Download Week 7 Revision Lecture

Revision Lecture
Monday 14, 2009
Tides
• Ocean tides on Earth
– The effect of Sun and Moon
• Tides on the Moon
• Tides on Io
• Tides on Mercury
Magnetic fields
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Generation
Aurorae (Earth, Jupiter, Saturn)
Induced magnetic field
Magnetic field of the Sun and the solar
cycle.
The age of the Solar System
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4.56 billion years
4.56 x 109 years
4.56 giga years (Gyr)
4560 million years
Billion = 109 = giga
Difference between American and
British use of “billion”
Chemical Symbols
• Methane CH4
• Ammonia NH3
• Oxygen and nitrogen molecules O2 and
N2
• Carbon dioxide CO2
• Carbon monoxide CO
• Sufur dioxide SO2
• Sulfuric acid H2SO4
Their planets of choice:
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CH4 – J. S. U. N.
NH3 – J. S.
O2 and N2 - Earth
CO2 – Venus, Mars
CO
SO2 - Venus
H2SO4 - Venus
Temperatures
• Celcius vs. Kelvin: Remember 0o C = 273 K
or 0 K = -273o C
• What solar system body has a surface T of
40 K?
• What is the surface temperature of
Venus? Does it vary from night to day?
• What is the surface temperature of
Mercury? Does it vary from night to day?
Why the difference between Mercury and
Venus?
Resonances
• The dynamics of a system with more
than 2 bodies is complex and generates
resonances.
• The system tries to achieve the lowest
energy = highest stability.
• As everything orbits, some resonances
are stable (Pluto-Neptune; Io, Europa
and Ganymede). Others are not stable
(cleared gaps in Saturn’s rings).
Planetary densities
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Determination: Mass/Volume
Volume = 4/3 p R3
Mean density of Earth = 5515 kg/m3
Density of rock ≈ 3000 kg/m3
Density of water = 1000 kg/m3 = 1 gr/cm3
What do you deduce of a planet has
mean density << 3000 kg/m3?
Impacts and impact craters
• What was the era of heavy
bombardment?
• Where are craters seen?
• What do many craters mean?
• What planets/areas of planets/moons
have many craters? What have few?
The Greenhouse effect
• On Earth
• On Venus
• On Mars
Tectonic activity
Earth: plate tectonic
Venus: “flake” tectonic
Mars: Valles Marineris.
Importance of crust thickness on type
of tectonic activity.
• Ganymede: fractures on both light and
dark lands – tectonic activity.
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Internal heat
• Evidence:
– Recent tectonic activity seen on surface
– Own magnetic field
• Likelyhood:
– larger bodies retain heat more readily – they cool more
slowly – terrestrial planets activity as a function of
mass.
– Bodies which are tidally stressed can be kept warm
(Io).
• Strange examples:
– Ganymede
– Titan (reheating?)
– Enceladus (tidal?)
Liquid, solid or gas?
Space Missions
Mercury: Mariner 10, Messenger
Venus: Venera, Magellan
Mars: Vikings 1-4, Pathfinder, Rovers …
Jupiter: Pioneers 10,11, Voyagers 1,2,
Galileo
• Saturn: Voyagers 1,2, Cassini
• Uranus + Neptune: Voyagers 1,2
• Pluto: New Horizons
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