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Touring our Solar System
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Overview | Evolution of the planets | Planets: a brief tour | Minor members of the solar system | Links | top | Classes Home

Overview

  • Solar system includes
    • Sun
    • Nine planets and their satellites
    • Asteroids
    • Comets
    • Meteoroids
  • A planet's orbit lies in an orbital plane
    • Similar to a flat sheet of paper
    • The orbital planes of the planets are inclined
      • Planes of seven planets lie within 3 degrees of the Sun's equator
      • Mercury's is inclined 7 degrees
      • Pluto's is inclined 17 degrees
  • Two groups of planets occur in the solar system
    • Terrestrial (Earth-like) planets
      • Mercury through Mars
      • Small, dense, rocky
      • Low escape velocities
    • Jovian (Jupiter-like) planets
      • Jupiter through Neptune
        • Large, low density, gaseous
        • Massive
        • Thick atmospheres composed of hydrogen, helium, methane, and ammonia
        • High escape velocities
    • Pluto not included in either group
    • The planets drawn to scale
  • Planets are composed of :
    • Gases
      • Hydrogen
      • Helium
    • Rocks
      • Silicate minerals
      • Metallic iron
    • Ices
      • Ammonia (NH3)
      • Methane (CH4)
      • Carbon dioxide (CO2)
      • Water (H2O)
Overview | Evolution of the planets | Planets: a brief tour | Minor members of the solar system | Links | top | Classes Home

Evolution of the planets

  • Nebular hypothesis
    • Planets formed about 5 billion years ago
    • Solar system condensed from a gaseous nebula
    • Nebular hypothesis - aka “Big Bang Theory”
  • As the planets formed, the materials that compose them separated
    • Dense metallic elements (iron and nickel) sank toward their centers
    • Lighter elements (silicate minerals, oxygen, hydrogen) migrated toward their surfaces
    • Process called chemical differentiation
  • Due to their surface gravities, Venus and Earth retained atmospheric gases
  • Due to frigid temperatures, the Jovian planets contain a high percentage of ices

Overview | Evolution of the planets | Planets: a brief tour | Minor members of the solar system | Links | top | Classes Home


