VENUS

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VENUS
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Bulk Properties

• Radius 0.95 Earth radii
• Mass 0.82 Earth masses
• Density 5.24 g/cm3
• Semi-Major Axis 0.72 AU (0.72 0.73)
• Orbital Period 225 days
• Rotational Period 243 days
• Retrograde Rotation
• Axial Tilt 177.4 degrees
• Mean surface Temp 730 K

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Long Distance Observation

• Venus is visible just after sundown or just
  before sunrise
• Never more than 47 degrees from the Sun
• Third brightest object in the sky
• 10x brighter than Sirius (a CMa)
• Telescopic views show a white-yellow disk
• UV views show cloud circulation
• Radio images show the surface

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The Surface of Venus

• Nearly all info about Venuss surface is from
  radargraphs
• Most of the planet is relatively smooth,
  resembling rolling plains
• Two continent-sized highlands (Ishtar and
  Aphrodite) contain mountains comparable to those
  on Earth
• Make up just 8 of the surface

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The Continents of Venus

• Ishtar Terra
• Lies in the Southern high latitudes (top)
• About the size of Australia
• Dominated by a giant plateau ringed by mountains,
  including the highest on the planet (Maxwell
  Mons)
• Aphrodite Terra
• Located on the equator
• About the size of Africa

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Volcanoes

• Lava domes are numerous
• There are many large shield volcanoes
• No evidence of tectonic plates, so must be over
  hotspots
• No eruption has been observed but there is
  circumstantial evidence that the volcanoes remain
  active
• Fluctuations in the SO2 content of the atmosphere
• Radio energy bursts (lightning)

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The Atmosphere of Venus

• About 90x more massive than Earths atmosphere
  and extends further from the surface
• 96.5 CO2, 3.5 N2
• Trace amounts of other gases
• Highly reflective clouds cover the entire surface
  (albedo around 0.7)
• Made of condensed sulfuric acid

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Runaway Greenhouse Effect

• The large quantities of carbon dioxide trap the
  IR radiated from the surface
• Nearly 99 effective in trapping heat
• Temperature is nearly the same at poles as the
  equator, and on the daytime/nighttime sides

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Venuss Interior

• Almost certainly similar to Earths
• Rocky crust
• Molten mantle
• Partially molten Iron core
• Why no tectonics?
• No one really knows
• Venus has absolutely no magnetic field
• Most likely due to its extremely slow rotation

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Venus Exploration

• Venera
• Russian for Venus
• 16 probes launched from 1961 to 1984
• 1,2,3 lost communication before arrival
• 4 was first spacecraft to enter another
  atmosphere and return data
• 7 was the first to land and return data

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Venus Exploration

• Mariner
• NASA program for planetary observation
• Mariner 1 failed
• Mariner 2 was the first spacecraft to fly-by
  another planet (Venus)
• 3 and 4 went to Mars (3 didnt make it)
• 5 to Venus
• 6,7,8,9 to Mars (8 failed)
• 10 went to Mercury via Venus

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Venus Exploration

• Magellan
• Arrived in orbit in 1990
• High resolution mapping of Venuss surface
• Radar mapping
• Entered the atmosphere in 1994