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Outline Ch.6: Solar System
I.
Overall Properties of Solar System:
1.
2.
3.
4.



Nearly co-planar orbits (disk-shaped)
All planets orbit Sun in same direction as Sun’s
rotation
MOST (but not all) planets rotate in same
direction as their obits around Sun
Planets:
Small dense terrestrial planets in inner SS
Large, low density, Jovian planets in outer SS
Pluto is exception
(Cont.)
Outline Ch.6 (Cont.)
I.
Overall Properties (cont):
5.
6.
7.
II.
•
In general: closer to Sun, larger density
Hot near Sun, cold far away
Composition of Solar Nebula
Extrasolar Planets
Are there planets around other stars?
YES (more than 450 so far)
I. Overall Properties (cont):
7. Composition of Solar Nebula:
98% Hydrogen & Helium, 2% other elements
Condensation of solids from nebula:
 Inner part is hot, only high density materials
(metals and silicates) can condense
 Outer regions cooler, can condense lower density
materials like water ice and other ices
Near Sun: terrestrial planets
Far from: Sun Jovian planets
Condensation of Solids from Solar Nebula
Outline Ch.8 (Cont.)
II. Extrasolar Planets

More than 500 detected

Most detected indirectly using radial velocity
and transits in front of stars

Types of planets: most are strange (because
those are the ones we can detect). How are
they strange? Look it up
Outline of Earth (Ch. 7 part I )
I.
Earth as a planet (from Space)
II.
Atmosphere: composition, greenhouse
effect.
III. Surface Activity. Plate Tectonics
(continental drift and seafloor
spreading), volcanism, impacts, erosion
IV. Interior. Earthquakes, hot interior
(radioactivity) molten metallic core,
magnetic field.
Comparing the Terrestrial Planets
CO2, Water, Oxygen, Life
Carbon
Dioxide
Nitrogen
Oxygen
Venus
98%
Mars
95%
Earth
0.03%
1.9%
<<0.1
%
477ºC
2.7%
0.13%
78%
21%
-53ºC
13ºC
0.01
1.0
Surface
Temp
Atmospheri 90
c Pressure
(bars)
Water:
dry
dry surface
wet
A couple of questions…
 Where did the CO2 go?
• The Earth probably had 60-90 bars (60-90
times the current atmosphere) of CO2 in the
atmosphere….where is it?
• Dissolved by oceans and into sedimentary
rocks (we’re standing on it)
 When did the atmosphere become oxygenrich? Photosynthesis
Greenhouse Effect
 H2O, CO2, CH4 etc.
• Let UV and visible light through
• Trap infrared light
• Small changes in concentrations can cause
large climatic changes
Earthquakes and Volcanoes are mainly along
plate boundaries: Earth’s crust in motion
How do we know about Earth’s
interior?
•We study Earthquakes:
•P-waves
•S waves (do not penetrate liquids)
•Molten metal core and semi-liquid mantle
•Currents in Earth’s molten core generate the
magnetic field
Interior heat drives the motion on
the surface of the Earth
Impact Processes
•Have occurred on Earth as much or more than on the
Moon
•Famous craters on Earth:
•Meteor Crater in Arizona (~20,000 years ago)
•Chicxulub in Yucatan (~65 million years ago) at
K/T boundary: caused disappearance of 2/3 of
species including dinosaurs.
•Most craters on Earth have been eroded by rain,
glaciers and wind
Summary of Earth

Overall properties

Atmosphere. 77% N, 21% O, all others 2%.
Greenhouse effect.

Interior. Earthquakes, hot interior
(radioactivity) molten metallic core, magnetic
field.

Surface Activity. Plate Tectonics (continental
drift and seafloor spreading), earthquakes,
volcanism, impacts (now and in past), erosion.
Chapter 7 Part II
The Other Terrestrial Planets
Comparing the Terrestrial Planets
Venus is still
geologically
active
The larger the
planet, the
longer it stays
geologically
active
Outline Ch. 7
Mercury, Venus, Mars, Moon
Overall Properties of these Planets
I. Mercury: innermost planet, no
atmosphere, surface characteristics, slow
rotation, very weak magnetic field
II. Venus: Earth’s twin, atmosphere,
surface, interior, rotation, magnetic field,
evolution
III. Mars: atmosphere, surface, interior,
rotation, magnetic field, evolution, two
moons (Phobos Deimos), life on Mars?
IV. Moon
I.
Mercury: innermost planet, terrestrial

No atmosphere

Surface: cratered, with scarps (cliffs)
indicating shrinkage of the planet (metal
core cooled and shrank)

Interior: large metal core (most of Mercury’s
radius is the metal core)

