Lecture 17 Flashcards
What is a Gas Giants
Relatively large planets that have deep atmospheres and have NO solid surfaces; have rings of particles around them, and many icy/rocky satellites
What is Jupiter’s atmosphere made of
- 90% H2 and 10% He
- little amounts of water,methane and ammonia
- Clouds in jupiter are made of ammonia ice
Difference between Earth and Jupiter
- Earth is composed of dense silicates while Jupiter is made up mostly of hydrogen and helium
- Jupiters magnetic field is 20,000 times that of earth
- Jupiter has a quicker period of rotation (9.9 hours)
- Jupiter is also much colder than earth
Jupiter internal structure
- Atmosphere and Molecular Hydrogen Layer - beneath the atmosphere, there is a molecular hydrogen layer that extends to about 20,000 km.
- Metallic Hydrogen Layer
- Core - Jupiter has a volatile-rich core estimated to be 10-15 times the mass of Earth
Differences between Jupiter and Saturn
- Jupiters magnetic field is significantly stronger than Saturn (20,000 vs 0.4)
- They are composed of the same things in the atmosphere
- Jupiter is slightly warmer than Saturn
Saturns Atmosphere
- 96% H2, 3% He, small amounts of Methane & Ammonia Clouds
What is the reason for Jupiters strong magnetic field (important)
- Jupiter’s strong magnetic field is attributed to its Metallic Hydrogen layer, which extends from 30,000 to 40,000 km and acts as the source of the dynamo that generates the magnetic field
- Other gas giants have a much smaller metallic hydrogen layer or they have dif internal structures (richer in ice and silicates)
Saturns internal structure
- eddies and cyclones cause by heat released from the planets interior
1. Atmosphere consists of H2 and He
2. Molecular Hydrogen Layer: 30,000km thick composed of H2
3. Metallic Hydrogen Layer: contains metallic H+
4. Core: volatiles and silicates
Uranus compared to Jupiter
- Uranus has a more complex composition than jupiter
- Significantly weaker magnetic field than jupiter
- Almost double the period of rotation of jupiter (uranus 17.2hr)
Uranus – Atmosphere & internal structure
Composition:
– 83% H2, 15% He, 2% CH4
- Internal Structure:
- rich in ice and silicates
- Core of volatiles and silicate rock
Uranus compared to Neptune
- Both have a complex bulk composition
- Same things make up the atmosphere
- similar magnetic fields & temps
Neptune – Atmosphere & Internal Structure
Composition:
– 80% H2
– 18% He
– 1.5% CH4
- Internal Struc: Higher density
- Core of ice and silicate rock
How each planet gets their heat
- Jupiter, Saturn have a greater internal heat than what they get from the sun
- Uranus receives less heat from the Sun and its heat is not solar; it has more rocky components.
- Neptune, despite being further from the Sun, generates more heat than it receives from the Sun. This heat is not solar and Neptune has the most rocky components among these planets.
Origins of gas Giants: Core Accretion Model
- This model involves the accretion of rock-ice planetesimals to form a core that is 10 to 20 Earth masses, which takes about 1 million years (Ma).
- The next step is the accretion of a massive gaseous envelope, which takes between 1 to 10 Ma.
- The problem with this model is that the nebula was all gone by 10 Ma after the start of the solar system.
Origins of gas Giants: Disk Instability Model: (MORE LIKELY ONE)
- This model involves the clumping of gas and dust in the disk.
- There is a sudden gravitational collapse to form the planet, which takes only a few hundred or thousand years (within the first 1 Ma).
- This model solves the problem of the nebula disappearing too quickly and is considered the most likely model for the formation of gas giants like Jupiter and Saturn
