GEOL 3045: Planetary Geology Lysa Chizmadia Saturn’s Satellites Lysa Chizmadia Saturn’s Satellites

Introduction  At least 60 moons  Classification of Moons: –A-ring Moonlets –Ring Shepherds –Co-orbitals –Inner Large Moons  Alkyonides  Trojans –Outer Large Moons –Irregular Moons  Inuit Group  Norse Group  Gallic Group  At least 60 moons  Classification of Moons: –A-ring Moonlets –Ring Shepherds –Co-orbitals –Inner Large Moons  Alkyonides  Trojans –Outer Large Moons –Irregular Moons  Inuit Group  Norse Group  Gallic Group Image from: Image from: profile.cfmprofile.cfm?Object=Saturn&Display=Moons

A-ring Moonlets  4 discovered in 2006 by Cassini –8 more discovered in 2007  Tiny moons inside the A-ring –Diameters: 0.06 to 0.14 km  Probably formed due to shattering of inner satellite during impact  Discovered by propeller- shaped disturbances in ring  4 discovered in 2006 by Cassini –8 more discovered in 2007  Tiny moons inside the A-ring –Diameters: 0.06 to 0.14 km  Probably formed due to shattering of inner satellite during impact  Discovered by propeller- shaped disturbances in ring Image from: Photo Credit: NASA

Ring Shepherds  Orbit within or just outside rings  Sculpt the rings –Giving them sharp edges & gaps  5 named & 3 unconfirmed –Pan –Daphnis –Atlas –Prometheus –Pandora –S/2004 S3, S/2004 S4, S/2004 S6  Orbit within or just outside rings  Sculpt the rings –Giving them sharp edges & gaps  5 named & 3 unconfirmed –Pan –Daphnis –Atlas –Prometheus –Pandora –S/2004 S3, S/2004 S4, S/2004 S6 Image from: Prometheus (left) & Pandora (right) in Saturn’s F-ring Image from: Pan in Encke Division Ripples caused by Daphnis Image from: wiki/Daphnis_%28moon%29

Co-orbitals  Epimetheus & Janus  Orbit differs by only 50 km  Inner orbits are faster so must approach each other  When inner moon catches outer moon, gravitational attraction boosts inner’s momentum, increasing orbit  Opposite happens to outer moon  Thus, they trade places when they pass each other  Epimetheus & Janus  Orbit differs by only 50 km  Inner orbits are faster so must approach each other  When inner moon catches outer moon, gravitational attraction boosts inner’s momentum, increasing orbit  Opposite happens to outer moon  Thus, they trade places when they pass each other Images from: Epimetheus_%28moon%29 Image from: Janus_%28moon%29 Epimetheus Janus

Inner Large Moons  Mimas (Herschel crater)  Methone  Anthe  Pallene  Enceladus *  Tethys –Telesto (L4) –Calypso (L5)  Dione (ice cliffs) –Helene (L4) –Polydeuces (L5)  Mimas (Herschel crater)  Methone  Anthe  Pallene  Enceladus *  Tethys –Telesto (L4) –Calypso (L5)  Dione (ice cliffs) –Helene (L4) –Polydeuces (L5) Mimas Dione

Enceladus  Ice ridges & Cryovolcanism Images from:

Outer Large Moons  Rhea –Homogeneous interior –2 adjacent large craters –Possible ring system  Titan *  Hyperion –Chaotic rotation –Sponge-like texture  Iapetus –2 tone coloration –High inclination –Equitorial ridge  Rhea –Homogeneous interior –2 adjacent large craters –Possible ring system  Titan *  Hyperion –Chaotic rotation –Sponge-like texture  Iapetus –2 tone coloration –High inclination –Equitorial ridge Rhea Image from: Image from: Hyperion Images from: Iapetus

Titan  Only moon w/ dense atm –Pressure: 1.6 bars –98.4% N 2, 1.6% CH 3 & H-Cs –CH 3 must be produced  Not from comets b/c  CO  Not from nebula b/c  He, Ne  Only body with liquid on surface –Other than Earth –Liquid CH 3 lakes  Diameter: 5150 km –Mercury: 4879 km –Moon: 3474 km  Only moon w/ dense atm –Pressure: 1.6 bars –98.4% N 2, 1.6% CH 3 & H-Cs –CH 3 must be produced  Not from comets b/c  CO  Not from nebula b/c  He, Ne  Only body with liquid on surface –Other than Earth –Liquid CH 3 lakes  Diameter: 5150 km –Mercury: 4879 km –Moon: 3474 km Images from:

Irregular Moons  3 main groups –Inuit Group –Norse Group –Gallic Group  3 main groups –Inuit Group –Norse Group –Gallic Group Images from: Pheobe

Inuit Group  Prograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities:  Spectral homogeneity –Similar to Gallic Group –Break up of single object  5 members: –Kiviuq –Ijiiraq –Paaliaq –Siarnap –Tarqeq  Prograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities:  Spectral homogeneity –Similar to Gallic Group –Break up of single object  5 members: –Kiviuq –Ijiiraq –Paaliaq –Siarnap –Tarqeq Image from:

Norse Group  Retrograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities:  Composed of > 4 subgroups –two i=174  subgroups –Skathi subgroup –Narvi subgroup  Retrograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities:  Composed of > 4 subgroups –two i=174  subgroups –Skathi subgroup –Narvi subgroup Image from:

Gallic Group  Prograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities: ~0.53  Spectral homogeneity –Similar to Inuit Group –Break up of single object  4 members: –Albiorix –Bebhionn –Erriapus –Tarvos  Prograde irregular satellites  Semi-major axes: x 10 6 km  Inclinations: degrees  Eccentricities: ~0.53  Spectral homogeneity –Similar to Inuit Group –Break up of single object  4 members: –Albiorix –Bebhionn –Erriapus –Tarvos Image from:

Summary  At least 60 moons  At least 6 groups –A-ring moonlets –Shepherd moons –Co-orbitals –Inner large moons  Includes Enceladus –Outer large moons  Includes Titan –Irregular Moons  Inuit group  Norse group  Gallic group  At least 60 moons  At least 6 groups –A-ring moonlets –Shepherd moons –Co-orbitals –Inner large moons  Includes Enceladus –Outer large moons  Includes Titan –Irregular Moons  Inuit group  Norse group  Gallic group  Mimas –Herschel Crater  Dione –Whispy ice ridges  Enceladus –Ice ridges ~ Europa –Cryovolcanism  Rhea –Homogeneous interior –Possible ring system  Titan –H-C rich atmosphere –Liquid HC on surface  Hyperion –Sponge-like surface texture  Iapetus –Two-tone surface colors –Equatorial ridge  Mimas –Herschel Crater  Dione –Whispy ice ridges  Enceladus –Ice ridges ~ Europa –Cryovolcanism  Rhea –Homogeneous interior –Possible ring system  Titan –H-C rich atmosphere –Liquid HC on surface  Hyperion –Sponge-like surface texture  Iapetus –Two-tone surface colors –Equatorial ridge