Jupiter and Saturn Lecture Review

Ganymede
- Third and largest of the Galilean satellites.
- Largest moon in the solar system, larger than Mercury but has less than half its mass.
- Unique as it generates its own magnetic field.
- Composed of approximately 50% rock and 50% water ice by mass; has no significant atmosphere.
- Interior fully differentiated with a subsurface ocean similar to Europa.
Callisto
- Fourth of the Galilean moons; does not participate in the orbital resonance with Io, Europa, and Ganymede.
- Simulations suggest it may eventually be forced into a 1:2:4:8 resonance.
- Heavily cratered, indicating an old surface; partially differentiated with no clear core/mantle, suggesting limited heating during formation.

Exploration Missions
- Pioneer 10: First close flyby of Jupiter, reached solar escape velocity; carried a gold "greeting card".
- Voyager 1 & 2: Conducted tours of the solar system, gathering crucial data.
- Galileo: Orbited Jupiter from 1995-2003, providing extensive data about the planet's atmosphere and moons.
- Juno: Currently in orbit (since 2016) providing detailed information about Jupiter's magnetic field and atmosphere.
- Europa Clipper: Scheduled to study Europa's interior in detail, after passing Mars in 2025 and returning to Earth in 2026, with an expected arrival at Jupiter in 2030.

Saturn vs. Jupiter
- Saturn's atmospheric layers are deeper due to its lower temperatures compared to Jupiter.
- Uranus and Neptune have different gas compositions resulting from their colder temperatures, leading to distinct cloud formations.
Jupiter's Great Red Spot
- A long-lasting storm at least 150 years old, possibly up to 400.
- Drags red gas from the interior to the surface, affecting its coloration.
- Location stable but the storm wanders East/West, size varies over time.

Overview
- Sixth planet from the Sun; slightly smaller than Jupiter but only 1/3 its mass.
- Has approximately 150 known moons; a recent paper suggested up to 274.
- Most extensive ring system of any planet in the solar system.
Observational History
- Galileo observed Saturn in 1610, mistaking its rings for moons.
- Christian Huygens improved this understanding in 1659 with better telescopes and discovered Titan, Saturn's largest moon.
Saturn's Atmospheric Phenomena
- Great White Spots: Similar to Jupiter's Great Red Spot but short-lived and recurs every Saturn year during the summer solstice.
- North Pole Hexagon: A stable hexagonal shape around the north pole that influences atmospheric dynamics; recreated in lab conditions.

Overview
- Titan is tidally locked to Saturn; the second largest moon in the solar system.
- Accounts for 95% of all mass orbiting Saturn; unique for its dense atmosphere with a surface pressure 1.5 times that of Earth.
- Composition includes nitrogen, methane, and hydrogen; has clouds of hydrocarbons that are opaque to visible light.
Surface and Climate
- Extremely cold surface temperatures of about -180^{ ext{°C}} (or about -300^{ ext{°F}}).
- Has lakes and rivers, but they consist of liquid ethane and methane, as water would be frozen.
- Features include cryovolcanoes which expel a mix of water, methane, and ethane instead of lava.
- The Kraken Mare is the largest sea on Titan, comparable in area to Earth's Black Sea, though its depth is unknown.
Exploration
- Cassini-Huygens Mission: Cassini orbited Saturn while Huygens landed on Titan, revealing extensive data about Titan's surface and atmosphere.

Overview
- Enceladus is about 1/10th the size of Titan.
- Features “Tiger Stripes” indicating geological activity; a sub-surface ocean may exist beneath its icy surface,
- Cryovolcanism on Enceladus ejects material into orbit, contributing to Saturn’s rings.

Differentiation: The process of forming distinct layers within a planetary body; relevant in discussing the composition and structure of moons like Ganymede and Callisto.
Coriolis Effect: A key factor in atmospheric dynamics on gas giants.