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The rings of SaturnAnother word on plasma, the “fourth stateof matter”DemoSaturn also has a liquidmetallic interior and rotatesrapidly. It also has amagnetosphere. (“dipolemoment” 560 times Earth).The University of Iowaexperiment aboard theCassini spacecraft hasmeasured waves travelingin the ionized gas of theSaturnian magnetosphere.plasma waves from the University of Iowa instrument onCassiniAre Jupiter and Saturn planets or stars?Jupiter emits 70% more radiation to space than it receivesfrom the Sun. It has an “engine” inside1

Comments on the “Pluto Controversy” of afew years ago. Whether Pluto lacked the“stuff” to be a major planetSaturn and its ringWhat you should have learned is thatJupiter and Saturn are vastly differentobjects than the terrestrial planets, andmaybe should not be in the same categoryPerhaps we should generalize a concept from antiquitybased on the huge amount that we have learned sincethe time of the Egyptians and BabyloniansRecall basic facts about Saturn Further from the Sun than Jupiter (a 9.54 au) Systematically colder as a result 95 Earth masses Diameter 9.5 times that of Earth Like Jupiter, only less extremeMost unique feature of Saturn: the ring(1) What are its properties?(2) How did it get there?2

The size and structure of Saturn’s ringThe appearance of Saturn’s ring changesduring its 29 year periodThe ring extends out to about 2.4 Saturnian radii,And is composed of 3 main rings and a prominent gapapThe ring is in Saturn’s orbital plane. Theobliquity of Saturn is 26.7 degrees.How would you determine the current tilt ofSaturn’s ring? Do we see them edge-on, orfully opened up? Use JPL solar systemsimulator, or look through a telescopeThe near-disappearance of Saturn’s ringswhen they are edge-on indicates thatthey must be very thin.Hubble Space Telescope Observation of SaturnIn 1995 when ring was edge on3

The nature of Saturn’s ringThe Cassini spacecraft at its firstapproach to Saturn, summer 2004 Maxwell (yep, the same one) proved onthe basis of physical arguments in 1859that the ring could not be a solid,orbiting disk It must be composed of billions andbillions of little moonlets, each orbitingSaturnA close-up view for a space travelerData from University of Iowa radio receiveron Cassini demonstrates that Saturn’s ringconsists of particles, many of them very smallRadio static from Saturn Ring crossingIn one of its orbits, Cassini passedthrough the outer part of the ring.Each impact of a dust particleproduced a blip of radio static4

How were the rings of Saturn formed?Why does Saturn have them?The detail in theringsThe existence of Saturn’s ring due to “tidaldisruption” Tidal “stresses” due to a difference of thegravitational force on the front and rear sideof a moon near a planet. If a moon gets closer to a planet than about2.4 planetary radii, the tidal stresses pull themoon apart In case of Saturn, a moon probably movedwithin the “tidal disruption radius” and wastorn to rubble.5

The size and structure of Saturn’s ring The ring extends out to about 2.4 Saturnian radii, And is composed of 3 main rings and a prominent gapap The appearance of Saturn’s ring changes during its 29 year period The ring is in Saturn’s orbital plane. The obliquity of Saturn is 26.7 degrees. How would you determine the current tilt of .