Jupiter-Like Planets

Jupiter-Like Planets

Outline

1. Appearances

* Clouds & storms

2. Insides

* Low density ==> light materials

* Jupiter & Saturn

> Liquid molecular & metallic hydrogen + rocky core

* Uranus & Neptune

> Liquid molecular hydrogen + 'slush' + rocky core

* Net radiation of heat

* Differential rotation

3. Magnetic Fields

* Fluid, conducting interiors + rapid rotation ==> strong fields

* Aurorae

4. Atmospheres

* Mainly hydrogen + helium (w/ methane & ammonia)

* Heated mainly from bottom

* High speed east-west winds

* Zones & belts

* Large cyclonic storms

* Galileo atmospheric probe

5. Moons

* Jupiter

> Io: extreme volcanism

> Europa: water beneath an icy crust?

> Ganymede: evidence of tectonics?

> Callisto: many craters

* Saturn

> Titan: smoggy atmosphere; Huygens probe

* Uranus

> Miranda: groovy terrain

* Neptune

> Triton: icy surface, thin atmosphere & geysers

6. Rings

* Particles orbiting a planet

* Jupiter: 'smoke'

* Saturn: ice & icy rock

* Uranus & Neptune: dark chunks

Questions

1. Compare and contrast the internal structures of Jupiter and Saturn with the internal structures of Uranus and Neptune. Can you propose an explanation for the differences between these two pairs of planets?

2. What is differential rotation? What evidence do we have that it occurs on Jupiter? What does differential rotation imply about Jupiter's interior?

3. What is responsible for the enormous magnetic fields of the Jovian planets?

4. Jovian planets have retained their original atmospheres, whereas terrestrial planets have not. What accounts for this difference?

5. What is the Great Red Spot?

6. What causes the belts and zones in Jupiter's atmosphere?

7. What gives Uranus and Neptune a distinctly blue color?

8. Why are numerous impact craters found on Ganymede and Callisto, but not on Io or Europa?

9. Why is there speculation that Europa might be an abode for life?

10. What evidence suggests tectonic activity on Ganymede?

11. Ques. #15, pg. 194.

12. What is unique about Miranda?

13. Where in the solar system do we find nitrogen geysers?

14. What are Saturn's rings made of?

15. What is the role of a 'Shepherd' moon?

16. What do the rings of Jupiter, Uranus and Neptune consist of?

Answers

1. Uranus & Neptune contain no liquid metallic hydrogen. Their lower masses do not raise the high internal pressures required for the conversion of liquid molecular hydrogen (which they do have) to the metallic form of hydrogen. Both Jupiter & Saturn contain both liquid molecular and metallic hydrogen. Both Uranus & Neptune do contain 'slush' (water?) zones, which are absent in Jupiter & Saturn.

2. Differential rotation means that a planet (or star) rotates with a different period at different latitudes. In the case of Jupiter, the rotation period is slightly shorter at the equator than near the poles. The implication is that the interior of Jupiter is (at least) partly fluid, as a solid body must rotate with the same period at all latitudes (e.g., like Earth, where the rotation period is 24 hours everywhere).

3. Enormous magnetic fields are raised by largely fluid interiors, high interior temperatures, and rapid rotation.

4. The difference is accounted for by i) much stronger gravity of the Jovian planets; ii) much lower temperatures at the Jovian planets. Strong gravity means high escape velocity; low temperature means low molecular speeds.

5. The GRS is a large rotating disturbance in Jupiter's atmosphere that resembles a cyclonic storm.

6. Belts and zones are created by a combination of vigorous convection in the interior, and rapid rotation.

7. The blue color results from methane gas in the atmospheres of these planets. Methane tends to absorb long-wavelength (red-orange) sunlight, leaving blues and greens behind.

8. Io is fantastically volcanically active; volcanic ejecta constantly deposited on the surface has obscured all evidence of impact cratering. Europa's ice appears to be renewed from time to time, perhaps by a deep water ocean lying beneath the ice. While ice does retain craters, these craters obviously disappear whenever the ice melts.

9. It's possible life could exist in an ocean under the surface ice (if such ocean exists). This life would have to be supported by local sources of energy (e.g., volcanic vents in the ocean bed), as little, if any, sunlight is likely to penetrate the ice.

10. Stretches of Ganymede's surface are covered by odd parallel grooves, which may result from compression of the crust - a tectonic disturbance.

11. Titan's atmosphere is remarkably dense (surface pressure about 1.5 times sea-level pressure on Earth); consists mainly of nitrogen; and is filled with a substantial haze (which resembles the photochemical smog generated over large cities on Earth). Telescopic images of Titan in the infrared show dark patches which may be oceans of liquid ethane, a substance which may be abundant on this world. We expect to learn much about Titan in 2004 as the Cassini mission will drop an atmospheric probe into Titan's atmosphere in that year.

12. Miranda's surface is partly covered by deep grooves, suggestive of tectonic activity. But such activity is unlikely on a body as small as Miranda (diameter = 300 miles), as bodies this small probably do not generate enough internal heat to support tectonics.

13. We find nitrogen geysers on the (icy) surface of Triton, the largest of Neptune's moons.

14. Saturn's rings very likely consist of chunks of ice and icy rock.

15. Shepherd moons act as 'ring wranglers,' keeping narrow rings narrow, preventing the ring particles from expanding into a broad ring, as the particles would like to do.

16. Jupiter: tiny particles, the size of smoke particles. Uranus: dark chunks of unknown composition. Neptune: dark chunks of unknown composition