Download STUDY GUIDE FOR CHAPTER 1

STUDY GUIDE FOR CHAPTER 8
The following is a list of topics and subtopics along with some questions and explanations.
I.
The Jovian Planets
A. Differences with the terrestrial planets
1. location
2. size
3. rotation rates
a. Do they rotate faster or more slowly than the terrestrial planets?
b. What are the rotation rates?
4. composition
a. The Jovian planets are primarily composed of hydrogen, helium and hydrogen
compounds. What are the terrestrial planets primarily composed of?
b. moons. The Jovian planets have lots of moons. The terrestrial planets few or none.
B. Interiors
1. The outer layers of all Jovian planets are gaseous. They do not have surfaces.
2. As you go towards the center of a planet the density, temperature, and pressure increase.
a. Jupiter and Saturn
i. As you go down the gas gradually turns into a liquid (not all at once like on the
Earth where you have a well defined surface of a lake or ocean). The liquid is
liquid hydrogen.
ii.
Below this the hydrogen becomes metallic. That is, it conducts electricity.
iii.
Near the center is a core of rock, metal, and hydrogen compounds like water
and ammonia.
b. Uranus and Neptune
i.
We are less certain about the interiors of these planets. Again the outer
layers are gaseous.
ii.
As you go towards the interior the hydrogen stays a gas, but there may be an
area of liquid water and other hydrogen compounds.
iii.
In the center there is likely to be a core of rock and metal.
C. Atmospheres
1. The primary constituents of the planets atmospheres are hydrogen and helium
2. Convection occurs in the outer parts of each planet and the rapid rotation of the planet
results in a strong Coriolis force that expands the convection cells into bands that circle
the planet.
3. Jupiter
a. There are three layers of clouds.
i.
At the top of the cloud layer are clouds of ammonia ice crystals.
ii.
Farther down are clouds of ammonium-hydrosulfide crystals.
iii.
Farther down yet are clouds drops of water or water ice crystals.
b. Bands
i.
The white bands are regions where warm gas is rising. The white color is
due to ammonia ice crystals.
ii.
The brown and red regions are where the cool gas is falling. There are no
ammonia clouds and you see down to the ammonium-hydrosulfide clouds.
No one knows for sure where their red and brown colors come from.
c. Storms
i.
The great red spot is a high pressure storm two or three times the diameter of
the Earth that has been around for at least 300 years. No one is sure why it is
red.
ii.
White and brown ovals are smaller low pressure storms
4. Saturn
a. There are bands and the same three layers of clouds as in Jupiter’s atmosphere.
i.
They are deeper inside the atmosphere because Saturn is farther from the
Sun and so the lower temperature of the upper atmosphere results in these
clouds forming at a lower elevation.
ii.
A thicker layer of “smog” lies above the clouds than on Jupiter so they are
not as pronounced.
b. The types of storms are the same as on Jupiter but there is nothing comparable to the
great red spot.
5. Uranus
a. It is blue in color due to methane in its atmosphere.
b. It has bands like Jupiter and Saturn but they are much weaker and harder to see.
i. This may be due to less convection resulting from much less internal heat.
c. Clouds
i.
We see clouds made of methane ice crystals.
ii.
We don’t see any other types of clouds. If they exist they are too far down in
the atmosphere for us to see them.
6. Neptune
a. It is also blue in color due to methane in its atmosphere.
b. It has pronounced bands like Jupiter and Saturn but different in color.
c. The clouds we see are made of methane ice crystals.
d. There are storms. One high pressure region called the Great Dark Spot has now
disappeared. It was about the size of the Earth.
D. Magnetic Fields
1. Jupiter
a. Largest magnetic field in the solar system – 20,000 times as strong as Earth’s.
b. It is generated in the liquid metallic hydrogen region of its interior.
c. Because the field is so strong there are extensive radiation belts.
2. Saturn
a. It has a strong magnetic field but much weaker than Jupiter’s.
b. This is because it has a smaller region of liquid metallic hydrogen in its interior.
3. Uranus and Neptune
a. They both have magnetic fields that are offset from their rotation axes by a lot.
b. Their magnetic fields must be generated in their “oceans” of hydrogen compounds
(like water).
II.
Rings of the Jovian planets
A. General
1. Rings consist of many individual particles, each in a separate orbit about the planet.
2. Ring particles continually need to be replenished or the ring will disappear over long
periods of time like a billion years.
a. The particles can be knocked of small nearby moons as in the case of Jupiter’s ring.
b. They can occur if a small moon breaks up due to a collision with another object.
c. They can occur if a medium sized or large moon gets too close to a planet and is
broken apart by tidal forces.
3. Small moon in the rings cause particles near them to move to other orbits.
a. Each ring particle and each moon orbiting the planet obeys Kepler’s laws. Thus
those whose orbits are closer to the planet take less time to go once around than
those farther away.
b. The larger the orbit of an object the more total (kinetic plus gravitational potential)
energy it has.
c. If you have a small moon then ring particles that are close to it and inside its orbit
will catch up to it and pass it. The moon will exert an attractive force on these ring
particles that will slow them down as they pass by. This gives them less energy
and so they move into a lower orbit.
d. If ring particles are near to and outside of the orbit of a small moon then the moon
will catch up to them and pass them. It exerts an attractive gravitational force on
these particles and in the process of trying to pull them towards it, speeds them up.
