1. Thought Question What does the solar system look like as a whole?
Why does the solar system look the way it does?
Can we explain how the solar system first formed?

2. In studying the solar system…
We look for patterns amongst the planets.
We look for characteristics that the planets share.
We look characteristics that they do NOT share.
Can we explain these similarities and differences?

3. Rocky surface, iron, nickel interiors
Planet Comparisons
Property Terrestrial Planets Jovian Planets
Distance from Sun
Close
Far
Mass
Small
Large
Size
Composition
Rocky surface, iron, nickel interiors
Gaseous (H & He)
Moons
Few
Many
Rings
None
Yes
Density
High
Low

4. Planet Comparisons Distance from Sun Mass Size Composition Moons Rings
Property Terrestrial Planets Jovian Planets
Distance from Sun
Mass
Size
Composition
Moons
Rings
Density

5. Terrestrial Planet Comparisons
Property Similarities Differences
atmospheres
composition of atmosphere
composition of surface
structures
cratering
temperatures

6. Jovian Planet Comparisons
Property Similarities Differences
composition of atmosphere
atmospheric storms and winds
rings
moons
Appearance of planet

7. How are the planets classified?
Terrestrial: Mercury, Venus, Earth, Mars
Jovian: Jupiter, Saturn, Uranus, Neptune

12. The Origin of the Solar System should explain…
1. Motion of the planets
Planets orbit in the same direction...
...in nearly the same plane...
...in nearly circular orbits.
Most planets rotate in the same direction.
Most moons orbit in the same direction.
2. Categorizing Planets
Planets are either rocky or gaseous.

13. The Origin of the Solar System should explain…
3. Asteroids and Comets
Most asteroids are found between Mars and Jupiter.
Most comets have highly elliptical orbits.
4. Age of solar system
Common age of rock samples, asteroids, meteorites (4.5 billion years).
Common cratering age of ~3.8 billion years
5. Exceptions to the Rules
What about Pluto’s elliptical orbit and composition?
What about the odd rotation of Venus and Uranus?

14. Formation of the Solar System
We look for a simple, logical, physical explanation for the similarities and differences we see in the planets.
We look for a framework that fits with observations—A THEORY!
The solar system formed from a cloud of gas and dust in a process known as accretion.

15. We see evidence of accretion disk around other stars.
Q: What is another reason we believe the solar system formed this way?
A: ….because we see it happening elsewhere!
We see evidence of accretion disk around other stars.
For example, this accretion disk around the star
b Pictoris.