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):

Condensation of Solids from Solar Nebula

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 )

Comparing the Terrestrial Planets

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

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

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

Chapter 7 Part IIThe Other Terrestrial Planets

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

Atmospheres of Earth and Venus

Radar images of Earth and

Venus

No indication of plate tectonics on

Venus

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

Mars from Spacecraft

Mars’ Moons: Phobos and Deimos

Captured asteroids

Chapter 8 Part I Jupiter and Saturn

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

Jupiter’s Atmosphere

See animation in book (Ch. 8 )

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

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?

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

Saturn’s Moons: Titan has an atmosphere of nitrogen and

methane

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

Triton: largest of Neptune’s moons

Larger than Pluto

and in a retrograde

orbit

II. Pluto and Charon: Orbit, composition, moon, why so different from Jovian planets?

Outline of Uranus, Neptune and Pluto

Pluto and its three Moons

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)

COMETS AND THEIR COMPOSITION

(Ch. 9 part I)

OUTLINEI. 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

• ~105 AUSun

About 1/3 distance to nearest star

Kuiper Belt

•

~50 AU

Sun

Neptune’s Orbit

Impact of Comet SL9 with Jupiter in 1994

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 MeteoritesCh9 part II

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

Stony-Irons

Stones (~75% of all meteorites)

III. Types of Meteorites

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.