1. Lecture 12: Planetary Geology
There are two major types of planets
Terrestrial planets versus Jovian-sized planets
Will focus on terrestrial planets
Overview of Common Characteristics of the
Terrestrial Planets
Have relatively high surface temperatures
- Located close to the sun
(2) Have high densities
(3) Are relative small compared with Jovian-sized planets
(4) Have thin or no atmospheres compared with Jovian planets
(5) Have few or no moons compared …

2. The Terrestrial Planets

3. Planet #1 - Mercury: Craters

4. Some Characteristics of Mercury
Planet #1
No Moons
Geologically dead
- Probably for the last 3 b.y.
No significant atmosphere or hydrosphere
Heavily cratered
- Why?

5. Some Venus Facts Planet #2 No Moons Geologically active
- Has both volcanoes and mountain building
- Has “Venus”quakes and active fault zones

6. Mountains on Venus

7. FAULT VALLEYS ON VENUS

8. Volcanoes on Venus

9. Venus: Cloud Deck

10. SOME FACTS ABOUT VENUS’ ATMOSPHERE
Sulfuric acids rains in the upper atmosphere
Surface temperature of 450 C
Atmospheric pressure at the surface of 90 bars
Atmosphere consists of mainly carbon dioxide (CO %)

11. The Earth: Planet #3
We do have a Moon

12. Brief history of the Moon:
Formed 4.5 b.y. ago
- When a Mars-sized body impacted the earth and ejected
material into earth’s orbit
At 4.5 b.y. the original lunar crust formed (The Lunar Highlands)
- Igneous rock
Between 4.1 to 4.5 b.y. ago this crust was heavily bombarded by
Asteroids
From 3.1 to 4.1 b.y. massive volcanic activity took place forming the
lunar maria (Flatlands or face in the man on the moon)
At 3.1 b.y. ago the moon solidified and essentially became geologic
dead

13. In the Beginning: Massive Collision

14. How do we know this much about the moon?
Moon rocks

15. The Red Planet: Mars

16. Some Characteristics of Mars
Planet #4
Two Small Moons (really just asteroids)
Thin atmosphere (not breathable)
No oceans or water on the surface
- But below the surface???

17. Deimos: One of Mars’ Tiny Moons

18. MARS: MONS OLYMPUS

19. Planet #4 - Mars
What can you infer about geologic activity on Mars?
- Any active volcanoes today on Mars?
- No
- But, in the not so distant geologic past there
were volcanoes?
- About 1 b.y. ago

20. Asteriod:
Solidified in 100 m.y.
Activity Complete by 4.5 b.y. ago
Mass <0.001 Earth
Moon:
Solidified in 1.5 b.y.
Activity Complete by 3.1 b.y. ago
Mass = Earth
Mars:
Solidified in 3 to 4 b.y.
Activity Complete by ≈ 1 b.y. ago
Mass = 0.11 Earth

21. GENERAL PRINCIPLE OF TERRESTRIAL PLANETARY
DEVELOPMENT
The bigger the planetary body the longer it takes to cool.
Geological activity (volcanoes, mountain building) will occur
over a greater duration when planetary bodies are larger!
YOU MUST be able to compare at the duration of geological
activity for bodies such as asteroids, the moon, Mars, and the
earth

22. What about the prospects for life
on the Martian surface today?

23. Have pieces of Mars on Earth
The Martian meteorites

24. The fossilized Martians?????

25. Overview of Common Characteristics of the
Jovian Planets (Planets 5 to 8)
Have relatively low surface temperatures
- Located far from the sun
(2) Have low densities
Are large in their diameter compared with terrestrial-
sized planets
Have extremely thick atmospheres
- Essentially are large gas balls
Have many moons compared with terrestrial sized planets
- Can be thought of as mini-solar systems

26. Jupiter (Planet #5): The largest planet in the solar system

27. Icy Balls: Ganymede a typical moon around a Jovian planet
Not like the rocky moon that we have around the earth!

28. And what of Pluto (Planet #9 ?)