ASTR220 Midterm Review Sheet
Suggestions
1. Review the textbook chapters. You should be able to summarize the main points
of each chapter in a sentence or two.
2. Go over your homework and the in-class quiz. Be sure you understand any
questions you got wrong.
3. Go over the online class notes. You are responsible for anything covered in class.
Concepts, Ideas, and Facts You Should Know
1. The basic constituents of the solar system: the Sun, planets, asteroids, comets.
2. The formation of the solar system and the facts theories need to explain.
3. The collapsing cloud model and the role of bombardment in the solar system.
4. The diversity of planetary surfaces and the processes that affect them.
5. The physics of collisions and crater formation: kinetic energy vs. momentum.
6. Simple and complex craters; signatures of impact.
7. The Moon: properties, tidal effects, and formation theories.
8. Details about asteroids and comets: what are they, where do they come from?
9. SL9 and Tunguska: what happened and what have we learned?
10. Geological ages, life on Earth, and mass extinctions.
11. The K-T boundary: facts to be explained and why impact works best.
12. Radiometric dating: how does it work?
13. Other mass extinctions and the Nemesis Theory.
14. Classes of impact, assessment of risk, and hazard mitigation strategies.
Questions You Should Think About
1. How can we test theories of the formation of the solar system?
2. Why is each planet in the solar system so different?
3. Why are virtually all impact craters circular?
4. What can the Moon tell us about the early history of the solar system?
5. What would it take to deflect or blow up a hazardous asteroid or comet?
6. How are geological ages established?
7. What affects whether an extinction event seems abrupt or gradual?
8. What was the Earth like during the millennium following the K-T impact?
9. What facts (if any) does the Alvarez theory currently not explain very well?
10. Why is the Shriva Hypothesis so uncertain?
11. Which class of impact is the most dangerous to modern civilization?
12. Is it worth worrying about the possibility of a future impact? Explain.