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Pic/Puzzle of the Day & Announcements for Nov 3, 2008

Pic/Puzzle of the Day & Announcements for Nov 3, 2008. Quiz #4: Wednesday. HW4 solns: Posted later today. Other: Office hours today, until 3 (other by appt) Guest Lecture on Mars! (Wednesday/Monday). Today:. 1. Geology of Mercury & Venus 2. Venusian Atmosphere

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Pic/Puzzle of the Day & Announcements for Nov 3, 2008

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  1. Pic/Puzzle of the Day & Announcements for Nov 3, 2008 Quiz #4: Wednesday HW4 solns: Posted later today • Other: Office hours today, until 3 • (other by appt) • Guest Lecture on Mars! (Wednesday/Monday)

  2. Today: 1. Geology of Mercury & Venus 2. Venusian Atmosphere 3. Earth vs. Venus - This planet is TOO HOT

  3. Mercury - An “Extreme” Planet • Closest Planetto the Sun • 0.38 AU, 2.5 x closer than Earth • sunlight is 6.25 x more intense! • Highest Density other than Earth • Largest Temperature Swings • more than 1000 F! • Interesting Rotation • Global Magnetic Field

  4. Mercury in the Sky • Closest Planetto the Sun • Hard to observe What time of day is Mercury observable?

  5. Mercury - Early Observations • Closest Planetto the Sun • Hard to observe (imagination required!) Giovanni Schiaparelli (1835-1910) • Mercury Rotates Slowly • Synchronous? • T?

  6. Mercury - Synchronous Rotation? 1962 - Radiation from Mercury not so cold X Not Synchronous 1965 - Dyce & Pettengill DOPPLER EFFECT How??

  7. Mercury - Synchronous Rotation? 1962 - Radiation from Mercury not so cold X Not Synchronous 1965 - Dyce & Pettengill Rotation Period = 59 Days (Orbital Period = 88 Days)

  8. Earth rotates on its axis ~365 times for each revolution around the Sun Mercury rotates on its axis exactly 1.5 times for each revolution around the Sun (3:2 spin-orbit resonance) How long is a day on Mercury? Rotation Period = 59 Days (Orbital Period = 88 Days) 1 day on Mercury = 176 Earth days Longer than 1 year!

  9. ? Mercury & Einstein Observation: Mercury’s Orbit Precesses General Relativity! Space is curved by Sun’s mass! WHY??

  10. Mercury - Overview Planet of Extremes

  11. Large iron core Small Magnetic Field (1% Earth) Mercury - Spacecraft data Mariner 10: Venus/Mercury flyby (1974) Flew by 3x before it ran out of fuel! Imaged 45% of surface Calculated HIGH density (4.4g/cm3)

  12. Mercury’s Magnetic Field - Why? Small Magnetic Field (1% Earth) 2007 - Mercury has a small molten core!

  13. Mercury - Spacecraft data Messenger - Recent close approach Feb. 1 & Oct. 6, 2008! Mercury orbit - March 18, 2011

  14. Messenger Terrain South Pole

  15. Messenger Terrain - Similar to Moon!

  16. Mercury - Surface Features Heavily Cratered Areas - Old (Heavy Bombardment) Large smooth Basins - Younger, Lava from Large impacts?

  17. Mercury - Surface Features Messenger Images

  18. Mercury - Surface Features Caloris Basin - largest feature on Mercury -size of Texas -jumbled terrain opposite -caused by large impact

  19. Mercury - Surface Features Scarps: Large cliffs caused by contraction of surface -3 km high -100s of km across -contraction from cooling (planet shrank by ~20km!) -closed off volcanic vents

  20. Mercury - Unsolved Mysteries - “Mysterious dark blue material??” -Ice on Poles? -size of molten core?

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