1 Earth and Other Planets 3 November 2015 Chapter 16 Great Idea: Earth, one of the planets that orbit the Sun, formed 4.5 billion years ago from a great cloud of dust.

2 Chapter Outline The Formation of the Solar System Exploring the Solar System The Earth

3 The Formation of the Solar System

4 Clues to the Origin of the Solar System Solar system –Objects gravitationally bound to Sun Deduction of origin –Observations Earth Space

5 Clue #1: Planetary Orbits Features of solar system –All planets orbit in same direction –Orbits in same plane –Most rotate in direction of orbit

6 Clue #2: Distribution of Mass Most material within Sun Two types of planets –Terrestrial planets –Jovian planets Other objects –Moons, asteroids, comets

7 The Nebular Hypothesis Nebular Hypothesis –Cloud of dust and gas –99% H and He Collapse of nebula –Planetary orbits –Clumping of matter –Planetesimals –Temperature

8 Basic Planet Categories Terrestrial planets –Mercury –Venus –Earth –Mars Jovian planets –Jupiter –Saturn –Uranus –Neptune

9 Some Conclusions Planets formed at same time as Sun Planetary and satellite/ring systems are similar to remnants of dusty disks such as that seen about stars being born Planet composition dependent upon where it formed in solar system

10 Nebular Condensation (protoplanet) Model Most remnant heat from collapse retained near center After sun ignites, remaining dust reaches an equilibrium temperature Different densities of the planets are explained by condensation temperatures Nebular dust temperature increases to center of nebula

11 Nebular Condensation Physics Energy absorbed per unit area from Sun = energy emitted as thermal radiator Solar Flux = Lum (Sun) / 4 x distance 2 Flux emitted = constant x T 4 [Stefan-Boltzmann] Concluding from above yields T = constant / distance 0.5

12 Nebular Condensation Chemistry

13 Nebular Condensation Summary Solid Particles collide, stick together, sink toward center –Terrestrials -> rocky –Jovians -> rocky core + ices + light gases Coolest, most massive collect H and He More collisions -> heating and differentiating of interior Remnants flushed by solar wind Evolution of atmospheres

14 Pictorial View of Origins

15 Pictorial View Continued

16 HST Pictorial Evidence

17 HST Pictorial Evidence

18 The Formation of Earth Planetesimals –Combined (accretion) to form earth Great bombardment –Meteors –Growth of planet 20 metric tons per day

19 Differentiation –Heat from collisions –Dense material sank to center –Lighter material rose to surface Structure –Core –Mantle –Crust

20 Crust and Us

21 Earth’s Interior - How We Know It

22 The Formation of the Moon Large object (asteroid close to size of Mars) impacted earth Parts of mantle blown into orbit Moon formed from this material

23 Planetary Idiosyncracies Cratering –Mercury, Mars, Moon –Few on Earth weathering Rotation –Venus –Earth’s axis –Uranus

24 The Evolution of Planetary Atmospheres Earth’s atmosphere –Early –Outgassing Atmosphere was N 2, CO 2, H 2, & H 2 O –Gravitational escape –Living organisms

Exploring the Solar System

26 The Inner Solar System Mercury, Venus, Mars –Mercury and Venus too hot for life Mars Exploration –Multiple missions –Found evidence of water

27 The Outer Solar System Jupiter, Saturn, Uranus, Neptune –Layered structure –No solid surface Jupiter –Comet Shoemaker-Levy –Galileo spacecraft Saturn –Cassini spacecraft

Outer Solar System II 28

29 Moons and Rings Jupiter’s Moons –Io, Europa, Ganymede, Callisto and 63 others known Saturn’s Moons –Titan, Mimas, Hyperion and about 59 (61?) others Rings –Ice and rock - more ice in Saturn’s rings

30 Dwarf Planet Pluto Surprises It has moons Original moon discovered 1978 –Charon (KAIR’ en) Now more –2005 discovery of 2 additional moons –Named Nix and Hydra –2011 #4 is P4 (Kerberos) –July 7, 2012 #5 is P5 (Styx)

31 Pluto’s Interior to Surface Old -> New Model Model 1 –partially hydrated rock core –water ice layer II –predominant water ice layer I Model 2 –partially hydrated rock core –organics layer –predominantly water ice layer

32 The Launch of New Horizons Pluto Mission 17 Jan

33 Io’s Volcanoes from New Horizons

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Pluto 35

Pluto’s Methane (frozen) 36

Charon 37

Pluto 38

Pluto Atmosphere Detection 39

Pluto and Charon 40

Carbon Monoxide (Frozen) 41

Solar Wind at Pluto 42

Pluto “Heart” Region 43

Pluto Mountain Range 44

Nix and Hydra 45

Pluto, True Color 46

51 Asteroids, Comets, and Meteors Asteroids –Small rocky bodies –Orbit sun –Most in belt between Mars and Jupiter Comets –Dirty snowballs Orbit outside Pluto Oort cloud Kuiper belt –Halley’s Comet –Stardust and Deep Impact missions Meteoroids, Meteors, and Meteorites –Meteor showers –Original solar system material

52 Planetary Summary