Notes on Chapter 12: Rings, Moons, and Pluto

Learning Objectives:
- Name the major moons of each of the jovian planets.
- Describe the basic composition of each jovian planet’s ring system.
Composition of Rings and Moons:
- Outer solar system rings and moons are predominantly made of dark, organic compounds along with ice and rock.
- Approximately ⅓ of moons revolve counterclockwise (CCW) in the plane of their planet’s equator, while most have retrograde or highly eccentric orbits, likely captured by the planet.
Sizes of Moons:
- Small moons (< 300 km): No geological activity observed.
- Medium-sized moons (300–1500 km): Evidence of past geological activity.
- Large moons (> 1500 km): Currently exhibit ongoing geological activity.

Learning Objectives:
- Understand distinctive features of Jupiter's major moons (Callisto, Ganymede, Europa, and Io) and their geological activities.
Moons of Jupiter:
- Jupiter has 95 known moons and a faint ring.
- Callisto: Size similar to Mercury; heavily cratered with no tectonic activity due to lack of orbital heating.
- Ganymede: The largest moon, with some geological activity; features include dark, cratered areas and lighter, grooved terrain.
- Europa: Smooth surface with few craters, indicating a subsurface ocean potentially harboring life; features a layer of ice cracking revealing possible liquid water underneath.
- Io: The most volcanically active body in the solar system characterized by high silicate lava eruptions.
Tidal Heating:
- Tidal heating affects Io, Europa, and Ganymede, providing internal heat and leading to geological changes.
- Gravitational pulls from Jupiter lead to significant geological phenomena on these moons.

Learning Objectives:
- Discuss the properties of Titan's atmosphere and bodies of liquid existing on its surface.
- Analyze surface characteristics observed during Voyager 2's flyby of Triton.
Titan:
- Has a dense atmosphere (1.6 bar surface pressure); it experiences rain made of methane and ethane, indicating possible prebiotic conditions.
- Huygens Probe landed in 2005; surface temperature around 94 K (-290°F).
Triton:
- Features a thin atmosphere with geysers erupting nitrogen gas; retrograde orbit suggests it may have originated in the Kuiper belt.
- Surface composition includes frozen CO, nitrogen, and methane.

Learning Objectives:
- Compare Pluto's orbital characteristics to those of standard planets and describe geological features on Pluto and its moon Charon based on New Horizons findings.
Pluto:
- Composed similarly to comets; eccentric orbit at 39.44 AU from the Sun, mass approximately 1.2 x 10^22 kg.
- NOT classified as a planet; defined as a dwarf planet.
- New Horizons mission revealed diverse Terraria:
  - Cratered regions, vast plains, mountains composed of water ice, and a complex atmosphere with haze layers.
Charon:
- Diameter of about 1214 km with notable geological features.

Learning Objectives:
- Detail the theories of planetary ring formation and differentiate the properties of the rings from Saturn, Uranus, and Neptune.
Properties of Ring Systems:
- Jupiter: faint rings; composed of dust from moons.
- Saturn: prominent, bright rings made primarily of ice particles; gravitational interactions with moons contribute to the rings' structural features.
- Uranus & Neptune: Dark and narrow rings composed primarily of small particles with different characteristics compared to Saturn.
Ring Formation Theories:
1. Breakup Hypothesis: Rings formed from the remnants of a shattered moon.
2. Inability Hypothesis: Rings formed from particles that did not coalesce into moons originally.
Gravitational interactions with moons significantly impact the structures and appearances of these rings.