Rotation: very slow

Very weak magnetic field (why, in spite of
large metal core?)
Did Mercury shrink?
Steep long cliffs formed when the core
cooled, shrinking the planet by ~20 km.
Mercury is probably geologically dead.
II. Venus: Earth’s twin,






atmosphere 90x thicker than Earth’s and
mostly CO2, sulfuric acid clouds and rain
Surface: volcanic and relatively young
Interior: probably similar to Earth
Rotation: very slow and retrograde
Magnetic field: weak (why?)
Evolution: no water, lots of CO2 in
atmosph. greenhouse  very hot
Atmospheres of Earth and Venus
Radar images
of Earth and
Venus
No indication of
plate tectonics on
Venus
Planet Distanc
e
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Mass
Moons Density
(AU)
(Earth =
1)
(Water =1)
0.39
0.72
1.0
1.5
5.2
9.5
19.2
30.1
0.05
0.9
1.0
0.11
318
95
17
17
0
0
1
2
28
18
21
8
5.43
5.25
5.52
3.95
1.33
0.70
1.29
1.64
39.5
0.002
3
2.03
Mars:








Atmosphere 100x thinner than Earth’s and mostly CO2.
Some water ice in poles and below the surface, evidence
of liquid water and thicker atmosph. in past
Surface: volcanic and cratered, largest volcano in SS
(Olympus Mons), very large canyon (Valles Marineris)
evidence of liquid water in past (dry riverbeds and lakes)
Interior: probably solid and geologically inactive (smaller
planets cool faster). i.e., Olympus Mons is an exticnt
volcano
Rotation: almost same as Earth (once every 23 hrs)
Rotation axis, about the same tilt as Earth. Does Mars
have seasons?
Magnetic field: weak (why?)
Evolution: smaller size, lost most of its atmosph. lost
surface water. Smaller size, interior cooled faster, no
more geologic activity
Moons, Phobos and Deimos
Mars from
Spacecraft
Mars’ Moons: Phobos and Deimos
Captured asteroids
Chapter 8 Part I
Jupiter and Saturn
Outline Ch. 8 part I
I.
Overall Properties of these Planets
II. Jupiter : Composition, atmosphere, interior,
rotation, magnetic field, moons, ring, impact of
comet SL9 in 1994.
III. Saturn: Composition, atmosphere, interior,
rotation, magnetic field, moons, rings.
I.
Jupiter and Saturn (Ch. 8 part I)
Overall Properties of these Planets

Largest in SS

Thick atmospheres, mostly H and He,
with CH4 (methane), NH3 (ammonia) and
other molecules

Liquid hydrogen interiors

Lower density than terrestrial planets

Strong magnetic fields, rings and many
moons
Jupiter

Composition : H, He, CH4, NH3, etc.

Atmosphere: very active, belts, zones, red spot

Interior: liquid hydrogen and metallic hydrogen

Rotation: fast (9.8 hrs)

