Jovian Planets

What is the rotation period for the Jovian planets (Jupiter, Saturn, Uranus, Neptune)?

Between 10 to 20 hours, somewhat shorter than that of the Earth.

How does the mass of Jupiter compare to that of Earth?

About 300 times larger.

What characteristic features are seen on the visible surface of Jupiter?

Light and dark bands parallel to the equator.

When was the existence of the Great Red Spot of Jupiter known?

Since the time of Hooke and Cassini in the 1600s.

What is the estimated lifetime of the Great Red Spot of Jupiter?

At least 300 years, based on visual records.

What is the rotation period of Jupiter?

Relatively short, on the order of 10 hours.

What interesting feature is noted about Jupiter’s rotation?

Regions of Jupiter at different latitudes appear to rotate at different rates.

What is the composition of the clouds we see on Jupiter?

Similar to Earth’s clouds at lower levels (water droplets) and very different in higher levels (ammonia crystals and other chemicals).

How thick are the cloud layers on Jupiter’s visible surface?

About 60 km.

What is the expected interior structure of the Jovian planets?

Four-layered: a rocky core, a semifluid ice layer, a liquid mantle of hydrogen, and a gaseous hydrogen and helium atmosphere.

What is the temperature in the core of Jupiter?

Hotter than the Sun’s surface but cooler than the Sun’s core, so nuclear fusion cannot take place.

How powerful is Jupiter's magnetic field compared to Earth’s?

Much more powerful.

What material is thought to be responsible for Jupiter's powerful magnetic field?

Liquid metallic hydrogen.

What is the size of Jupiter's magnetosphere compared to the moon?

16 times larger than the full Moon.

What shape do the Galilean moons of Jupiter typically have?

Almost perfectly spherical.

What makes Io, a satellite of Jupiter, unique among known satellites?

It is volcanically active, with gas plumes and lava flows.

What is the surface of Europa, one of Jupiter's moons, covered with?

A smooth layer of ice crossed by many cracks.

What features dominate the surface of Ganymede?

Old, dark, highly cratered polygons separated by younger, lighter, grooved terrain.

What is the presumed structure of Callisto, a satellite of Jupiter?

A mixed ice-rock interior surrounded by a liquid ocean and then a solid icy crust.

How are the rings of Jupiter composed?

Made of material that is continually being ejected and replenished from Jovian moons.

What type of rings does Jupiter have?

Several thin dark rings made up of very fine dust particles.

What is the major composition of Saturn?

Composed primarily of liquids.

Why does Saturn's atmosphere lack colorful contrast?

Obscured by a thick hazy atmosphere despite similar circulation patterns to Jupiter.

What is Saturn's internal structure?

Rocky core, thick mantle of liquid metallic hydrogen and helium, relatively thin gaseous atmosphere.

In which plane do Saturn's rings exist?

Equatorial plane of Saturn.

What is the physical structure of Saturn's rings?

A sequence of many thousands of separate ringlets consisting of ice blocks and ice-coated rock.

What is a notable feature of Saturn's rings dimensions?

They are extremely thin compared to their lateral extent.

How do we see Saturn's rings?

By reflected and scattered sunlight.

How do particles in Saturn's rings move?

In circular Keplerian orbits; inner particles move fastest.

What is the Cassini division?

A wide, dark gap in Saturn’s rings.

Why is the F ring narrower than the main rings?

Two “shepherd” satellites focus the particles into a narrow ring.

What gravitational effects organize Saturn's ring particles?

Gravitational perturbations by the large moons orbiting these planets.

What makes Titan, Saturn's moon, unique among other moons?

It possesses a thick atmosphere.

What is the primary composition of Titan's atmosphere?

Mostly nitrogen, methane, and other hydrocarbons.

What feature does Enceladus probably NOT possess?

Molten lava flowing from active volcanoes.

What would Interplanetary Travel, Inc. advertise about Titan?

Exquisite ethane lakes, hydrocarbons beyond your wildest dreams, no shortage of fuel!

What is the surface temperature of Titan?

95 K (–178°C).

What chemical produces 'rain' on Titan?

Ethane, C2H6.

What are the most abundant gases in Uranus's atmosphere?

Hydrogen and helium, with traces of methane.

What causes Uranus to appear blue-green?

Absorption of red light by methane gas.

By what angle is Uranus's rotation axis tilted?

98°.

How are the expected seasonal changes on Uranus compared to Earth?

Very much exaggerated.

What is believed to be Uranus's interior structure?

Rocky core, thick liquid water layer, thick outer liquid hydrogen layer, and thin gaseous atmosphere.

How were the rings of Uranus discovered?

By occultation of light from a star as Uranus (and the rings) passed in front of it.

What are the characteristics of Uranus's rings?

Narrow and very dark.

In what plane do most Uranus satellites orbit?

In the plane of the planet’s equator, almost at right angles to the ecliptic.

What happened to Miranda, a satellite of Uranus?

It appears to have been reassembled from parts after being shattered by an impact.

How was Neptune discovered?

By applying Newton’s laws to the irregular motions of Uranus.

What is Neptune's appearance from space?

Blue-green with white, high-altitude clouds and dark storms.

What is the Great Dark Spot on Neptune?

A relatively short-lived storm system.

What causes Neptune's blue appearance?

Absorption of the red end of the spectrum by methane in its atmosphere.

What distinct feature differentiates Uranus from Neptune?

Uranus has an almost featureless visible image compared to Neptune's distinctly seen storms.

How are the magnetic fields of Uranus and Neptune oriented?

Tilted a long way from the spin axis of the planets.

Where do the magnetic fields of Uranus and Neptune originate?

In the liquid water-mineral mixture in the mantles of the planets.

What produces electric currents in Uranus and Neptune?

Molecules like ammonia (NH3), which become ionized in solution in water.

Does Neptune have a ring system?

Yes, a system of dark rings of particles coated in modified methane ice.

Why are Neptune's rings dark?

The particles are composed of methane ice that has darkened due to radiation damage.

What makes Triton unique among the moons of planets?

It orbits in a retrograde direction, opposite the planet’s rotation.

What features characterize Triton's surface?

Wrinkled surface, frozen lakes, and plumes of nitrogen gas.

What is a striking characteristic of Triton?

Plumes of nitrogen gas rising from the icy surface, possibly from radioactive heating.

What is the Roche limit?

The distance at which a planet creates tides on its moon’s surface high enough to pull it apart.