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August 03, 2010

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Video shows Saturn’s northern lights

Nov. 27, 2009
Courtesy Jet Propulsion Laboratory
and World Science staff

A space­craft has spot­ted the tallest known “north­ern lights” in the so­lar sys­tem, the au­ro­ras flick­er­ing in shape and bright­ness high above Sat­urn.

The find­ings come from the Cas­si­ni space­craft, a co­op­er­a­tive proj­ect of NASA, the Eu­ro­pe­an Space Agen­cy and the Ital­ian Space Agen­cy.

New vid­e­o, with col­or ar­ti­fi­cially added to orig­i­nally black and white im­ages, show changes in Sat­urn’s au­ro­ra eve­ry few min­utes, in high res­o­lu­tion. The im­ages show a pre­vi­ously un­seen ver­ti­cal pro­file to the au­ro­ras, which rip­ple in the vi­deolike tall cur­tains. These cur­tains reach more than 1,200 kilo­me­ters (750 miles) above the edge of the plan­et’s north­ern hem­i­sphere.

The vi­deoand still im­ages are on­line at three web­sites:
http://ciclops.org
http://saturn.jpl.nasa.gov
http://www.nasa.gov/cassini

Au­ro­ras oc­cur on Earth, Ju­pi­ter, Sat­urn, and a few oth­er plan­ets. Sci­en­tists say the new im­ages will help sci­en­tists bet­ter un­der­stand how they are gen­er­at­ed.

“The au­ro­ras have put on a daz­zling show, shape-shifting rap­idly and ex­pos­ing cur­tains that we sus­pected were there, but had­n’t seen on Sat­urn be­fore,” said An­drew In­ger­soll of the Cal­i­for­nia In­sti­tute of Tech­nol­o­gy in Pas­a­de­na, a mem­ber of the Cas­si­ni im­ag­ing team that pro­cessed the new vid­e­o. 

“See­ing these things on anoth­er plan­et helps us un­der­stand them a lit­tle bet­ter when we see them on Earth.” Au­ro­ras ap­pear mostly in the high lat­i­tudes near a plan­et’s mag­net­ic poles. When charged par­t­i­cles from the mag­ne­to­sphere—the mag­net­ic bub­ble sur­round­ing a plan­et—plunge in­to the plan­et’s up­per at­mos­phere, they cause the at­mos­phere to glow. The cur­tain shapes show the paths that these charged par­t­i­cles take as they flow along the lines of the mag­net­ic field be­tween the mag­ne­to­sphere and the up­permost part of the at­mos­phere.

The height of the cur­tains on Sat­urn ex­poses a key dif­fer­ence be­tween Sat­urn’s at­mos­phere and our own, In­ger­soll said. While Earth’s at­mos­phere has a lot of ox­y­gen and ni­tro­gen, Sat­urn’s at­mos­phere is com­posed pri­marily of hy­dro­gen. Be­cause hy­dro­gen is very light, the at­mos­phere and au­ro­ras reach far out from Sat­urn. Earth’s au­ro­ras tend to flare only about 100 to 500 kilo­me­ters (60 to 300 miles) above the sur­face.

The speed of the au­ro­ral changes in the vi­deo is com­pa­ra­ble to some of those on Earth, but sci­en­tists are still work­ing to un­der­stand the pro­cesses that pro­duce these rap­id changes. The height will al­so help them learn how much en­er­gy is re­quired to light up au­ro­ras.

“I was wowed when I saw these im­ages and the cur­tain,” said Ta­mas Gom­bosi of the Un­ivers­ity of Mich­i­gan in Ann Ar­bor, who chairs Cas­si­ni’s mag­ne­to­sphere and plas­ma sci­ence work­ing group. The mov­ie was as­sem­bled from nearly 500 still pic­tures span­ning 81 hours be­tween Oct. 5 and Oct. 8, 2009. Each pic­ture had an ex­po­sure time of two or three min­utes. The cam­era shot pic­tures from the night side of Sat­urn.

The im­ages were orig­i­nally ob­tained in black and white, and the im­ag­ing team high­light­ed the au­ro­ras in false-col­or or­ange. The ox­y­gen and ni­tro­gen in Earth’s up­per at­mos­phere con­trib­ute to the col­orful flashes of green, red and even pur­ple in our au­ro­ras. But sci­en­tists are still work­ing to de­ter­mine the true col­or of the au­ro­ras at Sat­urn, whose at­mos­phere lacks those chem­i­cals.

The Je­t Pro­pul­sion Lab­o­r­a­to­ry, a di­vi­sion of the Cal­i­for­nia In­sti­tute of Tech­nol­o­gy in Pas­a­de­na, Calif., man­ages the Cas­si­ni-Huygens mis­sion for NASA.

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A spacecraft has spotted the tallest known “northern lights” in the solar system, the auroras flickering in shape and brightness high above Saturn. The findings come from the Cassini spacecraft, a cooperative project of NASA, the European Space Agency and the Italian Space Agency. New video, with color artificially added to originally black and white images, show changes in Saturn’s aurora every few minutes, in high resolution. The images show a previously unseen vertical profile to the auroras, which ripple in the video like tall curtains. These curtains reach more than 1,200 kilometers (750 miles) above the edge of the planet’s northern hemisphere. The video and still images are online at three websites: http://ciclops.org http://saturn.jpl.nasa.gov http://www.nasa.gov/cassini Auroras occur on Earth, Jupiter, Saturn, and a few other planets. Scientists say the new images will help scientists better understand how they are generated. “The auroras have put on a dazzling show, shape-shifting rapidly and exposing curtains that we suspected were there, but hadn’t seen on Saturn before,” said Andrew Ingersoll of the California Institute of Technology in Pasadena, who is a member of the Cassini imaging team that processed the new video. “Seeing these things on another planet helps us understand them a little better when we see them on Earth.” Auroras appear mostly in the high latitudes near a planet’s magnetic poles. When charged particles from the magnetosphere—the magnetic bubble surrounding a planet—plunge into the planet’s upper atmosphere, they cause the atmosphere to glow. The curtain shapes show the paths that these charged particles take as they flow along the lines of the magnetic field between the magnetosphere and the uppermost part of the atmosphere. The height of the curtains on Saturn exposes a key difference between Saturn’s atmosphere and our own, Ingersoll said. While Earth’s atmosphere has a lot of oxygen and nitrogen, Saturn’s atmosphere is composed primarily of hydrogen. Because hydrogen is very light, the atmosphere and auroras reach far out from Saturn. Earth’s auroras tend to flare only about 100 to 500 kilometers (60 to 300 miles) above the surface. The speed of the auroral changes in the video is comparable to some of those on Earth, but scientists are still working to understand the processes that produce these rapid changes. The height will also help them learn how much energy is required to light up auroras. “I was wowed when I saw these images and the curtain,” said Tamas Gombosi of the University of Michigan in Ann Arbor, who chairs Cassini’s magnetosphere and plasma science working group. The movie was assembled from nearly 500 still pictures spanning 81 hours between Oct. 5 and Oct. 8, 2009. Each picture had an exposure time of two or three minutes. The camera shot pictures from the night side of Saturn. The images were originally obtained in black and white, and the imaging team highlighted the auroras in false-color orange. The oxygen and nitrogen in Earth’s upper atmosphere contribute to the colorful flashes of green, red and even purple in our auroras. But scientists are still working to determine the true color of the auroras at Saturn, whose atmosphere lacks those chemicals. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington.