Lecture2 - The solar system and the origin of Earth Solar...

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Unformatted text preview: The solar system and the origin of Earth Solar System Consists of our star, the sun, the planets, their satellites, and asteroids Located on the arm of a very large spiral galaxy Within the Milky Way galaxy 1 Geocentric Perspective Proposed by Aristotle (384-322 BCE) Geocentric universe deeply entrenched in church doctrine But, was challenged by Aristarchus (312-230 BCE) Simple spheres containing the planets and the sun revolving around Earth did not explain the retrograde motion of planets Retrograde Motion 2 Geocentric Perspective Ptolemy (150 CE) proposed that planets also follow a smaller circular orbit (epicycles) predictable periods of retrograde motion Retrograde Motion Copernicus (1473-1543) suggested that because Mars has the larger retrograde motion it is the closest to Earth while Saturn, having the smallest retrograde motion is the furthest from the Earth proposed that the Earth spins on its axis leading to sunrise and sunset 3 Kepler (1571-1630) 1) law of ellipses The orbit of each planet is an ellipse with sun at one focus 2) law of orbital harmony For any planet, the square of the orbital period in years is proportional to the cube of the planet’s average distance from the sun 3) law of equal areas 3) law of equal areas A line drawn from a planet to the sun sweeps out equal areas in equal time The orbital velocity changes 4 4th century BCE 17th century CE Compared to astronomy, geology is a very 'young' science le! a sc o tt o sn e nc ta dis 12,756 km diameter of Earth 142,800 km diameter of Jupiter 1,400,000 km diameter of the Sun International Astronomical Union, 2006 proposal 5 Scaled-down representation of the solar system Let’s shrink the solar system such that the distance of the Sun to Pluto (5.9 x 109 km) is 100 m At this scale, the Sun’s diameter of 1,400,000 km reduces to a 2.4 cm wooden ball red super giant Scaled-down model of solar system SUN Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Distance 0m 1.0 m 1.8 m 2.5 m 3.9 m 13.2 m 24.2 m 48.6 m 76 m 100 m Diameter 2.4 cm 0.008 cm 0.02 cm 0.02 cm 0.01 cm 0.24 cm 0.20 cm 0.09 cm 0.08 cm 0.004 cm 6 Mercury, d = 4,880 km, ρ = 5.4 g/cm3 Messenger, 2011 NASA scarps? 0 satellites • 70% metallic & 30% silicate composition; internally layered • largest T range (-170° to 425°C) Venus, d = 12,104 km, ρ = 5.24 g/cm3 Magellan radar 0 satellites image, NASA • Earth's twin; volcanoes, tectonics • thick (deadly) atmosphere (inhibits telescope observation) 7 Earth, d = 12,760 km, ρ = 5.52 g/cm3 1 satellite Apollo 8, 25-DEC-1968, NASA Moon, d = 3475 km, ρ = 3.3 g/cm3 Impact theory of formation during initial spiralling of nebula 8 Highlands: • 90% plagioclase feldspar • "foam" on magma ocean Maria: • flood basalts Maria Highlands Moon evolution: • formation of crust • lunar highlands • maria basins • rayed craters Mars, d = 6,787 km, ρ = 3.96 g/cm3 polar ice Hubble space telescope, MAR-2001, NASA 2 satellites • ancient volcanoes & tectonics; internally layered; crust: basalt 9 Jupiter, d = 143,000 km, ρ = 1.33 g/cm3 layered atmosphere; giant storms 63 satellites + moonlets surface is liquid hydrogen Cassini mission, 7-DEC-2000, NASA-ESA core region is surrounded by dense metallic hydrogen, which extends outward to about 78% of the radius of the planet Io, one of the four Galilean satellites • currently volcanically active • melting is from tidal energy Galileo mission, 3-JUL-1999, NASA 10 Volcanic plumes on Io fountains of lava gushing 160 km in height Galileo mission, 28-JUN-1997, NASA Saturn, d = 121,000 km, ρ = 0.69 g/cm3 Cassini mission, 7-MAY-2004, NASA-ESA