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I. Overall Properties of Solar System:1. Nearly co-planar orbits (disk-shaped)2. All planets orbit Sun in same direction as
Sun’s rotation3. MOST (but not all) planets rotate in same
direction as their obits around Sun4. Planets: Small dense terrestrial planets in inner SS Large, low density, Jovian planets in outer
SS Pluto is exception
(Cont.)
Outline Ch.6: Solar System
I. Overall Properties (cont):5. In general: closer to Sun, larger density6. Hot near Sun, cold far away7. Composition of Solar Nebula
II. Extrasolar Planets• Are there planets around other stars?
YES (more than 450 so far)
Outline Ch.6 (Cont.)
7. Composition of Solar Nebula:98% Hydrogen & Helium, 2% other elementsCondensation 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 planetsFar from: Sun Jovian planets
I. Overall Properties (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 Ch.8 (Cont.)
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.
Outline of Earth (Ch. 7 part I )
CO2, Water, Oxygen, LifeVenus Mars Earth
Carbon Dioxide
98% 95% 0.03%
Nitrogen 1.9% 2.7% 78%
Oxygen <<0.1%
0.13% 21%
Surface Temp
477ºC -53ºC 13ºC
Atmospheric Pressure (bars)
90 0.01 1.0
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 oxygen-rich? 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
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
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
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.
Summary of Earth
Comparing the Terrestrial Planets
Venus is still geologically
active
The larger the planet, the
longer it stays geologically
active
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
Outline Ch. 7Mercury, Venus, Mars, 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
Planet Distance
(AU)
Mass(Earth =
1)
Moons Density(Water
=1)
Mercury 0.39 0.05 0 5.43
Venus 0.72 0.9 0 5.25
Earth 1.0 1.0 1 5.52
Mars 1.5 0.11 2 3.95
Jupiter 5.2 318 28 1.33
Saturn 9.5 95 18 0.70
Uranus 19.2 17 21 1.29
Neptune 30.1 17 8 1.64Pluto 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
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.
Outline Ch. 8 part I
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 and Saturn (Ch. 8 part I)
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
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).
Interiors
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
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)
Outline of Uranus, Neptune and Pluto (Ch.8 part II)
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
I. Uranus and Neptune
Planet Distance
(AU)
Mass(Earth =
1)
Moons Density(Water
=1)
Mercury 0.39 0.05 0 5.43
Venus 0.72 0.9 0 5.25
Earth 1.0 1.0 1 5.52
Mars 1.5 0.11 2 3.95
Jupiter 5.2 318 28 1.33
Saturn 9.5 95 18 0.70
Uranus 19.2 17 21 1.29
Neptune 30.1 17 8 1.64Pluto 39.5 0.002 3 2.03
II. Pluto and Charon: Orbit, composition, moon, why so different from Jovian planets?
Outline of Uranus, Neptune and Pluto
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
Outline of Uranus, Neptune and Pluto (Ch. 8 part II)
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)
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
IV. Comets and Origin of Earth’s 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 OutlineI. Introduction
II. Asteroids• Orbits, sizes, composition
III. Meteorites• Irons• Stony-Irons• Stones
IV. Origin of Meteorites
V. Meteorites and the Solar System
VI. Summary
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
I. INTRODUCCION
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
II. ASTEROIDS
Irons are excavated by collisions
Stony-Irons are excavated by collisions
III. Types of Meteorites
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.