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Earth-rise on Moon

Earth-rise on Moon. The Moon. Apollo and Luna Landing Sites. A15. A17. L24. L20. L16. A11. A12. A14. A16. Lunar Surface – Sandy and Rocky. The Moon: Some Factoids. Lunar exploration: Luna series (USSR), Surveyor (US) unmanned missions Apollo manned missions explored geology

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Earth-rise on Moon

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  1. Earth-rise on Moon

  2. The Moon

  3. Apollo and Luna Landing Sites A15 A17 L24 L20 L16 A11 A12 A14 A16

  4. Lunar Surface – Sandy and Rocky

  5. The Moon: Some Factoids • Lunar exploration: Luna series (USSR), Surveyor (US) unmanned missions • Apollo manned missions explored geology • Density = 3.34 g/cc ; composition? • D (Earth, Mercury,Venus) = 5.52, 5.43, 5.24 g/cc  Composition? • Basic surface and interior similar to rocky part of the Earth (little or no metallic core or magnetic field)

  6. Highlands and Marias • Highlands were heavily cratered during the early history, from formation to about 4 billion years ago • Marias (dried up lava oceans) formed later, about 3 billion years ago

  7. Cratered Highlands and Marias Highlands are much older than marias. Why?

  8. Evolution of highlands and maria

  9. Craters and chronology (age) • Highlands are highly cratered regions that must be older than smoother regions of surface since most cratering activity was at the time of the formation of the solar system • Marias are much younger, and evolved later at places where large crater impact basins were formed and filled with lava from the interior

  10. Atmospheres and Surfaces • Lack of atmosphere - results in extreme temperatures - exposes surface to meteoroid impact  craters - lack of current geological activity and evolution (ceased long time ago) • Moon and Mercury lack atmosphere (too small and too close to the Sun) • Both have similar surface geology  craters and marias

  11. Formation of a lunar sea: Impact of meteoroid  Impact Basin  Filled with Lava  Maria

  12. A Mare

  13. Maria – Lightly cratered smooth surface

  14. Lava River

  15. Lunar Geology

  16. Formation of Moon • No generally accepted theory: three scenarios - Accretion - Fission (breakup) - Capture Possibly a combination

  17. Formation of Moon

  18. Earth Tides on Moon Tidal forces due to the Earth forced the Moon to rotate at the same rate as Its revolution; therefore it keeps the same face towards the Earth

  19. Another view of Moon ? And, Mercury !

  20. Mariner Fly-By’s Several orbital reconnaissance satellites, but no space probes landed yet

  21. The 2nd spacecraft to visit Mercury: MESSENGER (MErcury Surface, Space Environment, GEochemistry, and Ranging) Launched August 2004, reached Mercury orbit March 2011.

  22. Best Mercury Sighting at MaximumWestern Elongation Eccentric orbit implies different maximum angles

  23. Greatest Elongations of MercuryOptimum Mercury Sighting at Maximum Elongation, and/or just after sunset or before sunrise NOT easily seen, like Venus as “evening star”: Mercury is too small, too close to the Sun, and lacks atmosphere and hence has small albedo

  24. Mercury – Basic Statistics • Mass ~ 1/20 Earth’s • Diameter ~ 1/3 “ • Density ~ 5.5 g/cc • Year ~ 88 Earth days • Day ~ 59 “ • 0.4 AU from the Sun • Surface T: Day  700 F, Night  -300F

  25. Mariner Fly-By Picture Mosaic

  26. Cratered highlands of Mercury

  27. Mercury enigmas investigated by MESSENGER: Mercury has a huge impact crater called Caloris Basin. Diameter of crater = 1500 km Diameter of impacting asteroid = 100 km

  28. Mercury – Basic Features • Metal ball (mostly iron) surrounded by heavily cratered rocky crust like Moon • But weak magnetic field, why? • No molten, moving core! • Only refractory elements; volatile elements evaporated • Geology like the Moon, e.g. Caloris basin resembles lunar maria – large crater impact basin flooded later with lava • No Plate Tectonics, why?

  29. Interiors of Earth and Mercury

  30. Dopper Radar measurement of rotation speed of Mercury

  31. Aracebo Radio Telescope(Puerto Rico)

  32. A “Day” on Mercury • A year is the period of revolution (orbit) around the Sun • Two kinds of “day” on a planet: Sidereal and Solar • Sidereal day is the actual period of rotation on its axis (viewed with respect to the stars, not the Sun) • Solar day is the period of rotation with respect to the Sun • On the earth: solar day = 24 hrs, longer than sidereal day by 4 mins. • Mercury’s sidereal day is 2/3 of a Mercury year

  33. Rotation and Revolution of Mercury:Day and Year • Rotation period ~ 2/3 revolution period • A solar day is twice as long as a year !! • Solar Day (176 d) = 2 x Sidereal year (88 d) • Wait two years to see the sun in the same place in the sky (on the earth it is just 1 solar day, or 1 sidereal day + 4 mins) • What’s going on?

  34. Rotation and Revolution of Mercury Moon’s rotation period equals orbital period: see only one side or face of Moon Like the Moon Periods of Mercury Strong Tides due to Sun A solar day on Mercury is twice as long as the sidereal year

  35. Hot Poles on the Equator ! • Perihelion of Mercury is 1.5 times closer than aphelion • Mercury receives 2.25 times more solar energy at perihelion than at aphelion • Two extremities of the equator pointing towards the sun constitute two hot ‘thermal’ poles • Largest variation in temperature between day/night, but maximum temperature ~700 F is still less hot than Venus (> 800 F)

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