Overview
This lecture explains the composition and internal structure of Jovian (gas giant) planets, comparing them with terrestrial planets like Earth.
Jovian Planets: Composition and Structure
- Jovian planets are also called gas giants but the term can be misleading.
- They have a significant solid component: each has a rocky core made of rock and metal.
- The rocky core of Jupiter is larger than Earth, so Jupiter likely contains more solid material than Earth.
- Despite more total solid, Jovian planets are not called "mostly solid" because their mass is dominated by gas and liquid layers.
Why "Gas Giant" Is Used
- The large amount of gas and liquid overshadows the solid core, so classification is based on what is most abundant.
- Analogy: Despite having more “M&Ms” (solids), Jupiter is called "Skittles guy" (gas/liquid) because it is mostly other material.
Oceans on Earth vs Jupiter
- Earth's oceans are very thin compared to the planet's diameter.
- Jupiter’s "ocean" is thousands of times deeper than Earth’s, enough to submerge multiple Earths stacked atop each other.
Nature of Jupiter’s Ocean
- Jupiter’s deep ocean is NOT water; it is composed of liquid hydrogen and helium.
- These are the lightest and most common elements, and also the main components of the Sun.
Key Terms & Definitions
- Jovian planets — The outer planets (Jupiter, Saturn, Uranus, Neptune) characterized by large size and thick atmospheres.
- Gas giants — Another term for Jovian planets, emphasizing their gaseous envelopes.
- Rocky core — The dense, central part of a Jovian planet, made from rock and metal.
- Liquid hydrogen and helium — The substances making up the vast oceans inside gas giants.
Action Items / Next Steps
- Review the structure and composition differences between terrestrial and Jovian planets.
- Understand the reasoning behind planetary classification based on predominant materials.