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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. Chapter Outline. The Formation of the Solar System Exploring the Solar System The Earth.
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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.
Chapter Outline • The Formation of the Solar System • Exploring the Solar System • The Earth
Clues to the Origin of the Solar System • Solar system • Objects gravitationally bound to Sun • Deduction of origin • Observations • Earth • Space
Clue #1: Planetary Orbits • Features of solar system • All planets orbit in same direction • Orbits in same plane • Most rotate in direction of orbit
Clue #2: Distribution of Mass • Most material within Sun • Two types of planets • Terrestrial planets • Jovian planets • Other objects • Moons, asteroids, comets
The Nebular Hypothesis • Nebular Hypothesis • Cloud of dust and gas • 99% H and He • Collapse of nebula • Planetary orbits • Clumping of matter • Planetesimals • Temperature
Basic Planet Categories • Terrestrial planets • Mercury • Venus • Earth • Mars • Jovian planets • Jupiter • Saturn • Uranus • Neptune
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
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
Nebular Condensation Physics • Energy absorbed per unit area from Sun = energy emitted as thermal radiator • Solar Flux = Lum (Sun) / 4 x distance2 • Flux emitted = constant x T4 [Stefan-Boltzmann] • Concluding from above yields T = constant / distance0.5
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
The Formation of Earth • Planetesimals • Combined (accretion) to form earth • Great bombardment • Meteors • Growth of planet • 20 metric tons per day
Differentiation • Differentiation • Heat from collisions • Dense material sank to center • Lighter material rose to surface • Structure • Core • Mantle • Crust
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
Planetary Idiosyncracies • Cratering • Mercury, Mars, Moon • Few on Earth • weathering • Rotation • Venus • Earth’s axis • Uranus
The Evolution of Planetary Atmospheres • Earth’s atmosphere • Early • Outgassing • Atmosphere was N2, CO2, H2, & H2O • Gravitational escape • Living organisms
The Inner Solar System • Mercury, Venus, Mars • Mercury and Venus too hot for life • Mars Exploration • Multiple missions • Found evidence of water
The Outer Solar System • Jupiter, Saturn, Uranus, Neptune • Layered structure • No solid surface • Jupiter • Comet Shoemaker-Levy • Galileo spacecraft • Saturn • Cassini spacecraft
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 Moons and Rings
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)
Pluto’s Interior to SurfaceOld -> 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
The Launch of New Horizons Pluto Mission 17 Jan 2006 http://www.youtube.com/watch?v=KNJNaIoa5Hk