Planets: a brief tour

  • Earth's Moon
    • General characteristics
      • Diameter of 3475 kilometers (2150 miles) is unusually large compared to its parent planet
      • Density
        • 3.3 times that of water
        • Comparable to Earth's crustal rocks
      • Perhaps the Moon has a small iron core
      • Gravitational attraction is one-sixth of Earth's
      • No atmosphere
      • Tectonics no longer active
      • Surface is bombarded by micrometeorites from space which gradually makes the landscape smooth
    • Lunar history
      • Hypothesis suggests that a giant asteroid collided with Earth to produce the Moon
      • Older areas have a higher density
      • Younger areas are still smooth
      • Moon evolved in three phases
        • (1) Original crust (highlands)
          • As Moon formed, its outer shell melted, cooled, solidified, and became the highlands
          • About 4.5 billion years old
        • (2) Formation of maria basins
          • Younger than highlands
          • Between 3.2 and 3.8 billion years old
        • (3) Formation of rayed craters
          • Material ejected from craters is still visible
          • e.g., Copernicus (a rayed crater)
          • Major topographic features on the lunar surface
    • Lunar surface
      • Two types of terrain
        • Maria (singular, mare), Latin for "sea"
          • Dark regions
          • Fairly smooth lowlands
          • Originated from asteroid impacts and lava flooding the surface
          • Formation of lunar maria
        • Highlands
          • Bright, densely cratered regions
          • Make up most of the Moon
          • Make up all of the "back" side of the Moon
          • Older than maria Earth's Moon
      • Craters
        • Most obvious features of the lunar surface
        • Most are produced by an impact from a meteoroid which produces
      • Ejecta
        • Occasional rays (associated with younger craters)
        • A 20-kilometer-wide crater on the Moon
      • Lunar regolith
        • Covers all lunar terrains
        • "Soil-like" layer produced by meteoric bombardment
        • Composed of
          • Igneous rocks
          • Breccia
          • Glass beads
          • Fine lunar dust
  • Planets: a brief tour
  • Mercury
    • Innermost planet
    • Second smallest planet
    • No atmosphere
    • Cratered highlands
    • Vast, smooth terrains
    • Very dense
    • Revolves quickly
    • Rotates slowly
    • Photomosaic of Mercury
  • Venus
    • Second to the Moon in brilliance
    • Similar to Earth in
      • Size
      • Density
      • Location in the solar system
    • Shrouded in thick clouds
      • Impenetrable by visible light
    • Atmosphere is 97% carbon dioxide
      • Surface atmospheric pressure is 90 times that of Earth's
    • Surface
      • 80% of surface is subdued plains that are mantled by volcanic flows
      • Low density of impact craters
      • Tectonic deformation must have been active during the recent geologic past
      • Thousands of volcanic structures
    • Computer generated view of Venus
  • Mars
    • Atmosphere
      • 1% as dense as Earth's
      • Primarily carbon dioxide
    • Cold polar temperatures (-193ºF)
    • Polar caps of water ice, covered by a thin layer of frozen carbon dioxide
    • Extensive dust storms with winds up to 270 kilometers (170 miles) per hour
    • A picture of the Martian landscape from the Viking 1 lander
    • Surface
      • Numerous large volcanoes – largest is Mons Olympus
      • Less-abundant impact craters
      • Tectonically dead
      • Several canyons
        • Some larger than Earth’s Grand Canyon
        • Valles Marineras – the largest canyon
      • Mons Olympus, an inactive shield volcano on Mars
      • The Valles Marineris canyon system on Mars
      • "Stream drainage" patterns
        • Found in some valleys
        • No bodies of surface water on the planet
        • Possible origins
          • Past rainfall
          • Surface material collapses as the subsurface ice melts
    • Moons
      • Two moons
        • Phobos
        • Deimos
        • Captured asteroids
    • Current Findings:
      • “Blueberries” – hematite concretions
      • Layered Rocks
      • Cross bedding and ripple marks
      • Hematite
  • Jupiter
    • Largest planet
    • Very massive
      • 2.5 more massive than combined mass of the planets, satellites, and asteroids
      • If it had been ten times larger, it would have been a small star
    • Rapid rotation
      • Slightly less than 10 hours
      • Slightly bulged equatorial region
    • Artist’s view of Jupiter with the Great Red Spot visible
    • Banded appearance
      • Multicolored
      • Bands are aligned parallel to Jupiter's equator
      • Generated by wind systems
      • Great Red Spot
        • In planet's southern hemisphere
        • Counterclockwise rotating cyclonic storm
    • Structure
      • Surface thought to be a gigantic ocean of liquid hydrogen
      • Halfway into the interior, pressure causes liquid hydrogen to turn into liquid metallic hydrogen
      • Rocky and metallic material probably exists in a central core
    • Moons
      • At least 28 moons
      • Four largest moons
        • Discovered by Galileo (Galilean satellites)
        • Callisto - outermost Galilean moon
        • Europa - smallest Galilean moon
        • Ganymede - largest Jovian satellite
        • Io - innermost Galilean moon and is also volcanically active
          • Close-ups of Io (false color)
          • A volcanic eruption on Io June 28, 1997 (Galileo spacecraft)
            • This mosaic of images collected by NASA's Galileo spacecraft on November 25,1999 shows a fountain of lava spewing above the surface of Jupiter's moon Io.Planets: a brief tour
  • Saturn
    • Similar to Jupiter in its
      • Atmosphere
      • Composition
      • Internal structure
    • Rings
      • Most prominent feature
      • Discovered by Galileo in 1610
      • Composed of small particles (moonlets) that orbit the planet
      • Most rings fall into one of two categories based on particle density
      • Thought to be debris ejected from moons
      • The ring system of Saturn
    • Planets: a brief tour
    • Saturn
    • Other features
      • Dynamic atmosphere
      • Large cyclonic storms similar to Jupiter's Great Red Spot
      • Thirty named moons
        • Titan – the largest Saturnian moon
          • Second largest moon (after Jupiter's Ganymede) in the solar system
          • Has a substantial atmosphere
  • Uranus
    • Uranus and Neptune are nearly twins
    • Rotates "on its side"
    • Rings
    • Large moons have varied terrains
  • Neptune
    • Dynamic atmosphere
      • One of the windiest places in the solar system
      • Great Dark Spot
      • White cirrus-like clouds above the main cloud deck
    • Eight satellites
      • Triton – largest Neptune moon
        • Orbit is opposite the direction that all the planet's travel
        • Lowest surface temperature in the solar system (-391ºF)
        • Atmosphere of mostly nitrogen with a little methane
        • Volcanic-like activity
        • Composed largely of water ice, covered with layers of solid nitrogen and methane
  • Pluto
    • Not visible with the unaided eye
    • Discovered in 1930
    • Highly elongated orbit causes it to occasionally travel inside the orbit of Neptune, where it resided from 1979 thru February 1999
    • Moon (Charon) discovered in 1978
    • Average temperature is -210ºC

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Minor members of the solar system

  • Asteroids
    • Most lie between Mars and Jupiter
    • Small bodies – largest (Ceres) is about 620 miles in diameter
    • Some have very eccentric orbits
    • Many of the recent impacts on the Moon and Earth were collisions with asteroids
    • Irregular shapes
    • Origin is uncertain The orbits of most asteroids lie between Mars and Jupiter
    • Image of asteroid 951 (Gaspra)
  • Comets
    • Often compared to large, "dirty snowballs"
    • Composition
      • Frozen gases
      • Rocky and metallic materials
    • Frozen gases vaporize when near the Sun
      • Produces a glowing head called the coma
      • Some may develop a tail that points away from Sun due to
        • Radiation pressure and the
        • Solar wind
      • Orientation of a comet’s tail as it orbits the Sun
    • Origin
      • Not well known
      • Form at great distance from the Sun
    • Most famous short-period comet is Halley's comet
      • 76 year orbital period
      • Potato-shaped nucleus (16 km by 8 km)
    • Comet Hale-Bopp
  • Meteoroids
    • Called meteors when they enter Earth's atmosphere
    • A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet's path
    • Meteoroids are referred to as meteorites when they are found on Earth
    • Types of meteorites classified by their composition
      • Irons
        • Mostly iron
        • 5-20% nickel
      • Stony
        • Silicate minerals with
        • Inclusions of other minerals
      • Stony-irons – mixtures
      • Carbonaceous chondrites
        • Rare
        • Composition - simple amino acids and other organic material
      • May give an idea as to the composition of Earth's core
      • Give an idea as to the age of the solar system
Overview | Evolution of the planets | Planets: a brief tour | Minor members of the solar system | Links | top | Classes Home


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