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MERCURY

MERCURY. The Innermost Planet. Conjunction. Inferior conjunction – inferior planet and Earth on same side of Sun Superior conjunction – inferior planet and Earth on opposite sides of Sun. Mercury ☿. Smallest of the planets (Pluto etc. does not count)

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MERCURY

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  1. MERCURY The Innermost Planet

  2. Conjunction • Inferior conjunction – inferior planet and Earth on same side of Sun • Superior conjunction – inferior planet and Earth on opposite sides of Sun

  3. Mercury ☿ Smallest of the planets (Pluto etc. does not count) Named for the swift messenger to the Roman gods

  4. Little is known about Mercury • Bright in appearance but not easily seen: • Only visible at morning or evening • At most, 28.3º from the Sun • Ground based telescopes give only limited detail

  5. Mercury – Physical Properties

  6. Mercury’s Orbit Long thought to be tidally locked to the Sun; measurements in 1965 showed this to be false. Mercury’s day and year are in a 3:2 resonance; Mercury rotates three times while going around the Sun twice. Spin-orbit resonance – ratio of the periods can be expressed as simple integers

  7. Mercury’s Orbit most eccentric orbit of all the planets orbit is inclined by 7 degrees to the plane of the ecliptic axial tilt is almost zero

  8. Transits • when Mercury comes between the Sun and the Earth • Mercury is seen as a small black dot moving across the face of the Sun • 2016 May 9

  9. Interior of Mercury • Crust • Mantle • Core • Core occupies 42% of Mercury (17% for Earth) • Has higher iron content

  10. Compared to Luna Mercury is much denser than the Moon Has a magnetic field – not well understood!

  11. Mercury’s Magnetosphere • Significant for size • Planetwide • Dynamo effect? • MESSENGER will measure

  12. Geology of Mercury • Features of Mercury’s geology: • Dorsa • Impact basin’s and craters • Pit floor craters • Plains • Scarps • Volcanoes

  13. Features of Mercury - Dorsa Ridges Caused by faults in crust

  14. Features of Mercury - Craters Mercury is very heavily cratered. More so than the Moon. Predominant feature of Mercury Floors can be smooth plains

  15. Caloris Basin Largest crater in solar system 1,550 Km in diameter

  16. Weird Terrain Antipodal of Caloris Basin Where shock waves collided

  17. Features of Mercury – Pit Floor Craters Crater floor has collapsed Possible magma chamber under crater?

  18. Features of Mercury – Plains • Inter-crater plains are the oldest visible surface • occur in the regions between larger craters • Gently rolling hills • Smooth plains are widespread flat areas • resemble lunar maria • fill depressions

  19. Features of Mercury - Scarps Scarps are cliffs caused by the terrain moving vertically On Mercury, caused by crust shrinking as planet cooled.

  20. Features of Mercury - Volcanoes evidence of lava flows Cinder cone volcanoes Second most important feature-former

  21. Features of Mercury - Volcanoes

  22. Ice? On Mercury? It’s more likely than you think. Craters at pole may have water ice Bottom of crater is in permanent shadow Spotted with radar, need confirmation from MESSENGER

  23. Mercury’s Atmosphere • Very tenuous • about 2 trillionths of the atmospheric pressure on Earth • containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor • Solar wind gives Mercury a tail

  24. Exploring Mercury • Only two missions have visited Mercury: • Mariner 10 (1973) • MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) (2004)

  25. Mariner 10 • Last of the Mariner missions • Explored both Venus and Mercury • Could only map about 45% of Mercury • Same side was sunlit on each of the three flybys

  26. MESSENGER Can get better pictures of Mercury Has performed 3 flybys so far Will enter orbit of Mercury in March 2011

  27. Mercury - Summary Smallest planet 3:2 orbital resonance; most eccentric orbit Molten iron core Small but significant magnetic field Impact craters are biggest feature Ice in polar craters Very thin atmosphere

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