Physics 320: Astronomy and Astrophysics

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Physics 320 Astronomy and Astrophysics Lecture
XII

• Carsten Denker
• Physics Department
• Center for SolarTerrestrial Research

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Problem 18.1
Mass MMercury Radius RMercury
Moon 0.223 0.712
Io 0.270 0.744
Europa 0.148 0.643
Ganymede 0.452 1.078
Callisto 0.327 0.984
Titan 0.409 1.055
Triton 0.065 0.555
Pluto 0.040 0.460
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Problem 18.5
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Problem 18.7
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The Terrestrial Planets

• Mercury
• Venus
• Earth
• The Moon
• Mars

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Mercury

• The four terrestrial planets are small, rocky,
  and rotate slowly ? cf. moons
• _at_ 0.34 AU Keplers laws break down ? Einsteins
  theory of special relativity
• Eccentricity of orbit e 0.206
• Rotation period T 58.65 days ? Doppler effect
• Orbital period 87.97 days 3/2 T

• Mariner 10 found strong resemblance to the moon
• Proximity to Sun and size ? very tenuous
  atmosphere

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Mercury and Caloris Basin
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3-to-2 Spin-Orbit Coupling

• Tidal Evolution
• Strongest tidal force at perihelion
• Energy dissipation due to friction

• Circularization of Mercurys orbit
• 3-to-2 spin-orbit coupling become instable
• 1-to-1 resonance of synchronous rotation

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Venus

• Earths sister planet
• Mass 0.82 MEarth
• Radius 0.95 REarth
• Retrograde atmospheric circulation (100 m/s at
  cloud tops near equator)
• Hadley cells (y-shaped cloud pattern at
  equator)
• Retrograde rotation of the planet
• Sidereal rotation period 243 days
• Orbital period 224.7 days

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Phases
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Atmosphere

• 96.4 carbon dioxide CO2
• 3.4 molecular nitrogen N2
• Traces of sulfur dioxide SO2, water H2O, and
  clouds of sulfuric acid
• Temperature 740 K and pressure 90 atm at base of
  atmosphere
• Optically thick in the infrared
• Volcanism and/or material delivered by comets and
  meteorites

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Greenhouse Effect
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Surface
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Earth

• Condensation of water forms oceans early in the
  history of Earth
• No conversion of liquid water into vapor!
• Carbon dioxide dissolved in water or chemically
  bound, e.g., carbonate rocks
• 72 molecular nitrogen N2
• 21 molecular oxygen O2

• 1 water H2O
• Traces of argon AR, carbon dioxide CO2,
• Photosynthesis CO2 ? organic materials O2
• Increase of greenhouse gases
• Annual oscillation of CO2 due to vegetation
  cycles
• Rainforest
• Ozone O3 layer

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Structure and Atmosphere
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Gravity Map of Earth
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Methane Earth
Recent evidence holds that methane (CH4) is
second only to carbon dioxide (CO2)
in creating a warming greenhouse effect but
is easier to control. Atmospheric
methane has doubled over the
past 200 years, and its smothering potency is
over 20 times that of CO2.
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Seismic Activity
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Moon

• Moon quakes due to tidal strain (magnitude 1 on
  Richter scale)
• The Moons ringing after being struck by
  meteorites
• Craters and maria seas
• Crust is thinner on near side

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Structure and Formation
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Radioactive Dating
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Mars

• Canali Giovanni Virginio Schiaparelli (1835
  1910)
• Lowell (1855 1916) observatory, Flagstaff, AZ
• Intelligent life on Mars? LGM? (H. G. Wells War
  of the Worlds broadcasted on October 30th, 1938)
• Surface temperature ?140 C to 20 C
• 95 carbon dioxide CO2

• 2.7 molecular nitrogen N2
• Atmospheric pressure 0.001 atm
• Water in layers of permafrost or frozen in polar
  ice caps
• Polar caps predominantly dry ice frozen carbon
  dioxide
• General relativity required to explain tilt of
  Mars spin axis
• No large Moon!

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Atmosphere and Volcanism
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Deimos and Phobos
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Ancient Streams and Dunes
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(Happy) Faces and Hearts
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Homework Class Project

• Continue improving the PPT presentation.
• Use the abstract from the previous assignment as
  a starting point for a PowerPoint presentation.
• The PPT presentation should have between 5 and 10
  slides.
• Bring a print-out of the draft version to the
  next class as a discussion template for group
  work
• Homework is due Wednesday December 3rd, 2003! It
  would be good to have your final versions by then
  in order to have the final grades on December
  10th, 2003.
• Exhibition name competition (Final)!

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Homework

• No homework!!!
• The Final Exam will be due on December 3rd, 2003
  at the beginning of the lecture.
• Please feel free to contact me with any questions
  concerning the final exam.