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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. 1 Chapter Outline • The Formation of the Solar System • Exploring the Solar System • The Earth 2 The Formation of the Solar System 3 Clues to the Origin of the Solar System • Solar system – Objects gravitationally bound to Sun • Deduction of origin – Observations • Earth • Space 4 Clue #1: Planetary Orbits • Features of solar system – All planets orbit in same direction – Orbits in same plane – Most rotate in direction of orbit 5 Clue #2: Distribution of Mass • Most material within Sun • Two types of planets – Terrestrial planets – Jovian planets • Other objects – Moons, asteroids, comets 6 The Nebular Hypothesis • Nebular Hypothesis – Cloud of dust and gas – 99% H and He • Collapse of nebula – Planetary orbits – Clumping of matter – Planetesimals – Temperature 7 Basic Planet Categories • Terrestrial planets – – – – Mercury Venus Earth Mars • Jovian planets – – – – Jupiter Saturn Uranus Neptune 8 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 9 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 10 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 11 Nebular Condensation Chemistry Molecule H2 H2O CH4 NH3 FeSO4 SiO4 Freezing Point Distance from Center 10 K >100 AU 273 K >10 AU 35 K >35 AU 190 K >8 AU 700 K >1 AU 1000 K >0.5 AU 12 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 13 iClicker Question The most abundant chemical element in the solar nebula A Uranium B Iron C Hydrogen D Helium E Lithium 14 Pictorial View of Origins 15 Pictorial View Continued 16 HST Pictorial Evidence 17 HST Pictorial Evidence 18 iClicker Question As a planetary system and its star forms the temperature in the core of the nebula A Decreases in time B Increases in time C Remains the same over time D Cannot be determined 19 iClicker Question As a planetary system and its star forms the rate of rotation of the nebula A Decreases in time B Increases in time C Remains the same over time D Cannot be determined 20 The Formation of Earth • Planetesimals – Combined (accretion) to form earth • Great bombardment – Meteors – Growth of planet • 20 metric tons per day 21 Differentiation • Differentiation – Heat from collisions – Dense material sank to center – Lighter material rose to surface • Structure – Core – Mantle – Crust 22 Crust and Us 23 Earth’s Interior How We Know It 24 iClicker Question Which of the diagram represents the mantle of the Earth? A B C D E None of the above. 25 iClicker Question Which of the diagram represents the outer core of the Earth? A B C D E None of the above. 26 iClicker Question Energy transport from one region to another by the movement of material as in the mantle of the Earth is known as A chaos. B radiance. C conduction. D differentiation. E convection. 27 iClicker Question The existence of earthquake shadow zones indicates that there is an abrupt change between the properties of the mantle and those of the core. Specifically, the transverse wave shadow zone shows that the outer core must be A solid. B liquid or semi-liquid. C gaseous. D similar to crustal material. E impossible to determine. 28 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 29 Planetary Idiosyncracies • Cratering – Mercury, Mars, Moon – Few on Earth • weathering • Rotation – Venus – Earth’s axis – Uranus 30 The Evolution of Planetary Atmospheres • Earth’s atmosphere – Early – Outgassing • Atmosphere was N2, CO2, H2, & H2O – Gravitational escape – Living organisms 31 iClicker Question • All our observations of the Sun and planets have been made from the surface of the Earth. – – A B True False 32 iClicker Question • All planets and most of their moons orbit in the same direction around the Sun – – A B True False 33 iClicker Question • Almost all planets and moons rotate on their axes in the same direction as the planets orbit the Sun. – – A B True False 34 iClicker Question • What is the shape of our solar system? – – – A B C spherical (like a ball) flat (like a dish) tubular (like a hot dog) 35 iClicker Question • The mass in our solar system is evenly distributed. – – A B True False 36 Exploring the Solar System 37 The Inner Solar System • Mercury, Venus, Mars – Mercury and Venus too hot for life • Mars Exploration – Multiple missions – Found evidence of water 38 The Outer Solar System • Jupiter, Saturn, Uranus, Neptune – Layered structure – No solid surface • Jupiter – Comet Shoemaker-Levy 9 – Galileo spacecraft • Saturn – Cassini spacecraft 39 The Outer Solar System II 40 • Jupiter’s Moons – Io, Europa, Ganymede, Callisto and 63 others known • Saturn’s Moons – Titan, Mimas, Hyperion and about 59 (61?) others • Rings Moons and Rings – Ice and rock - more ice in Saturn’s rings 41 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) 42 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 43 The Launch of New Horizons Pluto Mission 17 Jan 2006 http://www.youtube.com/watch?v=KNJNaIoa5Hk 44 Io’s Volcanoes from New Horizons 45 46 Pluto 47 Pluto’s Methane (frozen) 48 Charon 49 Pluto 50 Pluto Atmosphere Detection 51 Pluto and Charon 52 Carbon Monoxide (Frozen) 53 Solar Wind at Pluto 54 Pluto “Heart” Region 55 Pluto Mountain Range 56 Nix and Hydra 57 Pluto, True Color 58 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 63 Planetary Summary Mass (Earth=1) Density (g/cm3) Major Constituents Mercury Venus Earth Mars 0.06 0.82 1.00 0.11 5.4 5.2 5.5 3.9 Rock, Iron Rock, Iron Rock, Iron Rock, Iron Jupiter Saturn 318 95 1.3 0.7 H, He H, He Uranus Neptune 14 17 1.3 1.7 Ices, H, He Ices, H, He Planet 64 iClicker Question • Mercury, Venus, Earth, and Mars are called: – – – – – A B C D E galaxial objects standard planetoids Jovian planets terrestrial planets dwarf planets 65 iClicker Question • Jupiter, Saturn, Uranus, and Neptune are called: – – – – – A B C D E galactic objects standard planetoids Jovian planets terrestrial planets dwarf planets 66 iClicker Question • The asteroid belt is located: – – – – A B C D between the Sun and Mercury between Mercury and Venus between Mars and Jupiter outside of our solar system 67 iClicker Question • Distinctive features of the solar system such as the rotation of the Sun, orbits of the planets, and the distribution of mass into one large central object and lots of much smaller orbiting bodies is explained by: – – – – A B C D the Hubble theory the nebular hypothesis the Trefil and Hazen gambit the relativity theory 68 iClicker Question • What are the Jovian planets primarily composed of? – – – – – A B C D E rocky substances element 119 (Jo) hydrogen and helium iron (Fe) silicon (Si) 69 iClicker Question • Outgassing and gravitational escape are processes by which – – – – A B C D planets form an atmosphere space travel may become possible solar systems form planets string theory can be applied 70 iClicker Poll Question • Have you ever seen a meteor or meteorite? – – – A B C yes no don’t know what these are 71 iClicker Poll Question • Should future missions to the planets carry people or robots? – – – – A People only B Robots only C People and robots D Neither, missions to planets are a waste of money 72