Moons of the Jovian Planets Module 5

Module 5: Moons of the Jovian Planets

Moons of Jovian Planets – Number of Moons

  • Jupiter: 64 moons

  • Saturn: 53 moons

  • Uranus: 27 moons

  • Neptune: 13 moons

Categories of Moons by Size

  1. Large Moons (6 Total)

    • 2500 km diameter

    • Have their own geology and history

    • About the same size as the Earth’s Moon

  2. Medium Moons (12 Total)

    • Diameter between 400-1500 km

    • Spherical and heavily cratered

  3. Small Moons (Many)

    • <300 km diameter

    • Irregular shape

    • Mostly made of ice

    • Trapped by gravity

    • Continuously being discovered

The Galilean Moons of Jupiter

  • Moons: Io, Europa, Ganymede, Callisto

  • Named after Galileo, who discovered them

  • Orbits:

    • Circular and prograde

    • Wider orbits the further they are from Jupiter

Characteristics of Jupiter’s Four Large Moons

  • Size Comparison:

    • Europa: smaller than Earth’s Moon

    • Ganymede: larger than Mercury

  • Densities: Decrease outward, simulating solar system formation

  • Findings from Galileo spacecraft:

    • Io and Europa: Cores are iron; large rocky mantles

    • Europa: Water/ice crust (100-200 km thick)

Interiors of Ganymede and Callisto

  • Ganymede and Callisto share similarities:

    • Lower density with water ice

    • Ganymede:

      • Small metallic core

      • Rocky mantle

      • Ice shell with possible water

    • Callisto:

      • Mixture of rock and ice with no distinct layers

Io: The Volcanically Active Moon

  • Most geologically active object in the solar system

  • Surface Features: Orange, yellow, black colors, craters

  • Active Volcanoes: Discovered by Voyager 1, including Prometheus

    • Plumes reaching up to 150 km at velocities of 2 km/s

    • Surface primarily smooth, filled with molten materials

  • Atmosphere: Thin, composed of sulfur dioxide

Io's Geological Dynamics

  • High Activity: 80 active volcanoes, including Loki, the largest

  • Temperature Range: Lava temperatures between 650-900K, up to 2000K

Io’s Heating Mechanism

  • Unexpected Activity: Initially expected to be inactive

  • Heat Source: Strong tidal forces from Jupiter’s gravity

  • Tidal bulges (100m) caused by interactions with neighboring moons (e.g., Europa)

  • Tidal stresses create heat, resulting in volcanic activity

    • Energy output: 100 million megawatts, 5x global consumption

Europa: Potential for Life?

  • Surface Features:

    • Few craters; water ice with lines cut through

    • Possible liquid ocean beneath the icy surface (100 km deep)

  • Galileo Mission Discovery: Cracks filled with ice show active surface

Europa’s Tidal Heating and Interior

  • Similar to Io, but less intense tidal heating

  • Magnetic Field: Weak and variable, created by interactions with Jupiter’s magnetic field and salty liquid water

Ganymede: Largest Jovian Moon

  • Larger than Mercury, characterized by a fractured icy surface

  • Geological Features:

    • Global ocean beneath the surface

    • Light and dark areas indicate age and geological activity

Callisto: Impact History and Surface

  • Similar to Ganymede but older, with more impact craters

  • Not active currently, with a frozen structure lacking layers

Titan: Saturn’s Largest Moon

  • Notable for its dense atmosphere (60% thicker than Earth’s)

  • Composition: Mostly nitrogen with methane and trace gases

  • Surface temperature: 94K, facilitates strange liquid cycles (methane and ethane)

Titan’s Atmosphere and Surface Features

  • Atmospheric structure with unique haze layers, reflection of UV light

  • Geologically active surface with icy features and few craters

Triton: Neptune's Unusual Moon

  • Unique Features: Retrograde orbit, thin atmosphere, surface geysers of liquid nitrogen

  • Likely a captured object from the Kuiper Belt, with significant geological history

Medium-sized Moons of the Jovian Planets

  • Total of twelve:

    • 6 at Saturn, 5 at Uranus, 1 at Neptune

    • Characteristics: radius between 200-800 km, old and heavily cratered surfaces, little geological activity

Saturn’s Medium-sized Moons

  • Rhea and Dionne: Light, wispy terrain with possible ice involvement

  • Mimas and Tethys: Impact craters and volcanic features

  • Iapetus: Two-tone appearance and influence from a ring of material

  • Enceladus: Brightest surface; features geysers and young geological activity

Uranus’ Medium-sized Moons

  • Includes Ariel, Titania, Oberon, Umbriel, which are heavily cratered with minor geological signs

  • Miranda: Notable for its ridges and valleys, suggesting past collisions.