Introduction of Jovian planets

Introduction to Jovian Planets

• Jovian planets: Jupiter, Saturn, Uranus, and Neptune.

• Detailed knowledge primarily gained from spacecraft rather than ground-based telescopes.

• Importance of various missions to explore these planets.

Key Spacecraft Missions

• Voyager Missions (1970s)

  • Voyager 1: Explored Jupiter and Saturn.

  • Voyager 2: Explored Saturn, Uranus, and Neptune.

  • Conducted studies on electromagnetic (EM) fields and used different fields of light (radio, visible, infrared).

  • Returned valuable data for analysis.

• GALILEO Mission

  • Launched in the late 1980s, arrived at Jupiter in the mid-1990s.

  • Equipped with an atmospheric sensor to study Jupiter's atmosphere and its moons (detailed in Chapter 8).

• Cassini Mission

  • Launched in the late 1990s, focused on Saturn and its moon Titan.

  • Continues to operate, studying the planet, rings, and moons.

Comparative Characteristics of Jovian Planets

• Size and Mass Comparison

  • Jovian planets are significantly larger and more massive than Earth.

  • Earth as a baseline: mass = 1, radius = 1.

  • Other Jovian planets have masses many times greater than Earth.

• Surface Gravity and Density

  • Surface gravity much greater for Jupiter, Saturn, Uranus, and Neptune compared to Earth.

  • All have lower average densities (~1000 kg/m³), with Saturn being less dense than water, theoretically capable of floating.

Composition and Structure

• Predominantly composed of hydrogen and helium.

• Low-density nature due to massive gravitational force retaining atmospheric gases:

  • Unlike terrestrial planets that lost their original atmospheres, Jovian planets maintained them through stronger gravity.

• Core Structure

  • Possibly a rocky or icy core beneath atmospheric layers.

• Electromagnetic Fields

  • Generated by the rotation of the mantle.

  • Emit radio waves, contributing to their electromagnetic signature.

Rotation Characteristics

• Rotation varies by planet, with different inclinations:

  • Jupiter: nearly straight up and down.

  • Saturn: tilted at about 26-27 degrees.

  • Uranus: tipped on its side (97 degrees).

  • Neptune: tilted at about 30 degrees.

• Differential Rotation

  • Parts of the planet rotate at different speeds:

    • Jupiter's high latitudes take longer (six minutes) compared to the equator.

    • Saturn has a 25-minute difference.

    • Uranus has a two-hour difference; Neptune has a six-hour difference.

Interior Structure of Jovian Planets

• No solid surface; core and mantle models based on physical and chemical data:

  • Core potentially rocky or icy, specially in Uranus and Neptune.

  • Mantle primarily consists of compressed hydrogen:

    • Exhibits a slushy or metallic characteristic, indicating high pressure.

  • Atmosphere constitutes the outer layer, with no defined crust.

Future Exploration and Observations

• The next mission aims to delve deeper into understanding Jovian planets through animated models.

• Focus on comparative sizes, internal structures, and the excess heat radiation emitted by Jupiter and Saturn, suggesting significant internal energy.