1. The Solar System

2. Brief version of formation
Frost line:
all gaseous stuff is blown away by the sun leaving the terrestrial planets
Jovian planets are beyond the frost line, so the gasses were protected

3. Terrestrial Planets

4. Earth Average distance from the Sun: 1.00 AU Radius: 6,378 km
Mass: 5.97 × 1024 kg
Avg. density: 5.52 g/cm3
Composition: rocks, metals
Average surface temperature: 290 K
Satellites: 1

5. Earth’s Structure Core – highest-density material, mostly Ni & Fe
Mantle – moderate density, mostly Si, O, etc.
Crust – lowest-density rock, granite & basalt
Lithosphere – rigid outer layer of a planet, including crust and upper part of mantle
Core can be divided into inner and outer core, where inner core is solid metal and the outer core is molten

6. Structure

7. Internal Heat Formation Geological Activity
Caused by accretion and collisions during formation
Also due to radioactive material
Differentiation
Convection and Cooling
Differentiation means that denser material falls toward the center while less dense material rises to the surface
Nearly all of the planet is actually solid. Only liquid part is just under the rigid lithosphere
Convection must occur under the lithosphere and is responsible for geological activity
Convection and the surface area / volume ratio are responsible for cooling
As the planet cools, the lithosphere becomes thicker, making less room for convection, slowly choking off geological activity

8. Magnetic Field
Caused by the motion of charged particles in Earth’s molten outer core
Magnetosphere protects us from solar wind
Aurora is caused when some particles do make it through the magnetosphere and collide with particles in the atmosphere
The magnetic field is not as thick at the poles, so that is where this most often occurs

9. Shaping Earth’s Surface
Cratering
Volcanism
Tectonics
Erosion
Meteor crater in Arizona. It is more that 1km across and 200m deep
Volcanism: volcano in Alaska
really important for Earth’s formation because without them we wouldn’t have an atmosphere
Outgassing – when gas is released into the atmosphere from under Earth’s crust
mostly CO2 released as well as H2O and H2S/SO2
outgassed water vapor rained down and formed the oceans and atmosphere
tectonics – surface compressing makes mountains
surface streching can make seas
sheer can cause earthquakes
result of mantle convection
Presence of Plates (plate tectonics) may be unique to Earth
Erosion piled stuff into layers, forming sedimentary rocks

10. Earth’s Atmosphere 77% N2, 21% O2 Protection
X-rays are absorbed high up in the atmosphere
Ozone absorbs UV
Visible light gets through no problem

11. Earth’s Atmosphere Scattering
Blue light is scattered more easily than red light
Sky is blue because sunlight gets scattered to your eye from all directions
Sun look red at sunrise/set because blue light gets scattered away
Rayleigh scattering I~(lambda)^-4

12. Greenhouse Effect 5800 K H2O CO2 CH4 Visible Light IR Light 300 K
Greenhouse gasses are gasses that are particularly good at absorbing IR radiation
H2O, CO2, CH4
Remind of Wien’s Law
IR Light
300 K
Ground

13. Geologically Dead Objects

14. The Moon Average distance from the Earth: 384,000 km Radius: 1,700 km
Mass: 7.3 × 1022 kg
Avg. density: 3.35 g/cm3
Period: 29.5 days

15. Geological Features Lunar Maria Micrometeorites
Lunar Maria are formed when a large impact struck the moon, fracturing the lithosphere. The mantle was heated up enough to melt by radioactivity. Molten lava flooded the crater. It is darker because of the Iron-rich composition of the mantle, which leaked through the lithosphere and flooded the crater.
Micrometeorites constantly strike the Moon’s surface because there is no atmosphere. These objects pulverize the surface material, creating a very fine dusty layer on the Moon’s surface.

