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 Generation Aurorae (Earth, Jupiter, Saturn) Induced magnetic field Magnetic field of the Sun and the solar cycle.

The age of the Solar System 4.56 billion years 4.56 x 10 9 years 4.56 giga years (Gyr) 4560 million years Billion = 10 9 = giga Difference between American and British use of “billion”

Chemical Symbols Methane CH 4 Ammonia NH 3 Oxygen and nitrogen molecules O 2 and N 2 Carbon dioxide CO 2 Carbon monoxide CO Sufur dioxide SO 2 Sulfuric acid H 2 SO 4

Their planets of choice: CH 4 – J. S. U. N. NH 3 – J. S. O 2 and N 2 - Earth CO 2 – Venus, Mars CO SO 2 - Venus H 2 SO 4 - 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 Determination: Mass/Volume Volume = 4/3  R 3 Mean density of Earth = 5515 kg/m 3 Density of rock ≈ 3000 kg/m 3 Density of water = 1000 kg/m 3 = 1 gr/cm 3 What do you deduce of a planet has mean density << 3000 kg/m 3 ?

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.

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