Formation of Our Solar System

Northeastern Illinois University

Greg Anderson Department of Physics & Astronomy Northeastern Illinois University

Spring 2018

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 1 / 43 Northeastern Illinois University

Recap Our Solar System Patterns of Motion Patterns of Motion and Exceptions The solar system

Solar Nebula Age of the Solar System Recap Review

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 2 / 43 Northeastern Illinois Our Solar System University

Solar System c NASA Components • The Sun Patterns • Inner Terrestrial Planets • Patterns of Composition • Outer Jovian Planets • Patterns of Motion • Asteroids and Comets

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 3 / 43 Northeastern Illinois Patterns of Motion University

Animation

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 4 / 43 Northeastern Illinois Patterns of Motion and Exceptions University

Neptune

Earth

Saturn Mercury Venus Jupiter

Uranus Mars

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 5 / 43 Northeastern Illinois The solar system University

• Patterns of Composition: • Two major types of planets ☛ rock and metal ⇒ Terrestrial ☛ Ice and Gas ⇒ Jovian

• Swarms of smaller bodies ☛ rock and metal ⇒ Asteroids ☛ Ice ⇒ Comets

• Patterns of Motion: counter-clockwise viewed from NCP. • Exceptions: rotation of Venus and Uranus, Neptune’s retrograde moon Triton.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 6 / 43 Northeastern Illinois University

Recap

Solar Nebula Nebular Theory Formation of Protostar & Planetary Disk Orion Nebula Collapsed Solar Nebula Disks Disks The Solar Nebula Disks Gravitational Orbits Circular Orbits Animations Eddies in the Collapsing Nebula Composition Q: Nebula Composition Q: Solar Nebula Frost Line Planet Formation Accretion of Planets Moon Formation GIH Moon c 2012-2018G. Formation Anderson Universe: Past, Present & Future – slide 7 / 43 Late Heavy Northeastern Illinois Nebular Theory University

Nebular Theory: Kant 1755, Laplace 1795 Our solar system formed from a giant cloud (nebula) of interstellar gas and dust. Denser regions of the solar nebula experienced stronger gravity and begin gravitational contraction. Heating, Spinning, Flattening • The Rotational speed of cloud increased as it contracted due to conservation of angular momentum: • Collisions between particles in the collapsing nebula ﬂattened it into a ﬂat disk with circular orbits. • The nebula temperature increased as it collapsed due to conservation of energy As the protoplanetary disk cooled, metal, rock and ice condense, coagulate and accrete into planetesimals and then planets.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 8 / 43 Northeastern Illinois Formation of Protostar & Planetary Disk University Large, diﬀuse, slowly-rotating cloud collapses to a warmer, denser,

b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b more rapidly rotating disk and bulge. b b b b b b b b b b b b b b b b b bb b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b bb b b b b b b b b b b b b b b b b b b b b b b topb view b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b 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b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Conservation of Angular momentum:b b b bb b b b Cloudb b Spinsb b b b b fasterb as it collapses, L = mrv. Conservation of Energy: Cloud heats up as it collapses (gravitational potential → thermal) Flattening: Collisions between particles damp vertical motion.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 9 / 43 5 2000M⊙ star forming region. Destined to become an open cluster in 10 yrs.

M42: Orion Nebula, Image Credit: NASA/HST

Northeastern Illinois Disks Around β Pictoris University

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 12 / 43 HD 141569 Circumstellar Disk HL Tauri Protoplanetary disc Credit: ALMA (ESO/NAOJ/NRAO) Northeastern Illinois Gravitational Orbits University

Elliptical: Bound

Parabolic: Unbound Hyperbolic: Unbound

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 15 / 43 Northeastern Illinois Circular Orbits University

Collisions between gas particles in a cloud gradually reduce random motions and produce circular orbits.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 16 / 43 Northeastern Illinois Animations University

• Stellar Gas Cycle • Solar Nebula Collapse • Formation of Protoplanet Disk • Why does the disk ﬂatten? • Formation of nearly circular orbits • Nebular capture • The solar wind

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 17 / 43 Planets form as a natural byproduct of star formation. Northeastern Illinois Composition of the Solar Nebula University

TCondensation Abundance (by mass) H and He - 98% H Compounds < 150 K 1.4% Rock 500 − 1300 K 0.4% Metals 1000 − 1600 K 0.2%

H, He Hydrogen compounds include: 98% Rock & Metal: • water (H2O) 0.6% H compounds • ammonia (NH3) 1.4% • methane (CH4)

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 19 / 43 Northeastern Illinois Q: Nebula Composition University

Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?