16. Mercury Average distance from the Sun: 0.39 AU Radius: 2,440 km
= 0.38REarth
Mass: MEarth
Avg. density: 5.43 g/cm3
Composition: rocks, metals
Average surface temperature: 700 K day, 100 K night
Satellites: 0
88 day orbit, 59 day rotation

17. Geological Features One giant crater called “Caloris Basin”
Mercury is not that exciting.
One giant crater called caloris basin
Huge cliffs
One giant crater called “Caloris Basin”

18. Mars Average distance from the Sun: 1.52 AU Radius: 3,397 km
= 0.53REarth
Mass: 0.11 MEarth
Avg. density: 3.93 g/cm3
Composition: rocks, metals
Average surface temperature: 225 K
Satellites: 2

20. Perhaps it was more similar long ago
Mars vs. Earth
Similarities
Differences
Day is about 25 hours long
Polar caps
Axis tilted about the same
More extreme seasons in southern hemisphere
Polar caps contain CO2
Only about 1% of Earth’s atmosphere, which is CO2
Much colder
Perhaps it was more similar long ago

21. Martian Geology

22. Martian Geology Polar ice caps Higher elevation of southern hemisphere
Lack of craters in northern hemisphere
Tharsis Bulge, Valles Marineris
The Tharsis Bulge is a large elevated region home to some of the largest volcanoes in the solar system. Some believe it is actually one large volcanic system
The Valles Marineris was discovered by the Mariner spacecraft (hence the name) and is a huge tectonic crack, probably associated with the Tharsis Bulge

23. Martian Geology Olympus Mons The largest volcano in the solar system
Base covers an area equal to Arizona
26 km above average surface level, 3x the size of Mt. Everest

24. Water on Mars
Today the surface temperature and pressure to too low for liquid water
Polar caps
Ground water
Evidence of ancient H2O
Dried Riverbeds
Maybe not
Signs of erosion
“riverbeds” might actually have been formed by a surface collapse. Perhaps there is a lava tunnel or other flow under the surface that caved in.

25. What happened?
Mars cooled, and the core solidified, preventing the convection necessary to maintain a magnetic field

26. Venus Average distance from the Sun: 0.72 AU Radius: 6,51 km
= 0.95REarth
Mass: 0.82 MEarth
Avg. density: 5.24 g/cm3
Composition: rocks, metals
Average surface temperature: 740 K
Satellites: 0

27. Venusian Geology
Craters, volcanoes, tectonics somewhat similar to Earth
Coronae – bulges made by hot, rising plumes of mantle
No plate tectonics

28. Venusian Atmosphere Atmosphere about 90x as thick as Earths
Made up of about 96% carbon dioxide, but virtually no water
Why should the atmosphere be different from Earth’s?

29. Why are the atmosphere’s different?
Earth
Venus
Water rained into oceans
CO2 dissolved into water and then formed into carbonate rocks
Including the rocks, Earth has about as much carbon dioxide as Venus
Lacking water
Explains why there is more carbon dioxide in the atmosphere: cannot dissolve and become rock
Where did the water go?
UV light breaks up molecule

30. Runaway Greenhouse Effect

31. Life
What is necessary?

32. A few examples Liquid Water Atmospheric Oxygen Climate Stability
Planetary Size
Must be large enough so it doesn’t cool too quickly, preventing tectonics
Distance from Sun
Liquid Water

33. The CO2 Cycle CO2 dissolves in rainwater
This slightly acidic rain erodes rock and carries minerals to ocean
Carbonate rock is formed, which sinks to the bottom of the ocean
These rocks subduct and melt, releasing CO2
Volcanoes outgas CO2
The hotter it is, the more CO2 is pulled out of the atmosphere.
If it gets hotter, the greenhouse effect is diminished, keeping things stable

34. Global Climate Change These are average temperatures
There would be a much greater effect at the poles, melting polar caps

35. Global Climate Change
CO2 in the atmosphere corresponds to the average temperature
We need to reduce the amount of CO2 we release into the atmosphere
Don’t want a runaway greenhouse effect