Lecture 16: The Solar System

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    • Date: November 2, 1994
    Reading Assignment: pp. 198-201

    Description : overview of the solar system

    Objectives

  • be able to name the planets in their order from the Sun
  • understand the differences between gas giants and terrestrial planets
  • be able to explain the Titus-Bode relationship
  • understand 3 ways of determining a planet's mass
  • be able to describe what factors influence the formation of a planet's atmosphere
  • be able to describe how results from lunar exploration allow us to date the age of planetary surfaces

    • Lecture Outline

    Slide # 1: Lecture 16: The Solar System- The Big Picture

  • sizes and scales
  • a tour of the neighborhood
  • atmospheres, gravity, and heat
  • young and old surfaces
    • Slide # 2: Lecture 15: The Moon
  • bulk properties
  • surface features
  • impact craters
  • surface composition
  • volcanos
  • interior
  • origin
  • exploration
    • Slide # 3: Planetary Structure
  • core
  • mantle
  • crust
  • hydrosphere
  • atmosphere
  • magnetosphere
    • Slide # 4: Sizes and Scales
  • a scale model of the solar system
    • Slide # 5: Big Planets
  • the larger Planets
    • Slide # 6: Terrestrial Planets and Moons
  • smaller planets and moons
    • Slide # 7: Planetary Orbits
  • outer solar system
    • Slide # 8: Planetary Orbits
  • inner solar system
    • Slide # 9: Titus-Bode
  • a numerical series that matches planetary distances
  • not a true physical law
    • Slide # 10: Titus-Bode
  • start with 0.4
  • add the following numbers
  • 0.0 Mercury
  • 0.3 Venus
  • 0.6 Earth
  • 1.2 Mars
  • 2.4 Asteroid Belt
  • 4.8 Jupiter
  • 9.6 Saturn
  • example:Jupiter should be about 4.8 + 0.4 = 5.2 AU from the Sun
    • Slide # 11: Titus-Bode
  • what does it mean?
  • probably just an chance numerical series
  • does not work well for Neptune
    • Slide # 12: The Solar System Inventory
  • the Sun- 99.85% of the mass
  • Planets
  • Moons
  • Asteroids
  • Comets
  • dust, solar wind, meteroids
    • Slide # 13: Planets and Moons
  • Terrestrial- rocky
  • Earth, Venus, Mars, Mercury
  • Jovian- Gas Giants
  • Jupiter, Saturn, Neptune, Uranus
  • Rocky Moons
  • the Moon, Io, Ceres
  • Icy Moons
  • Pluto, Europa, Callisto
    • Slide # 14: Moons
  • Mercury, Venus - none
  • Earth - 1
  • Mars - 2
  • Jupiter - 16
  • Saturn - 18
  • Uranus - 15
  • Neptune - 8
  • Pluto - 1
    • Slide # 15: Solar System Debris
  • Asteroids
  • small, rocky bodies
  • usually found between Mars and Jupiter
  • Comets
  • small, icy bodies
  • usually found when they pass near the Sun
    • Slide # 16: Planetary Mass
  • how do you determine the mass of a planet?
    • Slide # 17: Determining a PlanetŐs Mass
  • satellite orbits and KeplerŐs law
  • P2 = k a3 for any orbiting object
  • mass determines the constant k
  • observations of planetary perturbation
  • planets slightly influence each otherŐs orbits
    • Slide # 18: Determining a PlanetŐs Mass
  • asteroid and comet orbits
  • observe how a planet changes an asteroid or comet orbit
  • spacecraft
  • observe how a planet changes the path of a spacecraft
    • Slide # 19: Planetary Masses
  • Mercury = 1/20
  • Venus = 4/5
  • Earth = 1
  • Mars = 1/9
  • Jupiter = 318
  • Saturn = 95
  • Uranus = 15
  • Neptune = 17
  • Pluto = 0.002
    • Slide # 20: Atmospheres
  • Why does the Earth have an atmosphere?
  • Why doesnŐt the have an atmosphere?
    • Slide # 21: Atmospheres- Gravity
  • determines the escape velocity
  • speed needed to escape the planetŐs gravity
  • high mass planets have high escape velocities
    • Slide # 22: Atmospheres- Temperature
  • determines the average molecular energy
  • high temperature means faster molecular motion
    • Slide # 23: Atmospheres- Molecular Weight
  • determines the average molecular speed
  • low mass molecules have high speeds
    • Slide # 24: Atmospheres- Earth
  • medium mass planet
  • escape velocity = 11 km/s
  • medium temperature
  • 300 K
  • gas mass
  • Nitrogen and Oxygen cannot escape
  • Hydrogen and Helium escape
    • Slide # 25: Atmosphere- The Moon
  • low mass planet
  • 2 km/s escape velocity
  • medium temperature
  • 260 K (average)
  • gas mass
  • all gases escape
    • Slide # 26: Atmosphere- Jupiter
  • very massive planet
  • escape velocity high
  • low temperature
  • 125 K
  • gas mass
  • No gases escape
    • Slide # 27: Atmospheres
  • molecular speed and escape velocity
    • Slide # 28: Craters
  • the main cause of Erosion on the Moon
  • why is it important on the Moon?
  • no atmosphere
  • no other source of erosion
  • no plate tectonics and no new surface
    • Slide # 29: Dating Lunar Terrain
  • relative ages can be deduced from cratering
  • crater density = # craters per square km
  • high crater density = old surface
    • Slide # 30: A Sharp Decline in Cratering
  • most cratering ended 3.9 billion years ago
  • some continues today, but at a VERY low rate
    • Slide # 31: Planetary Surfaces
  • crater density tells us surface ages
  • can be used without landing on the planet
    • Slide # 32: Comparative Planetology
  • helps us understand the origin of the solar system
  • helps us understand Earth