ASTR220
Collisions in Space
(Fall 2003; Richardson)
MIDTERM EXAMINATION
[11.00am-12.15pm, Thursday, 23rd October 2003]
Name:
Please sign the following honor pledge just before turning in your exam:
“I pledge on my honor that I have not given or received any unauthorized
assistance on this examination.”
Signed
Instructions for this examination:
1. Answer all questions.
2. No electronic calculators of any kind are to be used.
3. This is a closed-book exam: no notes are allowed.
4. Please write your answers directly on this exam paper in the space
after each question. Do not feel that you have to use all of the
available space.
5. If you need more space than provided, write the continuation of
your answer on a separate sheet of paper. Be sure to write your
name and the question number on every additional sheet you use.
Also staple the sheets to your exam when you hand everything in.
SECTION A (true/false questions – 1 point each)
For each question, circle the letter corresponding to the answer you think is best.
1. All planets spin in the same sense that they orbit the Sun.
a. True
b. False
2. An asteroid is typically more massive than a comet of the same shape and size.
a. True
b. False
3. Impact craters are circular because impactors tend to be spherical in shape.
a. True
b. False
4. Volcanoes can produce anomalously high iridium levels in rock layers.
a. True
b. False
5. The K-T crater was found by chance.
a. True
b. False
SECTION B (multiple-choice questions – 2 points each)
For each question, circle the letter corresponding to the best answer.
6. According to the scientific method, a theory
a. is a known law of the universe that is completely proven to be true.
b. can be proven if two people come up with the same results.
c. is rejected if new observations are made that are inconsistent with the theory.
d. need not be further tested by experimentation or observation once it seems
reasonable.
7. The most likely mechanism for the solar system’s formation is that the
a. Sun captured the planets as they drifted through space.
b. planets were spun out of the Sun as smaller gas clouds that subsequently
condensed.
c. solar system was once a galaxy, from which the Sun and planets are the
remnants.
d. Sun and planets condensed to their present form from a gas and dust cloud.
8. Which one of the following properties of the Moon is not explained by the Giant
Impact theory?
a. The Moon is depleted in iron compared to Earth.
b. The Moon has large impact basins called maria.
c. The Moon contains a higher proportion of refractory elements than Earth.
d. The Moon is at least 4.5 billion years old.
9. In the near-Earth environment there are about
a. one thousand asteroids larger than 1 km diameter and one million larger than
100 m diameter.
b. one hundred asteroids larger than 1 km diameter and one thousand larger than
100 m diameter.
c. one thousand asteroids smaller than 100 m diameter and one million smaller
than 1 km diameter.
d. one thousand asteroids larger than 10 km diameter and one million larger than
1 km diameter.
10. Which one of the following does not have the same energy as a 1 kg bowling ball
moving at 1 m/s?
a. A 250 g weight dropping at 2 m/s.
b. A 0.1 g bullet traveling at 100 m/s.
c. A 1,000 kg boulder moving at 1 cm/s.
d. A 0.001 g dust particle traveling at 1 km/s.
11. The SL9 event at Jupiter was scientifically important because
a. comets are rare in the solar system.
b. it was the first time a collision between two celestial bodies had been
witnessed.
c. Jupiter’s orbit was significantly perturbed by the collisions.
d. it was believed the collisions could strip away Jupiter’s atmosphere.
12. We believe that the Tunguska event was caused by
a. the explosion of a mini black hole.
b. the destruction of a UFO.
c. the mid-air explosion of a lump of anti-matter.
d. the mid-air breakup of an asteroid/comet fragment.
13. Which one of the following is the principal distinguishing feature between the
Cretaceous and Tertiary periods?
a. Only single-celled organisms existed during the Cretaceous whereas multicelled organisms appeared in the Tertiary.
b. Cretaceous rock layers contain dinosaur and mammal fossils whereas the
Tertiary layers contain only mammal fossils.
c. The Cretaceous has no crocodile fossils whereas the Tertiary does.
d. Ancient human tools have been found in the Cretaceous but not in the
Tertiary.
14. We believe the sequence of devasting events following the K-T impact was roughly
a. a huge blastwave followed by earthquakes and tsunamis, then global fires,
then global heating, and finally global cooling.
b. a huge blastwave followed by global fires, then global cooling, then
earthquakes and tsunamis, and finally global heating.
c. earthquakes and tsunamis followed by a huge blastwave, then global heating,
then global fires, and finally global cooling.
d. a huge blastwave followed by earthquakes and tsunamis, then global fires,
then global cooling, and finally global heating.
15. Which one of the following hazard mitigation strategies is most suitable for
preventing an imminent impact for which there is less than one year’s warning?
a. Installation of a mass driver on the object’s surface.
b. Using sunlight to vaporize surface layers from the object.
c. Detonating a nuclear device on or near the object.
d. Using a spacecraft “tug boat” to push the object out of the way.
SECTION C (short-answer questions – 5 points each)
Use the space provided to answer each question. Attach additional sheets if necessary.
16. In the space below sketch profiles of both a simple cater and a complex crater [2pts].
Be sure to label the important features [2pts]. Explain why an impactor that forms a
simple crater on Earth might form a complex crater if it hit the Moon instead [1pt].
17. Give three reasons why precisely dating extinction events based on the fossil record is
fraught with uncertainty [3pts]. Is it even possible to date extinctions precisely
without also conjecturing about the cause of the extinction? Explain [2pts].
18. What evidence is there that mass extinctions are both periodic and caused by impacts
[3pts]? Discuss one theory that might explain this if it were true [2pts].
19. In the last chapter of Night Comes to the Cretaceous, author Powell argues that
geology as a discipline has entered a “golden age.” Explain what he means and
comment on whether you agree [5pts].
20. Evidence is now strong that life on Earth has been greatly affected by random events
like impacts. However, the interval between impact events that could wipe out
civilization is long. Discuss whether putting into place a strategy for identifying and
deflecting potential impactors should be a high priority [5pts]. Be sure to back up
your argument either way with facts presented in class.