Astronomy Ch. 12 – Saturn

If you could find a bathtub big enough for Saturn, the planet would:

float.

Saturn’s rings are widest open, doubling the planet’s brightness, when it is at:

solstice.

Saturn’s rings are edge-on and vanish when it is at:

equinox.

The reason Saturn lost very little of its original atmosphere is due to its

large mass.

Saturn is noticeably oblate because

it is a fluid body that is spinning rapidly.

The atmosphere of Saturn is composed mostly of:

hydrogen and helium.

What is the space probe that is currently orbiting Saturn and is responsible for numerous discoveries of storms and weather patterns in Saturn’s atmosphere called?

Cassini.

The most abundant element in Saturn’s atmosphere is

hydrogen.

Compared to Jupiter, Saturn’s atmosphere is

more calm with fewer disturbances or storms.

Saturn’s cloud surface appears more uniform than Jupiter’s because

the cloud layers are thicker, allowing fewer holes to see the colorful layers.

The wind speeds found in the bands and zones of Saturn, compared to those on Jupiter, are about

3 times faster.

Compared to Jupiter, the motions observed in Saturn’s atmosphere are

faster with fewer zone-belt alternations.

Saturn’s bands, oval storm systems, and turbulent flow patterns are powered by:

convective motion and rapid rotation.

At the surface of Saturn’s atmosphere the strength of the magnetic field is

about the same as Earth’s magnetic field at its surface.

Why does the atmosphere of Saturn appear to have only half the helium content of Jupiter?

Much of Saturn’s helium has differentiated towards its center.

Why does Saturn radiate even more excess energy than Jupiter?

Helium rain gives off heat as it differentiates toward Saturn’s center.

What are Saturn’s rings?

small icy particles moving in orbit around Saturn

What did the Voyager mission discover about the main rings of Saturn?

They are composed of tens of thousands of narrow ringlets.

The reason the rings of Saturn exist is because:

the ring material lies within the Roche limit of Saturn.

The Roche limit is the point at which

the external tidal forces on an object become greater than the internal forces that hold it together.

Why are Saturn’s rings so noticeable?

They are made of lots of fresh, bright icy particles from a recent breakup.

Which of the following played the most important role in the ring’s formation?

Saturn’s Roche limit

Shepherd satellites are defined as:

moons that confine a narrow ring.

What did the Voyager mission discover about Cassini’s Division?

It contains several ringlets.

While Galileo saw Saturn as a changing oval, the real nature of the rings was discovered by:

Huygens.

A moon that goes inside the Roche Limit will

get heated by the strong magnetic fields.

The shepherd moons keep the ring particles in their rings by

attracting the ring particles, causing them to speed up or slow down.

When Voyager 2 was routed to fly by Saturn, it was originally the plan to have the satellite fly through the Cassini gap. Why would this have been a bad idea?

The gaps in Saturn’s ring system (including the Cassini gap) are not actually empty space, rather they are an area of low density in the rings.

If satellite A is in a 2:1 resonance with satellite B, this means that

the orbit of satellite B takes twice as long to complete as that of satellite A.

Why do scientists think the Cassini spacecraft did not observe "spokes" on the rings during the first year of its visit with Saturn?

To see the "spokes", a particular alignment of the rings with the Sun is necessary and it took one year for that alignment to reoccur.

Shepherd moons were discovered because scientists hypothesized their existence after observing

the narrow F Ring.

Cassini is:

a gap in the rings created by a resonance with Mimas. the French astronomer who first discovered a gap in Saturn’s rings. NASA’s orbiter now taking photos of Saturn. all of the above

How many large moons does Saturn have?

1

Rhea, Saturn’s second largest moon, might best be described as:

having a very reflective, icy surface that is heavily cratered.

Titan is an interesting moon because:

it has a rich atmosphere that may resemble that of the early Earth.

What evidence suggests that Enceladus has ongoing geological activity?

Lack of impact craters on much of its surface and evidence of ice flows from possible volcanic activity.

The atmosphere of Titan is composed mostly of:

nitrogen.

The asymmetrical surface markings on some of Saturn’s moons are probably due to:

in most cases, the moons are tidally locked by Saturn’s gravity into synchronous rotation.

How many medium-sized moons does Saturn have?

6

What is interesting about Saturn’s large moon Titan?

It has an atmosphere.

Why was it thought that Titan may have oceans of methane?

The atmospheric pressure at Titan’s surface and its surface temperature are such that methane should be liquid on Titan’s surface.

Why do scientists think Titan has an atmosphere while the large moons of Jupiter (Ganymede, Callisto, Europa and Io) do not?

The jovian satellites never formed atmospheres because the solar nebula was too hot there.

What did the Huygens and Cassini probes find on the surface of Titan?

an ocean of some unknown liquid and methane lakes

The "wispy terrain" on Rhea was revealed by the Cassini spacecraft to be

ice cliffs created by tectonic fractures.

The Cassini spacecraft found evidence that the E Ring is related to Enceladus through

a continual supply of icy particles spewed via volcanism on Enceladus.

Which Saturnian moon has the leading hemisphere black as tar, the back side icy white?

Iapetus

While not yet observed in eruption, it is likely that ________ has active volcanoes; it certainly has one hemisphere greatly reworked by tectonic and volcanic forces.

Enceladus

What mission landed on Titan in early 2005?

Huygens

What makes Mimas a distinct moon?

It suffered a huge meteorite impact that must have nearly shattered it.

Which moon of Saturn constantly changes its rotational speed and rotational axis?

Hyperion

In what two ways is Titan’s atmosphere like our own? Now name two differences. (SA)

Like the earth’s, Titan’s atmosphere is made chiefly of nitrogen, and it is at about the same barometric pressure as the earth at both surfaces. However, it is much colder, lacks any substantial oxygen, and its clouds are made of methane and other hydrocarbons, not water droplets like ours.

How is Mimas responsible for the Cassini Division? (SA)

Mimas has an orbital period precisely twice that of matter in the Cassini Division. As such, it exerts a regular tug on particles there, pulling them to an orbit further out. The particles stay in the outer orbit once they collide with other particles and lose excess energy.

How did scientists use Titan to guide Cassini on a tour of Saturn’s moon system? (SA)

Titan was used to give gravitational assists to increase and decrease the semi-major axis of the probe’s orbit. When Cassini passes Titan inside its orbit of Saturn, Cassini’s orbital semi-major axis is decreased. When Cassini passes Titan outside its orbit of Saturn, Cassini’s orbital semi-major axis is increased. Using this, Cassini’s controllers are able to guide the spacecraft on a tour of Saturn’s moon system even though the spacecraft doesn’t have much of its own power.

Describe the consequences of orbital resonances between the moons of Saturn and the particles that make up that planet’s ring system. (SA)

Particles that would have orbital periods which are integral fractions of lunar orbits are constantly pulled out of these orbits and into elliptical orbits. Through particle collisions, these orbits become circular again. Thus orbital resonances are effective in moving ring particles out of certain orbits and into others.