AST101 CHAPTER 11

Which of the following gases is not a significant ingredient of the jovian planet atmospheres?

carbon dioxide Carbon dioxide is important in the terrestrial planet atmospheres, but not in the jovian planet atmospheres.

Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?

They actually contain relatively little material in a gaseous state. Much more of their mass is liquid, metallic, or in strange high-pressure states that we don’t naturally find on Earth.

According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?

Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula. Based on this idea, larger planets might have formed if the solar nebula had taken longer to clear.

Which of the following most likely explains why Jupiter’s interior releases so much heat?

Jupiter is contracting very gradually. This contraction would be too small for us to measure with current technology, but would be sufficient to convert enough gravitational potential energy into thermal energy to explain our observations.

What would happen to Jupiter if we could somehow double its mass?

Its density would increase but its diameter would barely change. You can understand why by thinking about the pillow stack analogy described in Section 11.1 of The Cosmic Perspective.

Which planet may have helium rain in its interior, and what does this rain do?

Saturn, where it generates heat as it falls downward. Models suggest that this helium rain may explain Saturn’s internal heating.

Why does Jupiter have three distinct layers of clouds?

The three layers represent clouds made of gases that condense at different temperatures. The three cloud layers are ammonia, ammonium hydrosulfide, and water. Each of these gases condenses at a different temperature and hence at a different altitude in Jupiter’s atmosphere.

Which of the following best explains why we see horizontal "stripes" in photographs of Jupiter and Saturn?

The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds. And the reason these stripes stretch all the way around these planets is the strong Coriolis force that comes from the planets’ rapid rotation.

Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?

Temperatures on Jupiter and Saturn are too high for methane to condense. But methane can condense on Uranus and Neptune because they are farther from the Sun and hence colder.

Which jovian planet should have the most extreme seasonal changes?

Uranus Its large axis tilt gives it seasons that each last about ¼ of its 84-year orbit.

Why is the radiation so intense in the region that traces Io’s orbit around Jupiter (the Io torus)?

The region is full of gases that become ionized after they are released from volcanoes on Io. Io’s low gravity allows these gases to escape.

Which statement about Saturn’s rings is not true?

The rings must look much the same today as they did shortly after Saturn formed. Ring particles cannot last long compared to the age of the solar system, so the rings much change their appearance with time.

All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io?

Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites. On an elliptical orbit, tides vary and flex Io’s shape.

Why do astronomers believe that Triton is a captured moon?

Triton orbits Neptune in a direction opposite that of Neptune’s rotation. This "backward" orbit is a tell-tale sign of a captured moon.