Download The Inner Solar System

The Inner Solar System
The Earth
Characteristics of Earth
A terrestrial, rocky planet
• Solid Fe-Ni inner core
• Molten outer core
• Mantle: silicates
• Crust (lithosphere): igneous rocks
Tectonically - active
• Radioactive decay and settling heats core
• Mantle convects heat to surface
• Crust floats on mantle
• Crust is created and destroyed
Characteristics of Earth
Today
Surface:
• 70% water
• 30% land
Atmosphere:
•77% N2
•21% O2
•0.1% H2O
•+Ar, CO2, Ne
The Dynamic Earth
Molten Core  planetary magnetic field
- this protects us from solar and galactic cosmic rays
Plate tectonics  refreshes atmosphere
Oceans  sequester CO2
Subduction  removes CO2 to mantle
The Terrestrial Atmosphere
The equilibrium temperature is 245K
The mean temperature is 287K due to the
greenhouse effect
The atmosphere (O2) is chemically unstable
and maintained by plants
The Moon
A Double Planet?
As seen from
Mars!
Luna
1/81 M
1/4 R
: 3.3 gm/cm3
No atmosphere
No tectonics
Tidally-locked
Receding from
Earth
Stabilizes Earth
Venus
Venus
Venus
A twin of the Earth?
•0.81 M
•0.95 R
• = 5.25 gm/cm3
Equilibrium temperature: 35C
Surface temperature: 470C
Surface pressure: 90 bars
CO2 atmosphere, H2SO4 clouds
No plate tectonics
A Habitable Venus?
No
Venus: What Went Wrong?
A runaway greenhouse:
H2O evaporates
CO2 can’t dissolve in oceans
internal heat dissipates (~R2/M)
tectonics ceases
Mars
Martian Characteristics
Small: mass = 0.1M
radius = 0.5 R
density = 4.0 gm/cm3
Cold: T ~ -50C
Thin atmosphere:
0.007 bars
95% CO2
An Earthlike Mars?
•Ice clouds
•Polar caps
•Evidence of running water
•Large volcanos
A Habitable Mars?
Maybe, before it lost its atmosphere
Nh
Planets in the Solar Habitable Zone:
Venus
Potentially Habitable (at some time):
Venus, Earth, Mars
In the extended habitable zone:
Europa, Titan
Nh = ???