Astronomy discussion board---250 words

Discussion Topic:

Compare comets and asteroids. What are similarities and differences between the two? Take into account structure, appearance, orbits and forces acting upon them.

Writing Your Response:

1. Students need to use proper grammar and writing techniques. Responses should be complete, well thought out, and presented in a logical manner. 
2. A minimum of one paragraph is required for this posting. 
3. You are not required to support your post with references, but you are encouraged to include images, graphics, links to videos, and so on to create a more dynamic submission.