The Solar System: Objectives
Importance of comparative planetology
Overall scale and structure of the solar system
Basic differences between terrestrial and jovian planets
Major nonplanetary components of the solar system
Why spacecraft missions are vital to our understanding of the solar system
Planet Properties
Distance from Sun
Orbital period
Radius
Mass
Rotation period
Average density
How do we measure Planet Properties?
Distance from Sun - Kepler's Law
Orbital period - Observed
Radius - angular size, small angle equation
Mass -Newton's law (need satellite)
Rotation period - observe surface or cloud features
Average density-r=(Greek letter rho)
r=Mass/Volume=M/V=4/3p R 3
Table of Planet Properties
Table 6.1
What is the density of Saturn?
Density = mass/volume
r =M/V
V=4/3 p R3
Layout of Solar System
Comparative Planetology
Comparative planetology is the study of planets by comparing and contrasting their properties in order to better understand how and why planets form evolve
A Solar System
A central massive star (or multiple stars)
Planets
Natural satellites (moons)
Planetary debris (asteroids, comets, dust, etc.)
Interplanetary medium
A Solar System
Spacing of Planets: Titius-Bode "Law"
Not a physical law, empirical (fit from data), no physical explanation for this
Jovian and Terrestrial Planets
Terrestrial Planets
Rocky in composition
Small
Dense
Close to Sun
Slow Rotation
Weak magnetic fields
Few Moons
No Rings
Inner planets: Mercury, Venus, Earth, Mars
Variety in Terrestrial Planets
All four have atmospheres: range from near vacuum (Mercury) to hot dense inferno (Venus)
Earth alone has Oxygen atmosphere, liquid water on surface
Different surfaces - heavily cratered to highly volcanic
Rotation Rate: Earth and Mars ~1 per day, Mercury and Venus months, Venus is retrograde rotation
Earth and Mars have moons, Mercury and Venus others none
Earth and Mercury have magnetic fields, Venus and Mars do not
Spacecraft Missions
Use Spacecraft to get closer look and measure:
Atmospheres (spectroscopy, samples)
Magnetic fields
Take samples (moon, Mars)
Measure composition (Venus, moon, Mars)
Image and Map surfaces
Detect moons, rings
Visit comets and asteroids
Gravitational Boosting
Cassini Mission to Saturn