1. The Terrestrial Planets, Part I
Mercury and Venus

2. MERCURY The Winged Messenger

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

4. Physical Data Orbital Semi-Major Axis: 0.387 AU
Perihelion Distance: AU
Aphelion Distance: AU
Orbital Period : days (0.241 years)
Orbital Inclination: 7.00o
Orbital Eccentricity: 0.206
Surface Gravity: 0.38 Earth gravity

5. Physical Data Maximum Elongation: 28o (aphelion)
18o (perihelion) o (average)
Satellites: None
Magnetic Field: 1% strength of Earth’s

6. 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.

7. Mercury’s 3:2 Resonance Once thought to be synchronous
Mercury rotates 3 times for every two orbits
One Mercury “day” lasts two Mercurian years!

8. Mercury’s 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)

9. Mercury’s Magnetic Field
1% Earth’s Magnetic Field
SUN

10. Mercury’s Surface
Mercury appears very Moon-like

11. Mercury’s Surface
Craters

12. Mercury’s Surface
Lobate Scarps

13. Mercury’s Surface
Caloris Basin km diameter crater

14. Mercury’s Surface
“Weird” (or Jumbled) Terrain
Polar caps?

15. Other Topics: Precession of perihelion
Radar measurements of Mercury’s rotation

16. VENUS The Goddess of Love

17. 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

18. Physical Data Orbital semi-major axis: 0.723 AU
Orbital period: days (0.615 years)
Orbital inclination: 3.39o
Orbital Eccentricity: 0.007
Maximun Elongation: 48o
Surface Gravity: 0.90 Earth gravity

19. Physical Data Satellites: None Magnetic Field: No
Surface Pressure: 90 times Earth’s!

20. 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

21. 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.

22. 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 Earth’s

23. Venus’ Atmosphere Clouds contain sulfuric acid and water
105 km
Venus’ Atmosphere
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)
75 km
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

24. Why is Venus So Hot?

25. 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 )

26. Soviet Venera Missions
First Surface Photographs, 1970
Photo from Venera 13

27. The Magellan Mission

28. Magellan Surface Imagery
Suface Features:
Impact Craters
Lava Flows
Volcanic Calderas
Volcanoes
Peculiar to Venus:
Coronae, Pancake Domes, Ticks, Graph Paper Regions

29. Venus’ Surface
Graph Paper Regions

30. Venus’ Surface
“The Tick”

31. Venus’ Surface
Coronae

32. Venus’ Surface
Pancake Domes