Exploration of Planetary Cores

Introduction

• Discussion of the centers of planets, specifically the cores.
• Cores can be solid, liquid, or a mixture of both.
• Size varies between 20% to 85% of a planet's radius.

Types of Cores

• Gas Giants: Have cores smaller than terrestrial planets, but some larger than Earth (e.g., Jupiter's core is 10-30 times heavier than Earth's).
• Terrestrial Planets: Earth, Venus, Mars, Mercury, and the Moon have iron cores and silicate shells.

Geological Evolution

• Inner structures evolved similarly due to tectonomagmatic processes.
• Earth's magnetic field exists since ~3.45 Ga, related to liquid iron from primordial core.
• Melting of Earth's primordial iron core marked significant planetary development.

Core Characteristics by Planet

1. Mercury

• Outer core: Liquid metal; Inner core: Solid and nearly the same size as Earth’s inner core.
• Core fills ~85% of Mercury's volume.
• Active interior due to molten core, generating a weak magnetic field (1% of Earth's).

2. Venus

• Similar size and density to Earth, likely has a metallic core.
• Core primarily composed of iron and nickel with possible sulfur.
• No intrinsic magnetic field detected.
• High surface temperatures but mantle temperatures likely similar to those on Earth.

3. Earth

• Core composed mainly of liquid iron, alloyed with nickel.
• The inner core consists of solid iron divided into two layers based on iron polarity.
• Core size: ~3600 km, accounts for ~1/3 of Earth's mass.
• Extreme temperatures (4000-7000K) and dynamics generate Earth's magnetic field.

4. Mars

• Core radius: ~1200 km.
• Core possibly rich in sulfur; mantle more iron-rich.
• Evidence suggests a core-generated magnetic field existed in the past, now likely inactive.
• Recent volcanic activity indicated through young volcanic rocks.

5. Jupiter

• Core structure remains unclear, modeled from observations of temperature, mass, and pressure.
• Central temperature: ~25,000 K, high-pressure conditions (60-100 million atmospheres).
• Composed primarily of hydrogen (70%) and helium (24%), likely metallic hydrogen at depth.
• Strongest magnetic field in the solar system generated in its core.

6. Saturn

• Low density indicates a hydrogen-rich composition.
• Core likely a mix of rock and ice (15-18 Earth masses).
• Magnetic field produced similarly to Earth's, influenced by deep electric currents.

7. Uranus

• Higher proportion of heavier elements than hydrogen and helium.
• Pressure at the center: ~5 Megabars.
• Models suggest mixed ice and gas with a small or non-existent rocky core.

8. Neptune

• Densest gas giant, with a significant portion of molten rock materials and melted ice.
• No distinct inner core; materials spread uniformly throughout the interior.

Conclusion

• Limited knowledge about the centers of Jovian planets, but ongoing research continues to uncover valuable information.
• Encouragement for audience engagement and subscription for further exploration of planetary science.