A) Light gases (H, He), hydrogen compounds (H2O, CH4, NH3), rocks, metals

B) Hydrogen compounds (H2O, CH4, NH3), light gases (H, He), rocks, metals

C) Light gases (H, He), hydrogen compounds (H2O, CH4, NH3), metals, rocks

D) Hydrogen compounds (H2O, CH4, NH3), light gases (H, He), metals, rocks

E) Hydrogen compounds (H2O, CH4, NH3), rocks, metals, light gases (H, He)

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 20 / 43 Northeastern Illinois Q: Nebula Composition University

Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?

A) Light gases (H, He), hydrogen compounds (H2O, CH4, NH3), rocks, metals

B) Hydrogen compounds (H2O, CH4, NH3), light gases (H, He), rocks, metals

C) Light gases (H, He), hydrogen compounds (H2O, CH4, NH3), metals, rocks

D) Hydrogen compounds (H2O, CH4, NH3), light gases (H, He), metals, rocks

E) Hydrogen compounds (H2O, CH4, NH3), rocks, metals, light gases (H, He)

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 20 / 43 Northeastern Illinois Q: Solar Nebula University

What percentage of the solar nebula’s mass consisted of hydrogen and helium gases? A) 0.5 percent B) 5 percent C) 50 percent D) 98 percent E) 100 percent

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 21 / 43 Northeastern Illinois Q: Solar Nebula University

What percentage of the solar nebula’s mass consisted of hydrogen and helium gases? A) 0.5 percent B) 5 percent C) 50 percent D) 98 percent E) 100 percent

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 21 / 43 TFrost ≈ 150 K T >TF T = TF T

b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Frostb b Line b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b 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b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bbb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Rocky Planetesimals b b

Icy Planetesimals ⇒ Gas Giants Northeastern Illinois Planet Formation University

Terrestrial • Small particles of rock & metal were present inside the frost line. • Planetesimals of rock & metal built up as these particles collided. • Gravity eventually assembled these planetesimals into terrestrial planets. Jovian Planets • Ice could form small particles outside the frost line. • Large planetesimals of dirty ice were able to form. • The gravity of the larger planets allowed them to draw in H and He gasses.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 23 / 43 Northeastern Illinois Accretion of Planets University

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 24 / 43

Northeastern Illinois Giant Impact Hypothesis (GIH) University

4.4–4.45 Gya: Mars sized planet (Theia) and pre-Earth (90% of current size) collide. Cores merge and mantle material is ejected that would later form the Moon. Earth day after impact may have been 5 hours long. Hartmann & Davis (1975), Cameron & Ward (1976). Evidence • Lunar oxygen isotope ratios identical to those of Earth. • High denisty of Earth and low density of Moon. • Large angular momentum of Earth-Moon system. YouTube: moonorigin

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 26 / 43

Northeastern Illinois Late Heavy Bombardment University

Hypothesis: • Isotopic dating of Moon rocks brought back by Apollo indicate that the Moon was completely resurfaced by impacts around 4.1 – 3.8 billion years (Ga) ago: • All of the terrestrial planets would have been heavily impacted. • This period of impacts may have been produced by the migrations of gas giants.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 28 / 43 Northeastern Illinois Q: Nebular Theory University

The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?

A) Planets orbit around the Sun in nearly circular orbits in a ﬂattened disk.

B) the compositional diﬀerences between the terrestrial and Jovian planets

C) the equal number of terrestrial and Jovian planets

D) the presence of asteroids and comets

E) the craters on the Moon

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 29 / 43 Northeastern Illinois Q: Nebular Theory University

The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?

A) Planets orbit around the Sun in nearly circular orbits in a ﬂattened disk.

B) the compositional diﬀerences between the terrestrial and Jovian planets

C) the equal number of terrestrial and Jovian planets

D) the presence of asteroids and comets

E) the craters on the Moon

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 29 / 43

Northeastern Illinois Formation Summary University • Rock, metals, and ices condensed outside the frost line, but only rock and metals condensed inside the frost line. • Small solid particles collected into planetesimals that then accreted into planets. • Planets inside the frost line were made of rock and metals. • Additional ice particles outside the frost line made planets there more massive, and the gravity of these massive planets drew in H and He gases. • Solar wind blows away leftover gas

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 31 / 43 Northeastern Illinois Q: Solar Wind University

Observations of young stars (as well as theory) tell us that when the Sun was young, the solar wind A) was weaker than it is today. B) was stronger than it is today. C) was about the same strength as it is today. D) was nonexistent. E) blew outward only along the Sun’s poles.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 32 / 43 Northeastern Illinois Q: Solar Wind University

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 32 / 43 Northeastern Illinois Exceptions to the General Pattern University

