Well I can answer what the word beast suggests about the text.
I think it is suggests that they don't know much about the people of Mars, the life forms that lived there so they are frightened of them. They know that they are intelligent, or were, but also acknowledge how the planet is nearly impossible to sustain life with all of its water frozen.
Hope that helped, I don't know much about English class in highschool yet so I wasn't sure exactly how to answer the question.
This text relies on emotional bias.
For example, the portrayal of a bird drenched in oil shows the damaging effects of oil which only sides with one view.
The type of language used communicates a somber tone and creates a mood of desperation or sadness.