One most eloquent writings that I have ever read comes from page 8 of Carl Sagan’s 1994 book, Pale Blue Dot:

Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.

The passage refers to a photograph taken of Earth by Voyager 1 at a distance of about 4 billion miles.

The words themselves are carefully chosen to create a certain frame of mind in the audience by evoking different emotions. Sagan also uses figures to further his intended affect. Primarily, he uses repetition and antithesis. Repetition, chiefly in the form of anaphora, allows Sagan to place strong emphasis on his particular points and make those points memorable. Through antithesis, Sagan engages his readers and challenges them to actively think while reading. The finely chosen words and figures combine to make an emotionally-moving passage. This passage is then combined with the powerful photo to which it refers to create a true rhetorical masterpiece.

By the end of the passage, the audience is emotionally open and here is where Sagan places his suggestion to be kind and take care of the Earth. This is an effective structure because by creating an emotional connection with his audience Sagan improves the probability of them accepting his suggestion. It is important to note that he uses a suggestion and not a command which would disrupt the emotional nature of the passage. But Sagan does not rely solely on pathos; indeed, there is a certain logic to his writing. Additionally, Sagan has considerable credibility because he is was one of the preeminent astronomers of his time.