2012 Week 7 Objectives
10-3
1. Jupiter’s Galilean satellites are easily seen with Earth-based telescopes. Gravitational
interactions between Io, Europa, and Ganymede induce a rhythmic relationship among their
orbits.
2. Data from spacecraft reveal the unique properties of the Galilean satellites. Three of the
Galilean satellites are made of a mixture of ice and rock; only Io is ice-free.
3. The Galilean satellites formed like a solar system in miniature. The differences in composition
among the Galilean satellites mimic those among planets orbiting the Sun.
4. Io is covered with colorful sulfur compounds ejected from active volcanoes. The theory of
tidal forces helped predict Io’s volcanic nature.
5. Jupiter’s magnetic field makes electric currents flow in Io’s molten interior. Jupiter and Io
together act like an immense electric generator. The interaction produces the Io Torus.
6. Europa is covered with a smooth layer of ice that may cover a worldwide ocean. Geology on
Europa is based on solid ice and liquid water, not on rock and molten magma.
7. Liquid water may also lie beneath the cratered surfaces of Ganymede and Callisto. Both
Ganymede and Callisto show evidence of past geologic activity.
8. Titan has a thick, opaque atmosphere rich in methane, nitrogen, and hydrocarbons. A faint
mist of methane rain falls continually on Titan.
9. Jupiter has dozens of small satellites that have different origins. Only a few of Jupiter’s
satellites orbit the planet in the same direction as Jupiter rotates.
10. The icy surfaces of Saturn’s six moderate-sized moons provide clues to their histories.
Although just 500 km across, Enceladus has powerful water volcanoes at its south pole.
11. Jupiter and Saturn are the most massive planets in the solar system. Even a small telescope
reveals colored bands on Jupiter and rings around Saturn.
12. Unlike the terrestrial planets, Jupiter and Saturn exhibit differential rotation.
Spacecraft observations were needed to determine the compositions of Jupiter and Saturn.
13. Spacecraft images show remarkable activity in the clouds of Jupiter and Saturn
Immense storms on Jupiter and Saturn can last for months or years.
14. The internal heat of Jupiter and Saturn has a major effect on the planets’ atmospheres
Each planet radiates more energy into space than it receives from the Sun and each planet has
unusual and complex circulation patterns in its atmosphere.
15. The oblateness of Jupiter and Saturn reveals their rocky cores. Each planet’s rocky core is
surrounded by an outer core of liquid “ices,” a layer of helium and liquid metallic hydrogen, and
a layer of helium and ordinary molecular hydrogen (H2).
16. Metallic hydrogen inside Jupiter and Saturn endows the planets with strong magnetic fields.
Both Jupiter and Saturn have magnetospheres that are millions of kilometers across.
17. Saturn’s rings are composed of numerous icy fragments, while Jupiter’s rings are made of
small rocky particles. Tidal forces prevent the material of Saturn’s rings from coalescing into a
moon.
18. Saturn’s rings consist of thousands of narrow, closely spaced ringlets.
19. Saturn’s inner satellites affect the appearance and structure of its rings.
Gravitational effects carve gaps in the rings and focus ring particles into narrow ringlets
10-1
20. Viewing Mercury is difficult because it is so close to the Sun; Venus is easier to see but covered with
clouds; Mars is best seen at opposition.
21. While Mars rotates much like the Earth, Mercury’s rotation is coupled to its orbital motion and
Venus’s rotation is slow and retrograde. Radar technology revealed the curious rotation of Mercury and
Venus.
22. Mercury is cratered like the Moon but has a surprising magnetic field. Spacecraft observations at close
range were necessary to reveal Mercury’s unusual properties.
16. The first missions to Venus and Mars demolished decades of speculations about those planets
Venus was once thought to be steamy and tropical, and Mars was thought to have vegetation that varied
with the seasons.
23. Both Venus and Mars have volcanoes and craters—but no Earthlike plate tectonics. Venus has no
true plate tectonics because its crust is too thin. It does however possess mild tectonic activity. Know the
theory of “flake tectonics”. Mars’ crust is too thick.
24. The dense atmosphere of Venus and the thin Martian atmosphere are dramatically different but have
similar chemical compositions. On Venus, sulfuric acid rain evaporates before reaching the ground; on
Mars, it snows frozen carbon dioxide.
25. The atmospheres of Venus and Mars were very different billions of years ago. The early atmospheres
of Earth, Venus, and Mars were predominantly water vapor and carbon dioxide.
26. Rovers have found evidence of ancient Martian water. Parts of Mars are far drier than a bone, while
others had standing water for extended periods.
27. The two Martian moons resemble asteroids.