 

This false-color im­age of Sat­urn's rings was made us­ing a Cas­si­ni in­stru­ment called the ultra­violet im­ag­ing spec­tro­graph. Sci­en­tists used it to rec­ord oc­cul­ta­tions, in which a star's bright­ness changes as the rings pass in front of it, re­veal­ing the amount of ring ma­te­ri­al be­tween the craft and the star. Cas­si­ni gave sci­en­tists the most de­tailed view yet of the B ring and found that this part of the rings is dense­ly packed with con­stant­ly col­lid­ing clumps called self-gravity wakes, sep­a­rat­ed by gaps. The clumps, 30 to 50 me­ters (100 to 160 feet) across, are too small to be seen di­rect­ly, but re­search­ers can map their dis­tri­bu­tion, shape and ori­en­ta­tion. Col­ors here in­di­cate their ori­en­ta­tion; bright­ness in­di­cates den­si­ty of ring par­t­i­cles. Those in the yel­low zone are too dense­ly packed for star­light to pass through. (Cre­dit: NA­SA/JPL/Uni­ver­s­ity of Co­lo­ra­do)

These clumps in Sat­urn’s B ring are neatly or­gan­ized and con­stantly col­lid­ing, which sur­prised sci­en­tists, they said.

“We orig­i­nally thought we would see a un­iform cloud of par­t­i­cles,” said Lar­ry Es­pos­ito, prin­ci­pal in­ves­ti­ga­tor for the Cas­si­ni ul­tra­vi­o­let im­ag­ing spec­tro­graph at the Un­ivers­ity of Col­o­rad­o, Boul­der. 

“In­stead we find that the par­t­i­cles are clumped to­geth­er with emp­ty spaces in be­tween. If you were fly­ing un­der Sat­urn’s rings in an air­plane, you would see these flashes of sun­light come through the gaps, fol­lowed by dark and so forth. This is dif­fer­ent from fly­ing un­der a un­iform cloud of par­t­i­cles.” 

Be­cause pre­vi­ous in­ter­preta­t­ions as­sumed the ring par­t­i­cles were dis­trib­ut­ed un­iformly, sci­en­tists un­der­es­ti­mated the to­tal mass of Sat­urn’s rings, re­search­ers said: the mass may ac­tu­ally be two or more times pre­vi­ous es­ti­mates. 

“These re­sults will help us un­der­stand the over­all ques­tion of the age and hence the or­i­gin of Sat­urn’s rings,” said Josh Col­well of the Un­ivers­ity of Cen­tral Flor­i­da, Or­lan­do, and a team mem­ber of the Cas­si­ni ul­tra­vi­o­let im­ag­ing spec­tro­graph. 

A pa­per de­tail­ing the re­sults ap­pears in the April 13 early on­line is­sue of the re­search jour­nal Ic­a­rus.

* * *

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Saturn’s largest and most densely packed ring is composed of tightly packed clumps of particles separated by nearly empty gaps, according to new findings from NASA’s Cassini spacecraft. These clumps in Saturn’s B ring are neatly organized and constantly colliding, which surprised scientists, they said. “The rings are different from the picture we had in our minds. We originally thought we would see a uniform cloud of particles. Instead we find that the particles are clumped together with empty spaces in between,” said Larry Esposito, principal investigator for the Cassini ultraviolet imaging spectrograph at the University of Colorado, Boulder. “If you were flying under Saturn’s rings in an airplane, you would see these flashes of sunlight come through the gaps, followed by dark and so forth. This is different from flying under a uniform cloud of particles.” Because previous interpretations assumed the ring particles were distributed uniformly, scientists underestimated the total mass of Saturn’s rings, researchers said: the mass may actually be two or more times previous estimates. “These results will help us understand the overall question of the age and hence the origin of Saturn’s rings,” said Josh Colwell of the University of Central Florida, Orlando, and a team member of the Cassini ultraviolet imaging spectrograph. A paper detailing the results appears in the April 13 early online issue of the research journal Icarus.
This false-color image of Saturn's main rings was made with data from a Cassini instrument called the ultraviolet imaging spectrograph. Scientists used the device to record occultations, in which a star's brightness changes as the rings pass in front of it. This provides a measure of the amount of ring material between the craft and the star. Cassini gave scientists the most detailed view yet of Saturn's B ring. The observations found that this part of the rings is densely packed with neatly organized, constantly colliding clumps called self-gravity wakes, separated by nearly empty gaps. The clumps, 30 to 50 meters (100 to 160 feet) across, are too small to be seen directly, but researchers can map their distribution, shape and orientation. Colors here indicate their orientation; brightness indicates density of ring particles. Those in the central yellow regions are too densely packed for starlight to pass through.