GEOL 3045: Planetary Geology

Lysa ChizmadiaSaturn’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

Image from: http://en.wikipedia.org/wiki/Saturn

Image from: http://solarsystem.nasa.gov/planets/profile.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

Image from: http://www.theregister.co.uk/2007/10/25/moonlets_a_ring/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

S6Image from: http://en.wikipedia.org/wiki/Shepherd_satellite

Prometheus (left) & Pandora (right) in Saturn’s F-ring

Image from:http://en.wikipedia.org/wiki/Pan_%28moon%29

Pan in Encke Division

Ripples caused by Daphnis

Image from: http://en.wikipedia.org/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

Images from: http://en.wikipedia.org/wiki/Epimetheus_%28moon%29

Image from: http://en.wikipedia.org/wiki/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)

http://en.wikipedia.org/wiki/Dione_%28moon%29

Mimas

Dione

http://en.wikipedia.org/wiki/Mimas_%28moon%29

Enceladus Ice ridges &

Cryovolcanism

Images from: http://en.wikipedia.org/wiki/Enceladus_%28moon%29

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

Image from: http://en.wikipedia.org/wiki/Rhea_%28moon%29Image from: http://en.wikipedia.org/wiki/Hyperion_%28moon%29

Hyperion

Images from: http://en.wikipedia.org/wiki/Iapetus_%28moon%29

Iapetus Iapetus

Titan Only moon w/ dense atm

– Pressure: 1.6 bars– 98.4% N2, 1.6% CH3 & H-Cs – CH3 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 CH3 lakes

Diameter: 5150 km– Mercury: 4879 km– Moon: 3474 km

Images from: http://en.wikipedia.org/wiki/Titan_%28moon%29

Irregular Moons 3 main groups

– Inuit Group– Norse Group– Gallic Group

Images from: http://en.wikipedia.org/wiki/Phoebe_%28moon%29

Pheobe

Inuit Group Prograde irregular satellites Semi-major axes: 11-18 x 106 km Inclinations: 40-50 degrees Eccentricities: 0.15-0.48 Spectral homogeneity

– Similar to Gallic Group– Break up of single object

5 members:– Kiviuq– Ijiiraq– Paaliaq– Siarnap– Tarqeq

Image from: http://en.wikipedia.org/wiki/Ijiraq_%28moon%29

Norse Group Retrograde irregular

satellites Semi-major axes: 12-

42 x 106 km Inclinations: 136-175

degrees Eccentricities: 0.13-

0.77 Composed of > 4

subgroups– two i=174 subgroups– Skathi subgroup– Narvi subgroup

Image from: http://en.wikipedia.org/wiki/Saturn%27s_Inuit_group_of_satellites

Gallic Group Prograde irregular satellites Semi-major axes: 16-19 x

106 km Inclinations: 35-40 degrees Eccentricities: ~0.53 Spectral homogeneity

– Similar to Inuit Group– Break up of single object

4 members:– Albiorix– Bebhionn– Erriapus– Tarvos

Image from: http://en.wikipedia.org/wiki/Ijiraq_%28moon%29

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

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