Astro 120: Fall 2003
Exam 2 Essay Question

PART II: ESSAY (20 points):

Answer the question on this sheet front and (if needed) back only

Name: ____________________________ Section Number: __________________

Throughout this part of the course, we have looked at the planets of our Solar System, and the small bodies that attend them (satellites and rings). Though they display a huge range of properties, there are some important similarities between features found on their surfaces, and in their atmospheres. With this in mind, answer each of these two questions, in a brief but well reasoned paragraph using proper English grammar. You may use diagrams to illustrate your point(s), in addition to the words.

1. (10 pts) Impacts of bodies larger than 30 meters in diameter produce craters on the surfaces that they hit. We see a large number of craters on the surfaces of most satellites of the planets, and on most of the terrestrial planets. However, some solid bodies show few if any craters. One of them is the Earth. Explain why the Earth, and one other body in the solar system that has a solid surface, show few if any impact craters. In your answer be sure to address the following points with specifics.
   1. Is the lack of craters connected to a lack of objects that can crash into the bodies?
   2. If so, why are there so few objects? If not, where are the craters?

2. (10 pts) In all planets that have atmospheres, we see clouds. For example, the clouds of Venus appear greenish-white; Earth clouds are white, Jupiter has white, brown, and even red clouds, Neptune has a vivid blue-green color. Pick any two planets with different colored clouds (you don't need to restrict yourself to the ones mentioned above) and explain why the clouds look different on each planet. As a hint, for each planet be sure to mention the main constituent of its atmosphere and that of the clouds we see.