1. Xi Zhang E&MS A261 <xiz@ucsc.edu>
Planetary Discovery
in the era of Spacecraft Exploration
Xi Zhang
E&MS A261
TA: Szilard Gyalay

2. Homework #3 is due this Friday.
Homework #4 is online now.
Mid-term next Friday (11/03) at 10:40 am.

3. Outline of this week Overview of solar system
Formation of star and planetary system
Terrestrial Planets: surface and interior
Chap. 7, 8, 9

4. How do robotic spacecraft work?
Flyby: flies by another world only once
Orbiter: goes into orbit around another world
Probe/Lander: lands on surface
Sample return mission: returns a sample of another world's surface to Earth

5. Earth, as viewed by the Voyager spacecraft

6. Today’s Outline Overview of solar system
Formation of star and planetary system

7. Overview of Solar System

8. Main Features
There are eight major planets with nearly circular orbits.
Planets all orbit in same direction and nearly in same plane.
Dwarf planets are smaller than the major planets and some have quite elliptical orbits.

9. Motion of Large Bodies
All large bodies in the solar system orbit in the same direction and in nearly the same plane.
Most also rotate in that direction (e.g. Venus does not).

10. Two Major Planet Types
Terrestrial planets are rocky, relatively small, and close to the Sun.
Jovian planets are gaseous, larger, and farther from the Sun.

11. Swarms of Smaller Bodies
Many rocky asteroids and icy comets populate the solar system.

12. Notable Exceptions
Several exceptions to the normal patterns need to be explained.

13. Tilting and Self-Rotation

14. Sun and planets to scale (size, not orbital distance)
Solar system model to scale:

15. Quiz How does the Earth–Sun distance compare with the Sun's radius?
It's about 10 times larger.
It's about 50 times larger.
It's about 200 times larger.
It's about 1000 times larger.

16. Quiz How does the Earth–Sun distance compare with the Sun's radius?
It's about 10 times larger.
It's about 50 times larger.
It's about 200 times larger.
It's about 1000 times larger.

17. Sun Over 99.9% of solar system's mass Made mostly of H/He gas (plasma)
These slides follow the planetary tour pages in Chapter 7.
Over 99.9% of solar system's mass
Made mostly of H/He gas (plasma)
Converts 4 million tons of mass into energy each second

18. Mercury Made of metal and rock; large iron core
Desolate, cratered; long, tall, steep cliffs
Very hot, very cold: 425 celsius degree (day), –170 celsius degree (night)

19. Venus Nearly identical in size to Earth; surface hidden by clouds
Hellish conditions due to an extreme greenhouse effect
Even hotter than Mercury: 470 celsius degree, day and night

20. Earth
Earth and moon with sizes shown to scale
An oasis of life
The only surface liquid water in the solar system
A surprisingly large moon

21. Mars Looks almost Earth-like, but don't go without a spacesuit!
Giant volcanoes, a huge canyon, polar caps, more
Water flowed in distant past; could there have been life?

22. Mars
Curiosity rover landed in August 2012.

23. Jupiter Much farther from Sun than inner planets
Mostly H/He; no solid surface
300 times more massive than Earth
Many moons, rings

24. Jupiter’s moons
Jupiter's moons can be as interesting as planets themselves, especially Jupiter's four Galilean moons.
Io: active volcanoes all over
Europa: possible subsurface ocean
Ganymede: largest moon in solar system
Callisto: a large, cratered "ice ball"

25. Saturn Giant and gaseous like Jupiter Spectacular rings
Many moons, including Enceladus, and cloudy (hazy) Titan

26. Saturn’s rings
Rings are NOT solid; they are made of countless small chunks of ice and rock, each orbiting like a tiny moon.

27. Saturn’s moon Titan
Cassini spacecraft arrived July 2004 (launched in 1997).
The figure on the right shows the Huygens probe separated from the main spacecraft on its descent to Titan.

28. Uranus Smaller than Jupiter/Saturn; much larger than Earth
Made of H/He gas and hydrogen compounds (H2O, NH3, CH4)
Extreme axis tilt
Moons and rings

29. Neptune Similar to Uranus (except for axis tilt)
Many moons (including Triton)

30. Neptune-size exoplanets are common from Kepler mission

31. Dwarf Planets: Pluto, Eris, and more
Much smaller than major planets
Icy, comet-like composition
Pluto's main moon (Charon) is of similar size

32. Table 7.1
This important summary table may be worth some time in class to make sure students understand how to read it…

33. What properties of our solar system must a formation theory explain?
Patterns of motion of the large bodies
Orbit in same direction and plane
Existence of two types of planets
Terrestrial and jovian
Existence of smaller bodies
Asteroids and comets
Notable exceptions to usual patterns
Rotation of Uranus, Earth's Moon, etc.

34. Today’s Outline Overview of solar system
Formation of star and planetary system

35. Origin of the Universe: The Big Bang
The Big Bang produces Hydrogen and Helium