Chapter 8 Moons, Rings, and Plutoids

Copyright © 2010 Pearson Education, Inc.Copyright © 2010 Pearson Education, Inc.

Chapter 8 Moons, Rings, and Plutoids

Copyright © 2010 Pearson Education, Inc.

Chapter 8Moons, Rings, and Plutoids


Units of Chapter 8The Galilean Moons of JupiterThe Large Moons of Saturn and NeptuneThe Medium-Sized Jovian MoonsPlanetary RingsBeyond NeptunePlutoids and the Kuiper Belt


As their distance from Jupiter increases, the four Galilean satellites show a consistent

Question 1

a) increase in density.b) increase in size.c) decrease in cratering.d) decrease in density.e) amount of cratering.


As their distance from Jupiter increases, the four Galilean satellites show a consistent

Question 1

a) increase in density.b) increase in size.c) decrease in cratering.d) decrease in density.e) amount of cratering.

Like a miniature version of our solar system, Jupiter’s four large moons

show a decrease in density as distance increases. Io is most dense of the four;

Callisto is least dense.


The Galilean Moons of JupiterAll four Jovian planets have extensive moon systems, and more are continually being discovered.The Galilean moons of Jupiter are those observed by Galileo: Io, Europa, Ganymede, and Callisto.


The Galilean Moons of JupiterThis image shows Jupiter with two of its Galilean moons.

Galilean Moons


The Galilean Moons of Jupiter

The Galilean moons and their orbits


The Galilean Moons of JupiterTheir interiors


The Galilean Moons of JupiterIo is the densest of Jupiter’s moons, and the most geologically active object in the solar system.• It has many active volcanoes, some quite

large.• Io can change surface features in a few

weeks.• Io has no craters; they fill in too fast – Io has

the youngest surface of any solar system object.


What is thought to cause Io’s volcanism?

Question 3

a) Jupiter’s magnetosphereb) Jupiter’s rapid rotationc) tidal stress from Jupiter and Europad) radioactive decay from its coree) Io’s large mass and tectonic activity


What is thought to cause Io’s volcanism?

Question 3

a) Jupiter’s magnetosphereb) Jupiter’s rapid rotationc) tidal stress from Jupiter and Europad) radioactive decay from its coree) Io’s large mass and tectonic activity

Io is constantly “squeezed” by its huge neighbor as well as by

companion moons, heating its interior.


The Galilean Moons of Jupiter

Io is very close to Jupiter, and also experiences gravitational forces from Europa. The tidal forces are huge, and provide the energy for the volcanoes.

Io Cutaway


The surface of which jovian moon most resembles the pack ice of the Arctic Ocean?

Question 2

a) Europa b) Ioc) Amalthead) Ganymedee) Callisto


The surface of which jovian moon most resembles the pack ice of the Arctic Ocean?

Question 2

Ice-filled surface cracks

indicate an ocean may lie below.

a) Europab) Ioc) Amalthead) Ganymedee) Callisto


The Galilean Moons of JupiterEuropa has no craters; surface is water ice, possibly with liquid water below.Tidal forces stress and crack ice; water flows, keeping surface relatively flat.

Galileo’s View


The Galilean Moons of JupiterGanymede is the largest moon in the solar system – larger than Pluto and Mercury.It has a history similar to Earth’s Moon, but with water ice instead of lunar rock.

Galileo’s View


The Galilean Moons of JupiterCallisto is similar to Ganymede; no evidence of plate activity.


The Large Moons of Saturn and Neptune

Titan has been known for many years to have an atmosphere thicker and denser than Earth’s; mostly nitrogen and argon.

Makes surface impossible to see; the picture at right was taken from only 4000 km away.

Saturn Moon



Infrared image of Titan, showing detail, and possible icy volcanoFew craters, consistent with active surfaceComplex chemical interactions in atmosphere


The Huygens lander took these images of the surface of Titan.


Huygens Probe



Trace chemicals in Titan’s atmosphere make it chemically complex.


The Large Moons of Saturn and NeptuneTriton is in a retrograde orbit; its surface has few craters, indicating an active surface.

Nitrogen geysers have been observed on Triton, contributing to the surface features.


The Medium-Sized Jovian MoonsDensities of these moons suggest that they are rock and water ice.


The Medium-Sized Jovian MoonsMoons of Saturn, in natural color

Note the similarities, as well as the large crater on Mimas.


The Medium-Sized Jovian MoonsMoons of Uranus and Neptune


The Medium-Sized Jovian MoonsMiranda shows evidence of a violent past, although the origin of the surface features is unknown.


Question 8

a) our Moonb) Phobosc) Europad) Titane) Triton

Which moon in the solar system shows a dense atmosphere?


Question 8

a) our Moonb) Phobosc) Europad) Titane) Triton

Which moon in the solar system shows a dense atmosphere?

The Huygens probe, deployed by the Cassini spacecraft in 2005,

showed that Titan’s atmosphere has a complex organic chemistry.


Planetary RingsThe ring system of Saturn is large and complex, and easily seen from Earth. The other Jovian planets have ring systems as well.


Which of these moons are most exciting to exobiologists?

Question 13

a) Io and Enceladusb) Titan and Europac) Titan and Tritond) Europa and Mirandae) Phobos and Deimos


Which of these moons are most exciting to exobiologists?

Question 13

a) Io and Enceladusb) Titan and Europac) Titan and Tritond) Europa and Mirandae) Phobos and Deimos

Europa has indications of liquid water beneath the ice.

