Transcript 1. Differential Rotation

1. Helium rain
• lower temperatures of Saturn's interior
allow helium to come out of solution with
hydrogen and form droplets, these droplets
fall toward the center of Saturn depleting
the outer layers of helium and producing the
excess heat that is radiated by Saturn.
2. Tidal stability limit
• the distance from a planet within which a
moon will be torn apart by the gravitational
pull, believed to be the cause of the rings of
the Jovian planets, also called the Roche
limit.
3. Roche limit
• --the distance from a planet within which a
moon will be torn apart by the gravitational
pull, believed to be the cause of the rings of
the Jovian planets, also called the tidal
stability limit.
4. ringlets
• smaller rings that actually make the ring
structure of Saturn, discovered by the
Voyager spacecraft, numbering in the tens
of thousands.
5. Ring gaps
• areas of very little or no ring material
between the rings
6. moonlets
• small moons that scoop up ring material as
the moon moves through its orbit leaving a
gap in its wake
7. resonance
• repeated gravitational pull in certain areas
of the ring by small moons (Mimas, for
example) that produces gaps in the rings
8. shepherd satellites
• -the two small moons which keep the F-ring
in place, Prometheus and Pandora
9. spokes
• dark lines extending outward through the
rings, caused by small particles suspended
above the plane of the rings
10. Titan
• largest moon of Saturn, has an atmosphere
11. Odysseus
• huge impact crater on Tethys
12. wispy terrain
• prominent, light-colored streaks on trailing
face of Rhea
13. Cassini regio
• dark area on leading face of Iapetus
14. F-ring
• thin, braid-like ring held in place by
shepherd satellites
15. coorbital satellites
• Janus and Epimethius, have the same orbit,
one slightly closer to Saturn than the other;
every 4 Earth years they switch places
16. LaGrange points
• points where smaller moons accompany
larger moons in their orbits, 60 degree
angles to the larger moon
17. chaotic rotation
• orbit of Hyperion, because of gravitational
pull of Saturn and Titan the orbit is not
circular; moon constantly changes rotational
speed and and axis
1. Why is Saturn's polar radius
shorter than its equatorial
radius?
• Saturn has a low density and a high rotation
rate. This causes Saturn to be flattened.
The term for this is oblateness.
2. Which two elements make up
most of Saturn? How does this
compare to Jupiter?
• Hydrogen and Helium, same as Jupiter.
3. Why is Saturn's surface
appearance so much more
uniform than Jupiter's?
• Saturn's weaker gravity results in a thicker
atmosphere, so holes in the upper atmosphere
don't show the lower darker layers as on
Jupiter.
4. What is similar about all the
Jovian planets?
• They are all gas giants, and they all have
rings.
5. What is the tidal stability
limit (Roche limit)?
• The distance from a planet within which a
moon will be torn apart by the gravitational
pull of the planet.
6. List two ways Saturn's moons
affect Saturn's rings.
• Some moons sweep through the rings
plowing out gaps. Other moons produce
gaps due to gravitational pull on the rings.
7. What are shepherd satellites?
• Two moons (Prometheus and Pandora) that
form the "braided" F-ring.
8. How many rings are there?
• Tens of thousands of narrow ringlets.
9. What is unique about Titan,
Saturn's largest moon?
• It has an atmosphere.
10. List Saturn's medium sized
moons.
•
•
•
•
•
•
Mimas
Enceladus
Tethys
Dione
Rhea
Iapetus
11. What is unique about the
orbits of Hyperion and Phoebe?
• Hyperion has a chaotic orbit because of
Titan's gravity, constantly changing its
rotation speed and axis.
• Phoebe is Saturn's only moon with a
retrograde orbit.
12. Describe the orbits of Janus
and Epimethius.
• They are coorbital satellites. One is slightly
closer to the planet, so it orbits slightly
faster. When the inner moon "laps" the
outer one, they switch places.