Study Guide 4
STUDY GUIDE
Final Exam
I. General Solar System Properties
A. Orbits coplanar
B. Prograde motions
1. Orbits
2. Rotation (except Venus)
3. Orbits of moons
C. Composition and distances
1. Jovian are solar composition far from Sun
2. Terrestrials are rocky near the Sun
D. All must be explained by any theory of formation
Planet Types
Terrestrial Jovian
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Size Small Large
Mass Small Large
Density Large Small
Composition Rocky Gaseous (solar)
Distance Near Sun Far from Sun
Rotation Slow Rapid
II. Planetary Observations
A. Mass
1. Follow trajectory of satellite (natural or artificial)
2. Perturbations in the orbits of nearby planets
B. Atmosphere
1. Twilight extension
2. UV spectroscopy
C. Radius
1. Measure angular diameter and distance
2. Stellar Occultations
3. Radar
D. Density - Mass/Volume
E. Rotational Period
1. Surface features
2. Radar
3. Slant of spectral lines
a. need a rapid rotation rate
4. Light variations
F. Albedo
1. Informations or measurements required
a. Sun-planet, Earth-planet distances
b. Brightness of planet
c. Brightness of Sun
2. Provides basic information on surface conditions
a. affected by clouds, ice caps, atmospheres, oceans
G. Temperature
1. Radio Observations
III. Temperature variations
A. Seasons
1. Inclination of rotational pole
2. Eccentricity of orbit
B. Diurnal
1. Rotational rate
2. Atmosphere
a. cloud cover
b. Greenhouse Effect
3. Oceans
4. Albedo
IV. Magnetic fields
A. Need fluid core and rapid rotation
V. General solar system history
A. Formation 4.6 billion years ago
B. Major meteoric bombardment - 4.2 - 3.9 billion years ago
1. Caloris basin on Mercury
2. Maria on Moon
C. Smaller impacts since 3.9 billion years ago
1. Causes normal cratering
VI. Volcanism - need hot planetary interior
A. Radioactive decay
1. Enough to melt surface of moon and flood Maria 3.8
billion years ago
B. Tidal heating
1. Keeps Io hot
2. Warms Europa
C. Original heat and radioactive heating will radiate away to space
1. Smaller planets already have cold interiors
a. Mars, Moon, Mercury
D. Sites of volcanism
1. Earth - enough mass to keep interior warm
2. Mars - extinct (Olympus Mons)
3. Io - tidal heating
4. Possible on Venus
VII. Atmospheres
A. Primary (H. He, trace molecules like ammonia and methane)
1. Jovian planets
2. All planets began with primary atmospheres
B. Secondary
1. Carbon Dioxide
a. Mars - most escaped
b. Venus - very dense - strong Greenhouse Effect
2. Nitrogen
a. Earth - caused by volcanos
b. Titan
C. Planet's ability to hold an atmosphere depends on
1. Mass (gravity)
a. can compute lightest element retained
2. Temperature
a. distance from Sun, rotational rate
VIII.Stellar Occultations
A. If we know velocity of planet and time how long the star
disappears, we can compute size of the planet
B. Used to help determine or discover
1. Rings of Uranus
2. Diameter of Pluto
IX. Perturbations
A. Small deviations from expected orbit
B. Perturbations of the orbit of Uranus
1. Used to help find Neptune
2. Pluto is not responsible for remaining perturbations
- Planet X?
X. Specifics
A. Mercury
1. Similar to our Moon
2. Once rotated more quickly
a. wrinkled crust
b. residual magnetic field
3. High density
B. Venus
1. Retrograde rotation
2. Greenhouse Effect
a. liquid water never formed to dissolve carbon dioxide
as on Earth
C. Earth
1. Strong erosion
a. water, atmosphere
2. Protective shields
a. magnetic fields - protects us from charged particles
b. atmosphere - protects us from meteors and short
wavelength light (ozone layer)
D. Mars
1. Major terrains
a. volcanic
b. cratered
c. sinuous channels
d. sand dunes
2. Once had habitable climate
a. atmosphere dense enough to have liquid water
b. probably caused by volcanos
E. Jupiter
1. Similarities to Sun
a. emits more energy than it receives
b. differential rotation
c. composition
2. Strong magnetic field
a. radio emissions controlled by Io
F. Saturn
1. Ring system
a. gravitational resonances cause gaps
b. inside Roche lobe
c. either a shattered moon or material that couldn't
form into a moon
2. Moons made mostly of water ice
3. Titan
a. thick N2 atmosphere
G. Uranus
1. Very thin rings
2. Inclination of 98°
3. Miranda shows evidence of having been fragmented and reformed
H. Neptune
1. Very similar in size and mass to Uranus
2. Similar spots to Jupiter
3. Moons in erratic orbits
I. Pluto
1. Stellar occultations of 1968 and 1976
a. show Pluto to be very small
2. High albedo surface (possibly methane ice)
3. Double planet
a. Charon and Pluto similar in size
XI. Comets
A. Tails always point away from the Sun due to
1. Radiation pressure
2. Solar wind
B. Original solar system material
1. Comets originate in the Oort Cloud
XII. Meteors
A. Sporadic
1. Larger objects causing cratering on planets
2. Most come from asteroid belt
B. Showers
1. Debris left in the path of a comet