Titan shows evidence of

channels under its dense

atmosphere.


Planetary RingsThe rings are not solid; they are composed of small rocky and icy particles.


Planetary Rings

Our view of Saturn’s rings changes as the planets move in their orbits.


Why are the rings of Saturn so bright?

Question 7

a) They are made of frozen metallic hydrogen.b) They contain glassy beads expelled by

volcanoes on Enceladus.c) They contain shiny bits of iron.d) Titan and other moons reflect additional

glow onto the rings. e) They are made of relatively new ice.


Why are the rings of Saturn so bright?

Question 7

a) They are made of frozen metallic hydrogen.b) They contain glassy beads expelled by

volcanoes on Enceladus.c) They contain shiny bits of iron.d) Titan and other moons reflect an additional

glow onto the rings. e) They are made of relatively new ice.

Saturn’s rings are perhaps only 50 million years old, the result of a small moon coming within the planet’s

Roche limit.


Planetary RingsThe Roche limit is where the tidal forces of the planet are too strong for a moon to survive; this is where rings are formed.


The Roche limit is defined as the critical

Question 5

a) distance from a planet, inside of which a moon can be tidally destroyed.

b) density that a moon can have and be solid.c) distance from a planet that a moon can

experience synchronous rotation.d) mass a moon can have and still be

classified as a moon.


The Roche limit is defined as the critical

Question 5

a) distance from a planet, inside of which a moon can be tidally destroyed.

b) density that a moon can have and be solid.c) distance from a planet that a moon can

experience synchronous rotation.d) mass a moon can have and still be

classified as a moon.

Saturn’s rings, as well as those of the other jovian planets, lie within its planet’s Roche limit.


Planetary RingsAll observed ring systems are within this limit.


Planetary RingsVoyager probes showed Saturn’s rings to be much more complex than originally thought.

Earth is shown on the same scale as the rings.

Ring Crossing


Planetary Rings“Shepherd” moons define the edges of some of the rings.


Cassini Spacecraft

http://www.dailymail.co.uk/sciencetech/article-1172205/Saturn-close-Sensational-cosmic-images-bring-ringed-planet-life.html


Shepherd satellites are defined as

Question 6

a) satellites in the coma of a comet.b) moons that confine a narrow ring.c) a type of moon that orbits another moon.d) moons that share an orbit of another,

larger moon.e) moons that orbit inside a system of rings.


Shepherd satellites are defined as

Question 6

a) satellites in the coma of a comet.b) moons that confine a narrow ring.c) a type of moon that orbits another moon.d) moons that share an orbit of another,

larger moon.e) moons that orbit inside a system of rings.


Planetary RingsJupiter has been found to have a small, thin ring.


How was the ring of Jupiter discovered?

Question 4a) by optical telescopic observers from Earthb) by Voyager I as it passed Jupiterc) by an occultation of a stard) by radar imaging using the Arecibo dishe) with the Hubble Space Telescope’s superior

resolution


How was the ring of Jupiter discovered?

Question 4a) by optical telescopic observers from Earthb) by Voyager I as it passed Jupiter c) by an occultation of a stard) by radar imaging using the Arecibo dishe) with the Hubble Space Telescope’s superior

resolution

Jupiter’s ring is composed of dark, dusty particles that were first seen when Voyager was past the planet, looking back toward the Sun.


Planetary RingsThe rings of Uranus are more complex.


Planetary RingsTwo shepherd moons keep the epsilon ring from diffusing.


Planetary RingsNeptune has five rings, three narrow and two wide.


The rings of Neptune

Question 10a) were confirmed by Voyager 2 in 1989.b) appear both narrow and diffuse.c) all lie within Neptune’s Roche limit.d) often appear as clumpy ring arcs, rather

than complete and symmetrical rings.e) All of these are correct.


The rings of Neptune

Question 10a) were confirmed by Voyager 2 in 1989.b) appear both narrow and diffuse.c) all lie within Neptune’s Roche limit.d) often appear as clumpy ring arcs, rather

than complete and symmetrical rings.e) All of these are correct.


Beyond NeptunePluto was discovered in 1930. It was thought to be needed to explain irregularities in the orbits of Uranus and Neptune, but it turned out that there were no such irregularities.


Beyond NeptunePluto’s moon, Charon, was discovered in 1978.It is orbitally locked to Pluto, and about a sixth as large.Pluto also has two smaller moons, Nix and Hydra, discovered in 2005.


Question 12a) a cold terrestrial planet.b) a small jovian planet.c) a large Kuiper belt object.d) a wandering moon.e) a captured comet.

Many astronomers believe Pluto is perhaps best classified as


Many astronomers believe Pluto is perhaps best classified as

Question 12a) a cold terrestrial planet.b) a small jovian planet.c) a large Kuiper belt object.d) a wandering moon.e) a captured comet.

Several other large Kuiper belt objects

have been discovered, including the largest known, called Eris.


Beyond NeptuneCharon’s orbit is at a large angle to the plane of Pluto’s orbit.


Astronomy for $100

What is a celestial body that

(a) is in orbit around the Sun

(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape

(c) has cleared the neighborhood around its orbit


What is a planet?


Plutoids and the Kuiper BeltThe first Kuiper belt objects were observed in the 1990s, and more than 700 are now known. Some of them are comparable in size to Pluto. These images show Eris and its moon Dysnomia.


Plutoids and the Kuiper BeltThis figure shows several of the largest known trans-Neptunian objects, now collectively called plutoids.

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Chapter 8 Moons, Rings, and Plutoids