### ASTR 220 - Collisions in Space

#### Homework 2 (12 points) Due Thursday October 7 at the beginning of class

1. Demise of the Dinosaurs:
Summarize the theory that an asteroid impact triggered a global catastrophe roughly 65 million years ago. Describe the observations which support this hypothesis.

2. Formation of the Moon:
Explain why a new theory for the formation of the Moon was necessary after the Apollo landings. (Discuss the observations made and describe the theory.)

3. Kinetic Energy and Meteor Crater:
It is estimated that the body (asteroid) whose impact formed Meteor Crater, AZ was about 60 meters in diameter and its composition was most similar to an iron meteorite. Its velocity is estimated at 20 km/s. This impact formed a crater 1.2 km (0.75 miles) in diameter. For each of a-c, first use the kinetic energy equation (E = M V2/2) to predict how the energy of motion of the impactor would be affected by the given change (i.e. increase/decrease by a factor of X -- find X). More energy means a bigger crater. (Only simple calculations are necessary; use the table on Handout #6 and the "Working with Equations" link on the web page if you need help.) You can check your answer by modeling each impact on the "Collisions with Planets" link from the class web page. Write down the amount of energy released in each impact, and the diameter of the resulting crater.
• a) what if the velocity was 60 km/s (instead of 20 km/s)?
• b) what if the asteroid was 120 meters in diameter (instead of 60 meters)?
• c) what if it was a comet nucleus of density 0.75 grams per cubic cm (rather than an iron asteroid of density 7.5 grams per cubic cm)?

4. Comet crash or What?
In July 1994, Professor Fink was studying Jupiter. Unfortunately, he was too busy with his own work to have heard that comet Shoemaker-Levy 9 had been discovered prior to impacting Jupiter. When he takes the first of the pictures of Jupiter below on 25 July 1994, he is puzzled by the unusual bright spots. After some thought, Fink hypothesizes that these are Jupiter's response to solar activity which continued for several months. Do the subsequent pictures support or contradict Fink's hypothesis? Why?