Thus they gain energy and move out to higher orbits.
e. In this way a small moon can clear a gap in the rings. This is the case for the
Encke division in Saturn’s rings.
f. A small moon can also cause a ring to have a sharp edge. In the case of Saturn’s A
ring for example, a small moon orbits just outside the ring. Any ring particles that
try to spread out to higher orbits encounter it. As discussed in (c) above they are
shepherded to a lower orbit. This causes the ring to have a sharp outer edge.
g. Two small moons, one on each side of a narrow ring, can keep it narrow. If the
particles try to go to a lower orbit then the inner moon catches up with them and
passes them as in (d) and kicks them to a higher orbit. If they try to go to a higher
orbit then they catch up with and pass the outer moon and it kicks them into a
lower orbit as in c.
3. Gaps in rings can also be caused by orbital resonances. The Cassini division in
Saturn’s rings is one such case. If ring particles at a particular distance from the planet
(and thus with a particular orbital period) have periods that are some fraction of a
moon’s period particular distance from the planet, then the close approach between the
moon and the ring particles occurs periodically at the same part of their orbits. This is
the time when the moon exerts the strongest gravitational force on the ring particles
since it is closest to them. Since there is periodically a close approach in the same part
of the orbit the particles are always pulled at those times in the same direction by the
moon. Over time their orbits are distorted and a gap forms in the rings. If there is no
resonance the extra tug that occurs at close approach happens in random parts of the
orbit. In this case the tugs cancel out rather than adding up and nothing happens. Note
that for orbital resonances to occur the moon must be large enough and close enough to
exert a strong enough force on the ring particles to alter their orbits.
B. Jupiter
1. Has a faint ring.
2. What are the particles composed of?
C. Saturn
1. Has several rings.
a. The A and B rings are broad and bright and separated by the Cassini division.
b. The C ring is also broad but fainter and inside the B ring.
c. The F ring is narrow and looks like it is braided and twisted in places.
2. What are the ring particles mostly composed of?
D. Uranus
1. Has nine narrow dark rings
2. There is some dust between the rings.
3. The particles are probably ices that contain methane that has interacted with sunlight
and formed dark carbon compounds.
4. Most of the particles are larger than 1 cm in size.
E. Neptune
1. Has three narrow rings and one broader one plus a band that goes down to the
atmosphere.
2. The rings are dark like those of Uranus and may have similar particles.
3. One of the rings varies in density at different points.
III.
Moons of the Jovian planets
A. General
1. The book defines small moons as less than 300 km in diameter, medium sized moons as
between 300 and 1500 km in diameter, and large moons as greater than 1500 km in
diameter. What type of moon is the Earth’s moon? the moons of Mars?
2. You should know the general characteristics about the moons of each planet. These are
given below.
3. You should know the four Galilean moons of Jupiter by name and you should know the
interesting features of each. You should also know Saturn’s moon Titan by name and
by its features as well as Neptune’s moon Triton.
B. Jupiter
1. Io
a. Composed almost entirely of rock and some metal. The surface is young. There
are no impact craters.
b. What are the volcanoes on Io due to? You should understand this.
c. Sulfur and sulfur dioxide are emitted by the volcanoes.
i.
Sulfur not heated too much gives the yellow color of parts of this moon.
Sulfur heated somewhat gives the orange and red colors. Sulfur heated a lot
gives the blacd color.
ii.
Sulfur dioxide is emitted by the volcanos along with sulfur. The sulfur
dioxide condenses and falls back to the surface as snow, giving parts of it a
white color.
2. Europa
a. Composed primarily of rock and some metal but with a layer of ice and possibly
water 100 km thick.
b. There is good evidence that an ocean exists beneath the ice in this layer. If so could
there be life?
c. Tidal heating occurs but not as much as on Io because Europa is farther away.
3. Ganymede
a. The largest moon in the solar system. Larger than Mercury.
b. It is about half rock with some metal and half ice.
c. What surface features does it have that are unique?
d. It has a weak magnetic field. Could there be an ocean?
4. Callisto
a. About half rock with some metal and half ice.
b. A heavily cratered, very old surface.
c. It too has a weak magnetic field and thus perhaps an ocean under the surface. Since
there is no orbital resonance with the other Galilean moons and thus there should be
no tidal heating, it is a mystery as to why the interior should not be solid.
C. Saturn
1. General
a. Titan is the only large moon
b. All of the moons are composed mostly of ice and rock.
2. Titan
a. Second largest moon in the solar system and also is larger than Mercury.
b. It has the largest atmosphere of any moon and about 10 times as much material in
its atmosphere as Earth does. Because it is smaller, the atmospheric pressure is
only 1 ½ times as much as on Earth.
i.
ii.
The atmosphere is composed primarily of nitrogen.
There is a thick layer of smog that keeps us from seeing the surface. This is
probably due to sunlight interacting with various hydrocarbons in the
atmosphere.
c. At the surface methane can be a solid, liquid, or a gas. Thus it is like water on
Earth. Thus there could be methane clouds, methane rain or snow and even
methane rivers and oceans. Ethane can also be a liquid and there could be ethane
oceans. It is too cold for liquid water to be on the surface.
d. There is evidence from a spacecraft that landed on the surface and took pictures that
there are river valleys and there is evidence from radar mapping of the surface for
lakes of liquid ethane or methane.
3. A small moon (Enceladus) has geysers of water vapor and ice particles
D. Uranus
1. There are no large moons but there are several medium sized and small moons.
2. They are all dark, probably due to various carbon compounds on their surfaces.
3. They are made of ices and rock. The ices can include ammonia and methane as well as
water.
4. One medium sized moon has a very strange, jumbled shape. It may have been broken
apart by a collision and them come back together.
E. Neptune
1. There is one large moon, Triton and several small ones.
2. Triton
a. It is somewhat larger than Pluto.
b. It is composed of ice and rock.
c. It has a thin atmosphere composed mostly of nitrogen.
d. It has some very peculiar terrain that looks like the skin of a cantaloupe.
e. There are streaks of dark material that have been blown by the wind.