Wavelike Structure in Saturn’s RingsOverviewHistorySlide 4Saturn’s Ring SystemSlide 6SatellitesWavelike StructureVoyager Occultation ExperimentsSlide 10Spiral Density WavesSlide 12Slide 13Feature SearchPossible Density WavePrometheus 5:4 Surface Mass Density ResultsMimas 4:1The GapWakesPanPossible Wakes near 119950 kmPossible Wake?Wake FitsIrregular StructureSources of Irregular StructureInner B Ring – Large StructureInner B Ring Finer Irregular StructureC Ring 1000 km wavesRinglets in the C RingSlide 30ObservationsAcknowledgementsWavelike Structure in Wavelike Structure in Saturn’s RingsSaturn’s RingsBenjamin PollardBenjamin Pollard2/09/062/09/06OverviewOverviewRing SystemRing SystemHistory History DescriptionDescriptionSatellitesSatellitesTypes of StructureTypes of StructureVoyager Occultation ExperimentsVoyager Occultation ExperimentsData and Analysis MethodData and Analysis MethodObserved Ring StructureObserved Ring StructureDensity wavesDensity wavesWakesWakesIrregular StructureIrregular StructureHistoryHistory• Galileo – 1610• Christian Huygens - 1655• Jean Chapelain – 1660• Jean-Dominique Cassini – 1660’s• James Clerk Maxwell - 1857Ring Particle ModelsSaturn’s Ring SystemSaturn’s Ring SystemApproximately 340,000 km from edge to edgeApproximately 340,000 km from edge to edge100 meters thick100 meters thick7 major rings7 major ringsLess than 10 million years old?Less than 10 million years old?Saturn’s Ring System Saturn’s Ring System CCAABBEncke GapCassini DivisionCassini ISSSatellitesSatellites39 known satellites39 known satellitesDiameter of 7 km to 5150 Diameter of 7 km to 5150 kmkmResponsible for some Responsible for some ring structurering structureProduce waves in the Produce waves in the ringsringsSpiral density wavesSpiral density wavesBending wavesBending wavesWakesWakesShepherd F ringShepherd F ringGaps and RingletsGaps and RingletsWavelike StructureWavelike StructureDensity WavesDensity WavesBending WavesBending WavesWakesWakesIrregular StructureIrregular StructureCassini UVISCassini ISSCassini ISSVoyager Occultation ExperimentsVoyager Occultation ExperimentsVoyager 1Voyager 1November 13, 1980November 13, 1980Radio Science Experiment (RSS)Radio Science Experiment (RSS)Spacecraft occulted from earthSpacecraft occulted from earthMaximum resolution of 0.2 km Maximum resolution of 0.2 km (RSS)(RSS)Voyager 2 Voyager 2 August 25, 1981August 25, 1981Photopolarimeter Experiment Photopolarimeter Experiment (PPS)(PPS)Ultraviolet Spectrometer Ultraviolet Spectrometer Experiment (UVS)Experiment (UVS)The star The star δδ Scorpii occulted Scorpii occultedMaximum resolution of 0.1 km Maximum resolution of 0.1 km (PPS) and 3.5 km (UVS)(PPS) and 3.5 km (UVS)MethodsMethods20 kmSpiral Density WavesSpiral Density WavesPPSDensity Waves in the A ringPPSRSS XRSS S0Log S (σ cm4/s2)001122000000000000000011112222Optical DepthOptical DepthOptical DepthF (cy/km)F (cy/km)F (cy/km)111Calculated Surface Mass Densities From Spiral Density WavesRANGE (km)Surface Mass Density (g/cm2)246810120Feature SearchFeature SearchSearched C ring and Searched C ring and Cassini Division for Cassini Division for possible wave possible wave formations formations Two promising Two promising features appeared in features appeared in the Cassini Divisionthe Cassini DivisionOptical DepthFrequency (cycles/km)Frequency (cycles/km)Possible Density Wave Possible Density Wave Prometheus 5:4 Prometheus 5:4 located in the Cassini located in the Cassini Division at 120,302 km Division at 120,302 km Surface mass density Surface mass density measured in all three measured in all three data setsdata setsSurface mass density Surface mass density of ~30 g/cmof ~30 g/cm22Very high value for Very high value for Cassini DivisionCassini DivisionRange (km)1.1..-.Frequency (cycles/km)Prometheus 5:4 Surface Mass Prometheus 5:4 Surface Mass Density ResultsDensity ResultsRSS X BandFrequency (cycles/km).....12Mimas 4:1Mimas 4:1Located in the C ring Located in the C ring at 74892 kmat 74892 km16 km long wavetrain16 km long wavetrainPreviously calculated Previously calculated surface mass density surface mass density 1.0 +- 0.1 g/cm1.0 +- 0.1 g/cm22 and and 1.1 +- 0.1 g/cm1.1 +- 0.1 g/cm22Our calculated Our calculated surface mass density surface mass density ~5 g/cm~5 g/cm227.....Optical DepthThe GapThe Gap1.1..-.Frequency (cycles/km)Range (km)WakesWakesCaused by moonlets Caused by moonlets embedded in ringsembedded in ringsSimilar to boat traveling Similar to boat traveling through waterthrough waterWake features can be Wake features can be modeled based upon modeled based upon position of moonposition of moonPanPanLocated in the Encke Gap Located in the Encke Gap in Saturn’s A ringin Saturn’s A ringApproximately 10 km in Approximately 10 km in diameterdiameterDiscovered in 1990 using Discovered in 1990 using Voyager occultation dataVoyager occultation dataPossible Wakes near 119950 kmPossible Wakes near 119950 kmSatellite located somewhere near 119950 kmSatellite located somewhere near 119950 kmGap is about half the size of Encke GapGap is about half the size of Encke GapPossible wakes visible in both RSS and PPS dataPossible wakes visible in both RSS and PPS dataOptical Depth1..2..- .11Possible Wake?Possible Wake?Wake Fits Wake Fits RSS inner fit θ = 295º RSS outer fit θ = 65ºPPS inner fit θ = 247º PPS outer fit θ = 113ºIrregular StructureIrregular StructureSources of Irregular Structure Sources of Irregular Structure Ballistic Transport from meteoritic collisionsBallistic Transport from meteoritic collisions100 km wavelengths100 km wavelengthsC Ring and Inner B RingC Ring and Inner B RingDurisen, R.H. An Instability in Planetary Rings Due to Ballistic Transport. Durisen, R.H. An Instability in Planetary Rings Due to Ballistic Transport. IcarusIcarus 115, 66-85 115, 66-85 (1995).(1995).Ring Particle AssembliesRing Particle AssembliesUp to 50 - 100 km wavelengthsUp to 50 - 100 km wavelengthsB RingB RingTremaine, S. On the Origin of Irregular Structure in Saturn’s Rings. Tremaine, S. On the Origin of Irregular Structure in Saturn’s Rings. The Astronomical JournalThe Astronomical Journal 125, 894 – 901 (2003).125, 894 – 901 (2003).Inner B Ring – Large StructureInner