Magnetic field: strongest in SS

Moons: Four Galilean satellites (miniature SS)
plus many other moons

Ring: dark and faint

impact of comet SL9 in 1994.
Jupiter’s Atmosphere
See animation in book (Ch. 8 )
Interiors
Less mass less gravity less compression.
The physical states of the cores of the less massive
jovians are less extreme (probably no metallic
hydrogen inside of U and N).
Io’s
Volcanoes
Io is
heated by
the tides
with
Jupiter
Europa
May have
an ocean of
liquid water
under its
icy surface.
Life there?
Saturn
Composition : H, He, CH4, NH3, etc.
Atmosphere: less active than Jupiter, belts, zones
Interior: liquid hydrogen and metallic hydrogen
Lowest density (would float on water)
Rotation: fast (11 hrs)
Magnetic field: strong (but not as much as Jupiter)
Ring: largest and brightest in SS. Composed of
many icy particles
Moons: largest is Titan has a thick atmosphere,
plus many other moons
NASA’s Cassini Spacecraft currently studying
Saturn
Saturn’s Moons: Titan has an
atmosphere of nitrogen and
methane
Outline of Uranus, Neptune and Pluto
(Ch.8 part II)
I.
Uranus and Neptune: Discoveries,
atmospheres, interiors, rotation,
magnetic fields, moons, rings, Uranus’
axis tilt and seasons.
II.
Pluto and Charon: Orbit, composition,
moon, why so different from Jovian
planets?
III. Transneptunian Bodies (the Kuiper belt)
I. Uranus and Neptune
Composition : H, He, CH4, NH3, etc.
Atmospheres: less active, dark spot on Neptune
Interior: liquid hydrogen but no metallic
hydrogen
Rotation: fast (~17 hours for both)
Magnetic field: strong (but not know how it is
produced)
Moons: many moons, Neptune’s Triton is larger
than Pluto and retrograde (probably captured)
Rings: dark and faint
Planet Distanc
e
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Mass
Moons Density
(AU)
(Earth =
1)
(Water =1)
0.39
0.72
1.0
1.5
5.2
9.5
19.2
30.1
0.05
0.9
1.0
0.11
318
95
17
17
0
0
1
2
28
18
21
8
5.43
5.25
5.52
3.95
1.33
0.70
1.29
1.64
39.5
0.002
3
2.03
Triton: largest of
Neptune’s moons
Larger
than Pluto
and in a
retrograde
orbit
Outline of Uranus, Neptune and Pluto
II.
Pluto and Charon: Orbit, composition,
moon, why so different from Jovian
planets?
Pluto and its three Moons
Outline of Uranus, Neptune and Pluto
(Ch. 8 part II)
III. Transneptunian Bodies (the Kuiper
belt):
 Many objects smaller than planets:
similar to the asteroid belt
 Largest object is slightly larger than
Pluto
 Source of some of the comets
 Triton may have formed in the Kuiper
belt was captured by Neptune
COMETS AND THEIR
COMPOSITION
(Ch. 9 part I)
OUTLINE
I. Nature of Comets
II. Comets and the Origin of Earth’s Water
III. Dust Composition
. Comet
Ikeya-Zhang March 2002.
Nature of Comets (Cont.)
 Two Known Sources of Comets
• Oort Cloud (spherical shell ~ 50,000-100,000 AU)
• Kuiper Belt (disk ~ 30-50 AU)
(Astronomical Unit [AU] = Earth-Sun Distance)
Oort Cloud
Sun
•
~105 AU
About 1/3
distance to
nearest star
Kuiper Belt
~50 AU
•
Sun
Neptune’s Orbit
Impact of Comet SL9 with Jupiter in 1994
IV. Comets and Origin of Earth’s Water
 Why is Earth rich in water and where did
this water come from?
 Comet impacts?
 Asteroid impacts?
 Probably both: The composition Earth’s
water is consistent with a cometary origin of
at least some of it. In addition, some
asteroids can have as much as 15% water
VI. SUMMARY OF COMETS
 Comets are composed mainly of H2O ice plus
cosmic dust and other ices
 The main features of a comet are the nucleus,
coma and tails
 There are two known sources of comets: Oort
Cloud and Kuiper Belt
 The chemical composition of comets (rich in
deuterium) is consistent with a cometary origin
of at least some of Earth’s water and organic
molecules
Asteroids and Meteorites
Ch9 part II
Asteroids and Meteorites Outline
I.
II.
Introduction
Asteroids
•
Orbits, sizes, composition
III. Meteorites
•
•
•
Irons
Stony-Irons
Stones
IV. Origin of Meteorites
V. Meteorites and the Solar System
VI. Summary
I. INTRODUCCION
 Asteroids, comets and meteorites are the
smallest members of the solar system
 All these objects tell us much about how the
rest of the solar sytem formed
II. ASTEROIDS
 Most have orbits between between Mars and
Jupiter
 Some have orbits that cross Earth’s, these are
known as Earth-crossing asteroids
 They have collided with Earth and they are
likely to do so again.
 The largest asteroid is Ceres
III. Types of Meteorites
 Irons
 Stony-Irons
 Stones (~75% of all meteorites)
III. Types of Meteorites
 Irons are excavated by collisions
 Stony-Irons are excavated by collisions
Iron
Iron and stone
Stone
Diferentiated Asteroid
Non-diferentiated Asteroid
III. Origin of Meteorites
 Asteroids (more than 95%)
• Asteroids collide with each other and breakup,
some of those fragments become meteorites
 Mars (a few percent)
• Impacts on Mars kick martian material into
space and some ends up falling on Earth
 Moon (a few percent)
• Also because of impacts
IV. Meteorites and the Solar System
 Age of Solar System (4.6x109 years)
determined from radioactive dating of
meteorites
 Meteorites and Planets:
• Information about asteroids, Mars,
Moon.
• Information about interior of Earth, e.g.,
iron core.
V. Summary of Asteroids and Meteorites
 Most asteroids orbit the Sun between Mars and
Jupiter
 Some asteroids cross Earth’s orbit and eventually
collide with Earth
 Ceres is the largest asteroid
 There are several types of asteroids
 Meteorites are solid objects from space that reach the
Earth’s surface
 Most meteorites are from asteroids, a few are from
Mars and the Moon. Most meteors are from comets
 Three types of meteorites: Irons, Stony-irons, Stones
 Meteorites tell us about the rest of the solar system.