Gravitational close encounters, impacts , captures lead to exceptions including: • Retrograde rotation of Venus • 98◦ axial tilt of Uranus • Triton’s retrograde orbit around Neptune • Earth’s relatively large moon

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 33 / 43 Northeastern Illinois University

Recap

Solar Nebula Age of the Solar System Age Meteorite Cross-sections Radioactive Decay Q: Radioactive Dating Zircon Dating Age of the Solar System Patterson’s Result Further Study

Review

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 34 / 43 Northeastern Illinois How old is the Solar System? University

Computer models: planetary formation lasted . 50 million years. Radiometric dating: • Oldest Moon Rocks 4.4 billion years ago. • Oldest meteorites 4.55 billion years old. • Oldest known mineral on Earth 4.4 billion year old, Australian zircon (ZrSiO4) enclosed in a metomorphosed sandstone conglomerate. The Solar System is about 4.5 billion years old

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 35 / 43 Northeastern Illinois Meteorite Cross-sections University

c SaharaMet/R. Pelisson

More meteorite photographs at: • http://www.saharamet.org • http://www.meteorlab.com

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 36 / 43 Northeastern 40 → 40 − Illinois Radioactive Decay K Ca + e +¯ν (89%) University 40K+ e− → 40Ar + ν (11%) 1 t1/2 =1.25 billion years

K Ca + Ar

1/2

Fraction of isotope 1/4

1/8 0 0 1 2 3 4 5 1.25 2.5 3.75 Time since rock formed (billions of years)

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 37 / 43 Northeastern Illinois Q: Radioactive Dating University

Suppose you ﬁnd a rock originally made of potassium-40, half of which decays into either argon-40 or calcium-40 every 1.25 billion years. You open the rock and ﬁnd 15 atoms of either calcium-40 or argon-40 for every 1 atom of potassium-40. How long ago did the rock form?

A) 1.25 billion years ago

B) 2.5 billion years ago

C) 3.75 billion years ago

D) 5 billion years ago t =0

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 38 / 43 Northeastern Illinois Q: Radioactive Dating University

A) 1.25 billion years ago

B) 2.5 billion years ago

C) 3.75 billion years ago

D) 5 billion years ago

t = t1/2 1.25 billion years

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 38 / 43 Northeastern Illinois Q: Radioactive Dating University

A) 1.25 billion years ago

B) 2.5 billion years ago

C) 3.75 billion years ago

D) 5 billion years ago

t =2t1/2 2.5 billion years

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 38 / 43 Northeastern Illinois Q: Radioactive Dating University

A) 1.25 billion years ago

B) 2.5 billion years ago

C) 3.75 billion years ago

D) 5 billion years ago

t =3t1/2 3.75 billion years

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 38 / 43 Northeastern Illinois Q: Radioactive Dating University

A) 1.25 billion years ago

B) 2.5 billion years ago

C) 3.75 billion years ago

D) 5 billion years ago

t =4t1/2 5.00 billion years

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 38 / 43 Northeastern Illinois Zircon Dating University

Zircon, (ZrSiO4), minerals incorporate trace amounts of uranium but reject lead.

Naturally occuring uranium: • U-238: 99.27% • U-235: 0.72% Decay chains: • 238U −→ 206Pb, τ =4.47 Gyrs. • 235U −→ 207Pb, τ = 704 Myrs. 1956, Clair Camron Patterson dated the Canyon Diablo meteorite: τ =4.55 Gyrs.

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 39 / 43 Northeastern Illinois Patterson’s Result University Geochimica et Cosmochimica Acta, 1956, Vol 10, pp. 230 to 237. Pergamon Press Ltd., London 40

Stony .6 Gyr 30 Meteorites t = 4 Pb .5 Gyr

204 = 4 20 t

b b Pb/

Chondrites 207

bb 10 Canyon Diabla (Iron) Meteorite

0 0 10 20 30 40 50 60 206Pb/204Pb

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 40 / 43 Northeastern Illinois Further Study University

• Lunar Origin: The Giant Impact.mov • Moon Origin • Formation of Moon • Origin of Moon (Nature) Next Terrestrial Planets

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 41 / 43 Northeastern Illinois University

Recap

Solar Nebula Age of the Solar System

Review Review Review

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 42 / 43 Northeastern Illinois Review University

• How old is the solar system? • What was the approximate composition of the solar nebula? • As the solar nebula contracted under gravity, what were the consequences of the conservation of energy and the conservation of angular momentum. • What is the frost line? Where was it located? • Where are the terrestrial and jovian planets located in relation to the frost line? • Why are Jovian planets bigger than terrestrial planets? • Why do we have asteroids and comets? • What is the Giant Impact Hypothesis?

c 2012-2018G. Anderson Universe: Past, Present & Future – slide 43 / 43