The Terrestrial Planets, Part I

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The Terrestrial Planets, Part I

• Mercury and Venus

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MERCURYThe Winged Messenger
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Physical Data

• Diameter 4,864 km (0.382 Dearth)
• Mass 3.33x1026 g (0.0558 Mearth)
• Density 5.50 g/cm3
• Rotation Period 58.65 days
• Tilt of Axis 0o
• Surface Temperature 700 K (day side) .
  100 K (dark
  side)

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Physical Data

• Orbital Semi-Major Axis 0.387 AU
• Perihelion Distance 0.308 AU
• Aphelion Distance 0.467 AU
• Orbital Period 87.97 days (0.241 years)
• Orbital Inclination 7.00o
• Orbital Eccentricity 0.206
• Surface Gravity 0.38 Earth gravity

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Physical Data

• Maximum Elongation 28o (aphelion)
• 18o
  (perihelion)
  . 23o
  (average)
• Satellites None
• Magnetic Field 1 strength of Earths

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Mercury Apparitions

• At western elongation, Mercury is visible in the
  morning before dawn (morning star).
• At eastern elongation, Mercury is visible in the
  evening after sunset (evening star).
• Mercury appears to change in size, and has phases
  like the Moon.

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Mercurys 32 Resonance

• Once thought to be synchronous
• Mercury rotates 3 times for every two orbits
• One Mercury day lasts two Mercurian years!

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Mercurys Interior

• Mercury is the most iron-rich planet in the solar
  system.
• Of all the planets, Mercury has the largest core
  relative to its overall volume (42, 16 for
  Earth)

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Mercurys Magnetic Field

• 1 Earths Magnetic Field

SUN
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Mercurys Surface

• Mercury appears very Moon-like

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Mercurys Surface

• Craters

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Mercurys Surface

• Lobate Scarps

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Mercurys Surface

• Caloris Basin - 1300 km diameter crater

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Mercurys Surface

• Weird (or Jumbled) Terrain
• Polar caps?

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Other Topics

• Precession of perihelion
• Radar measurements of Mercurys rotation

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VENUSThe Goddess of Love

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Physical Data

• Diameter 12,104 km (0.951 Dearth)
• Mass 4.87x1027 g (0.815 Mearth)
• Density 5.30 g/cm3
• Rotation Period 243 days
• Tilt of Axis 177.4o (retrograde)
• Suface Temperature 750 K

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Physical Data

• Orbital semi-major axis 0.723 AU
• Orbital period 224.70 days (0.615 years)
• Orbital inclination 3.39o
• Orbital Eccentricity 0.007
• Maximun Elongation 48o
• Surface Gravity 0.90 Earth gravity

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Physical Data

• Satellites None
• Magnetic Field No
• Surface Pressure 90 times Earths!

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Venus Apparitions

• At western elongation, Venus is visible in the
  morning before dawn (morning star).
• At eastern elongation, Venus is visible in the
  evening after sunset (evening star).
• Venus appears to change in size, and has phases
  like the Moon

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Clouds of Venus

• Clouds whiz aroud Venus at 300 km/hr.
• At this speed, a cloud can circle Venus in only
  four days.
• Clouds are composed of mostly sulfuric acid and
  water.

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The Atmosphere of Venus

• 96.5 Carbon Dioxide
• 3 Nitrogen
• Traces of Other Gases
• 0.019 Sulfur Dioxide
• 0.01 Water Vapor
• 0.007 Argon
• Hydrochloric acid, Hydroflouric acid
• Atmospheric Pressure 90x Earths

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Venus Atmosphere
105 km
75 km

• Clouds contain sulfuric acid and water
• Cloud tops appear yellow from sulfur dust
• Temperature reaches a maximum at the surface of
  about 750 K (900o F)

Top of Clouds
Upper Cloud Deck
60 km
Droplets of Sulfuric Acid Water
Altitude
Haze Layer
45 km
Lower Cloud Deck
Sulfuric Acid Water and Sulfur Crystals
Clouds T hin Out
30 km
Clear, Hot Atmosphere
15 km
0 km
0 K
200 K
400 K
600 K
800 K
Temperature
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Why is Venus So Hot?

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Venus Interior

• Core - 12 total volume of planet
• Molten core?
• Thin crust, with continent sized features.

Venus
CRUST ( silicates)
6052 km
3616 km
CORE ( iron-nickel )
MANTLE ( olivine )
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Soviet Venera Missions

• First Surface Photographs, 1970
• Photo from Venera 13

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The Magellan Mission

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Magellan Surface Imagery

• Suface Features
• Impact Craters
• Lava Flows
• Volcanic Calderas
• Volcanoes
• Peculiar to Venus
• Coronae, Pancake . Domes, Ticks,
  Graph Paper Regions

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Venus Surface

• Graph Paper Regions

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Venus Surface

• The Tick

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Venus Surface

• Coronae

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Venus Surface

• Pancake Domes