It gives examples on how Jack and the boys personalities, characteristics, etc. are.
Hope this helps.
The setting is where the story takes place.
Answer: I'm not going to write your whole essay for you, but some good reasons to use would be: A change in atmosphere, they can experience what life is like on a different planet, they can get a chance to learn more about mars or anything else about space, and they can compare and contrast how different mars is from earth along with make new memories on a different planet.