rings: <100 m thick 56 satellites + moonlets Core similar to Earth surrounded by a deep layer of metallic hydrogen an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer; magnetic field 11 Titan (moon): (liquid) lakes and seas + atm! The Twins ice dominating over gases = Ice Giants a rocky center, an icy mantle and an outer gaseous hydrogen/helium envelope; ice: water, ammonia and methane Uranus, d = 51,000 km, ρ = 1.27 g/cm3 27 satellites axis of rotation Neptune, d = 49,500 km, ρ = 1.76 g/cm3 13 satellites; Triton contains cryovolcanism 12 DEMOTED ! Pluto, d = 2,300 km, ρ = 2.3 g/cm3 largest member of a distinct population of rock, metals, and ices called the Kuiper belt (dwarf planets, moons, planetesimals) Terrestrial vs Jovian planets • hard silicate rocky surfaces • dense metallic cores • close to the Sun • few satellites • larger ones have atmospheres 13 Terrestrial vs Jovian planets • very large outer planets • very low density • turbulent • many satellites • composed of gases, H, He, NH3 Comet Hale-Bopp asteroids: leftover planet fragments comets: dirty snowballs meteoroids: shooting stars (iron & stony) ionized gases dust 14 Wanapitei crater, ON, 37 Ma Manicouagan crater, QC, 214 Ma Charlevoix crater, QC, 342 Ma Sudbury crater, ON, 1850 Ma Sudbury crater, ON, 1850 Ma nickel, copper, platinum, palladium, gold 15 Chicxulub crater Age of solar system • Meteorites 4.53 to 4.58 Ga • Moon rocks 4.4 to 4.5 Ga • Oldest rock on Earth, Acasta gneiss in NWT is 4.03* Ga (but Earth is tectonically active, rocks keep getting recycled…) • Oldest mineral on Earth, zircon in Australia is 4.4 Ga *4.28 Ga in N. Quebec; highly controversial Ma = mega-annum = millions of years = 106 years Ga = giga-annum = billions of years = 109 years 16 Solar nebula theory Some observations to consider… All planets revolve around the Sun in the same direction (ccw when viewed from top, i.e. Earth north). All planets revolve within the same plane (ecliptic) except for Pluto (17° tilted from the ecliptic). Nearly all planets revolve ccw on their axes (Venus is cw, Uranus is severely tilted). Solar nebula theory Some observations to consider… Sun also revolves ccw on its axis (25½ Earth days). Axes of rotation of sun and planets are nearly all ⊥ to the ecliptic. Terrestrial planets have high density, ρ = 4 to 5.5 g/cm3, rocky surfaces with metallic cores. Jovian planets have low density, ρ = 0.6 to 1.8 g/cm3, composed of H, He, NH3, CH3. 17 Solar nebula theory • Solar nebula, cloud of He, H, some heavier dust • 4.6-4.4 Ga ago, gravitational contraction, cloud initiates rotation • Gravitational collapse, increase T, light elements driven towards outer edges of disk • Planets result from accretion of dust, planetisimals • Sun originates from concentration of mass at the centre Solar nebula theory A few problems: • Venus rotates cw, contrary to the majority of planets • Origin of the asteroid belt (between Mars and Jupiter), destruction of an early planet by collision or failed accretion of planetisimals? • Rotation speed of Sun is too slow given its position at the centre of the disk. 18 Earth Systems • Sense of immense scale of solar system • Difference between Terrestial and Jovian planets, and what drives that is a difference • Similar geologic processes operating on other planets • Understanding of nebula theory Earth Systems Read chapters 1, 2 & 12 for Monday 19 Terrestrial vs Jovian planets Terrestrial vs Jovian planets 20 ...
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This note was uploaded on 03/26/2012 for the course GEO 1111 taught by Professor Dumas during the Winter '09 term at University of Ottawa.

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