the solar system. terrestrial planets earth average distance from the sun: 1.00 au radius: 6,378 km...
TRANSCRIPT
The Solar System
Terrestrial Planets
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
Earth’s Structure
• Core – highest-density material, mostly Ni & Fe
• Mantle – moderate density, mostly Si, O, etc.
• Crust – lowest-density rock, granite & basalt
Structure
Internal Heat
Formation• Caused by accretion and
collisions during formation• Also due to radioactive
material
• Differentiation
Geological Activity• Convection and Cooling
Magnetic Field
• Caused by the motion of charged particles in Earth’s molten outer core
• Magnetosphere protects us from solar wind
Shaping Earth’s Surface
• Cratering
• Volcanism
• Tectonics
• Erosion
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
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
Greenhouse Effect
Ground
Visible Light IR L
ight
H2O CO2 CH4
300 K
kT
5800 K
Geologically Dead Objects
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
Geological Features
Lunar Maria Micrometeorites
Mercury• Average distance from the
Sun: 0.39 AU• Radius: 2,440 km
= 0.38REarth
• Mass: 0.055 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
Geological Features
One giant crater called “Caloris Basin”
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
Mars vs. Earth
Similarities• Day is about 25 hours long
• Polar caps
• Axis tilted about the same
Differences• 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
Martian Geology
Martian Geology
• Polar ice caps• Higher elevation of
southern hemisphere• Lack of craters in
northern hemisphere• Tharsis Bulge, Valles
Marineris
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
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
What happened?
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
Venusian Geology
• Craters, volcanoes, tectonics somewhat similar to Earth
• Coronae – bulges made by hot, rising plumes of mantle
• No plate tectonics
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?
Why are the atmosphere’s different?
Earth• 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
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
Runaway Greenhouse Effect
Life
What is necessary?
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
The CO2 Cycle
Global Climate Change
Global Climate Change