1. EARLY HISTORY OF THE TERRESTRIAL PLANETS
Grotzinger • Jordan
Understanding Earth
Sixth Edition
Chapter 9:
EARLY HISTORY OF THE TERRESTRIAL PLANETS
© 2011 by W. H. Freeman and Company

2. Early History of the Terrestrial Planets
Chapter 9:
Early History of the Terrestrial Planets

3. About Terrestrial Planets
The solar system and its planets formed around the Sun.
The planets differentiated into layered bodies.
The geologic processes that formed Mercury, Venus, Earth, Moon, and Mars are similar in many ways.

4. Lecture Outline Origin of the solar system
2. Early Earth: forming a layered planet
3. Diversity of the planets
4. The age and complexion of planetary surfaces
5. Mars rocks!
6. Exploring the solar system and beyond

5. 1. Origin of the Solar System
● The nebular hypothesis
● the sun forms
● the planets form
● planetesimals
● inner planets
● outer planets

10. ● Small bodies of the solar system ● asteroids ● meteorities
1. Origin of the Solar System
● Small bodies of the solar system
● asteroids
● meteorities

11. The structure of the solar system
1. Origin of the Solar System
The structure of the solar system

12. Thought questions for this chapter
If a giant impact such as the one that formed the Moon had occurred after life had arisen on Earth, what would have been the consequences?

13. ● Differentiation – transformation into a layered planet
2. Early Earth: Forming
a Layered Planet
● Differentiation – transformation
into a layered planet
● Earth heats up and melts
● the magma ocean
● impact formation of the Moon

15. ● Differentiation – transformation into a layered planet
2. Early Earth: Forming
a Layered Planet
● Differentiation – transformation
into a layered planet
● Earth’s core, mantle, and crust form
● Earth’s oceans and
atmosphere form

18. Thought questions for this chapter
Knowing how the Moon formed, what might you expect as a result if you were told that a large meteorite had collided with a planet twice its size? What could be the effect of this collision on the interior compositions of this planet? How would the result of the impact differ if the meteorite were significantly smaller than the planet?
If you were an astronaut landing on an unexplored planet, how would you decide whether the planet was differentiated and whether it was tectonically alive?

19. ● Mercury – very hot, many craters, thin helium atmosphere
3. Diversity of the Planets
● Mercury – very hot, many craters, thin helium atmosphere
● Venus – very hot, covered by lava flows, thick acid atmosphere
● Earth – usually pretty nice, lots of water, nitrogen-oxygen atmosphere

21. 3. Diversity of the Planets
● Earth’s Moon – cold, many craters (shows evidence of periods of heavy bombardment by asteroids), no atmosphere
● Mars – cold, many craters and dry river valleys, thin carbon- dioxide atmosphere

22. Lunar highlands (light) and maria (dark)

25. ● Outer planets – gaseous bodies made mainly of hydrogen and helium
3. Diversity of the Planets
● Outer planets – gaseous bodies made mainly of hydrogen and helium
● Jupiter
● Saturn
● Uranus
● Neptune

26. 3. Diversity of the Planets
● Pluto – frozen gas, ice, and rock body in an unusual orbit; a dwarf planet of the outer solar system
● Dwarf planets – small frozen planetary bodies beyond the orbit of Neptune, source region for periodic comets

27. ● Planetary time scales ● Moon
4. Age and Complexion
of Planetary Surfaces
● Planetary time scales
● Moon
● formation of highlands (4400 to 4000 Ma)
● formation of lunar maria
(4000 to 3200 Ma)

28. ● Planetary time scales ● Mercury ● impacts and lava flows
4. Age and Complexion
of Planetary Surfaces
● Planetary time scales
● Mercury
● impacts and lava flows
● cooling and contraction

29. Mercury

30. Fault scarp produced by cooling and contraction of Mercury

31. ● Planetary time scales ● Venus ● flake tectonics
4. Age and Complexion
of Planetary Surfaces
● Planetary time scales
● Venus
● flake tectonics
● extensive lava flows
(oldest surface 500 Ma)

32. Topography of Venus

33. Coronae on Venus

34. Volcanic mountain on Venus

35. Tectonics of Earth and Venus

36. ● Planetary time scales ● Mars
4. Age and Complexion
of Planetary Surfaces
● Planetary time scales
● Mars
● formation of ancient cratered terrains ( to 3800 Ma)
● period of water flows
(3900 to 3500 Ma)

38. Part of Vallis Marineris, Mars

39. Olympus Mons volcano, Mars

40. ● Planetary time scales ● Earth ● core-mantle separation (4400 Ma)
4. Age and Complexion
of Planetary Surfaces
● Planetary time scales
● Earth
● core-mantle separation (4400 Ma)
● liquid oceans form
(4000 Ma)
● end of heavy bombardment (3900 Ma)

42. ● Impact craters on Earth ● found on continents
4. Age and Complexion
of Planetary Surfaces
● Impact craters on Earth
● found on continents
● rare structures formed by meteorite or asteroid impact

43. Location of impact craters on Earth

47. ● Missions to Mars ● Mariner (1965 and 1971) 5. Mars Rocks!
● Viking (19761980)
● Pathfinder (1997)
● Mars Global Surveyor (19962006) and Mars Odyssey (2001date)
● Mars Reconnaissance Orbiter (2005date)
● Mars Exploration Rovers (2004date)
● Mars Express (20052006)

48. Viking: dry river channel networks

49. Mars Global Surveyor: dry river channel
networks

50. Mars Exploration Rover (Spirit) landing site: floor of Gusev crater

51. Mars Exploration Rover (Opportunity) landing site: plains with hematite

52. Mars Exploration Rover (Opportunity) photo: sulfate-rich sedimentary rock

53. Mars Exploration Rover (Opportunity) photo: stratigraphy in wall of endurance crater

54. Thought questions for this chapter
During a dust storm on Mars, sediments fill the atmosphere with dust. But Mars has an atmosphere much thinner than that of Earth. To move sand, would the wind have to blow faster on Mars to compensate for this difference?
Many scientists think that water is present on Mars. Today it is frozen, but 4 billion years ago, it may have been liquid. What happened? Describe all the possible mechanisms for this change. What evidence would you search for to help decide among these possibilities?

55. 6. Exploring the Solar System
and Beyond
● Recent space missions
● Cassini mission to Saturn with
Huygens landing on Titan
● Deep Impact – mission to comet Tempel I
● Study of other solar systems: the
search for exoplanets

56. Cassini view of Saturn in 2004

57. Huygens lander view of methane surface of Titan

58. Deep Impact strikes comet Tempel I

59. Thought questions for this chapter
How does the discovery of planets orbiting other stars contribute to the debate about the possibility of life elsewhere in the cosmos? What are the scientific and philosophical implications of the existence of life on the planets of other stars?
What are the advantages and disadvantages of living on a differentiated planet? On a geologically active planet?

60. Key terms and concepts Dwarf planet Exoplanet Flake tectonics
Asteroid
Dwarf planet
Exoplanet
Flake tectonics
Heavy bombardment
Meteorite
Nebular hypothesis
Planetesimal
Solar nebula
Spectrum