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Sept. 14, 2011: 10am Class

Sept. 14, 2011: 10am Class. Please complete Quiz #3 on d2l before Friday, Sept. 16 Star Party on Sunday, Sept. 18. Instructions will be emailed to those who signed up, including Constellation Exercise. Don’t forget: Starry Night HW (due next Wed), Telescope Lab

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Sept. 14, 2011: 10am Class

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  1. Sept. 14, 2011: 10am Class • Please complete Quiz #3 on d2l before Friday, Sept. 16 • Star Party on Sunday, Sept. 18. Instructions will be emailed • to those who signed up, including Constellation Exercise. • Don’t forget: Starry Night HW (due next Wed), • Telescope Lab • FIRST MIDTERM: Monday, Sept. 26 (details later) • Today: Formation of the Solar System; Mercury & Venus

  2. What have we learned about the solar system? • What does the solar system look like? • Planets orbit Sun in the same direction and in nearly the same plane. • What can we learn by comparing the planets to one another? • Comparative planetology looks for patterns among the planets. • Those patterns give us insight into the general processes that govern planets. • Studying other worlds in this way tells us about our own planet.

  3. What are the major features of the Sun and planets? The planets are very small compared to the distances between them. The planets of the inner solar system are rocky and have few moons (Mercury, Venus, Earth & Mars) The planets of the outer solar system are gaseous and have many moons and rings (Jupiter, Saturn, Uranus, Neptune) Pluto is a member of the Kuiper Belt – a “dwarf planet” or “Trans-Neptunian Object (TNO)

  4. Formation of the Solar System (1) The Solar System formed from the collapse of a big cloud of gas (nebula) (2) The collapse and contraction of the gas  heated up (3) CONSERVATION OF ANGULAR MOMENTUM caused the gas to spin faster and faster Rapid collapse along poles, centrifugal forces slow the collapse along equator  Spinning disk When the density of the core got high enough, fusion of H  He began: The Sun started to shine

  5. (6) “Planetesimals” formed (clumps of rock and ice) in • the spinning disk, collided and coalesced. • (7) In the early solar system, there were many collisions, • causing lots of craters. • (8) Planetesimals coalesced to form the planets & moons

  6. Conservation of Angular Momentum caused the gas to form a spinning disk.

  7. The Spinning Skater

  8. Many collisions  orbits tend to be circular objects that are not in circular orbits collide more

  9. (10) Inside the “FROST LINE” it was warm and the H, He remained gaseous  Terrestrial planets Outside the “FROST LINE” it was cold and planets have huge gaseous, icy atmosphere  gas giants

  10. Mercury

  11. Facts about Mercury • Closest planet to the Sun • Heavily cratered • Dead volcanoes • Virtually no atmosphere • 10-12 Earth atms; Oxygen, Sodium, Hydrogen • Not enough gravity to hold atmosphere • Relatively poorly studied: • Mariner Fly-by 1974-1975 • Messenger arrived in March 2011 • Mercury’s Diameter: 4878 km, or 0.382 Earth diameters • Mercury’s Mass: 3.3 x 1023 kg, or 0.055 Earth masses

  12. Mercury compared to other planets and moons

  13. More facts about Mercury • Resonant Rotation • Mercury rotates 3 times for every two orbits around the Sun • Rotation rate: 59 Earth days • Orbit: 88 Earth days • The net effect is that noon (Sun directly overhead) occurs once for every two times Mercury orbits the Sun (every 176 days) • So the Sun is “up” in the sky for 3 Earth months, then there are 3 months of darkness • Axis of rotation is not tilted with respect to the ecliptic

  14. Montage from Mariner Fly-by 1974-1975; 125,000 miles from surface

  15. Messenger, 2011

  16. Caloris Basin

  17. Impact Craters

  18. Impact Craters After the impact, the material directly below the impactor is vaporized and melted. Material from about 1/3 the crater depth is ejected onto the surface The 2/3 of the material below the ejected layer is crushed and displaced downward, forming an ejecta blanket

  19. Bright rays: Ejecta from craters

  20. Fault Lines

  21. Double Ringed Crater

  22. Mercury: has molten core, weak magnetic field Mercury’s magnetic field strength is 1% of the magnetic field strength of the Earth

  23. Venus

  24. Facts about Venus • Diameter = 0.948 Earth diameters • Mass = 0.82 Earth masses • Distance from the Sun = 0.72 Astro Units • Length of day: 243 Earth days • Length of year: 225 Earth days • Axis of rotation inclined 177 degrees • Rotates RETROGRADE

  25. Most interesting fact about Venus • VERY thick atmosphere • Atmospheric pressure at surface = 90x Earth’s • Atmos. Composition: • 96.5% Carbon Dioxide (CO2) • 3.5% Nitrogen molecules (N2) • Clouds of sulfur dioxide • Lightening

  26. Heavy atmosphere Runaway Greenhouse effectExtremely hot on surface • Surface of Venus T = 900 F • Hot enough to melt lead

  27. First exploration of surface of Venus: Soviet Union’s Venera 13 landed, March 1982

  28. Magellan Radar Mapping ofSurface of Venus (1989-1993) Rich geology: Volcanos

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