As I see it, we Earthlings are (some of) the only conscious beings in the universe; thus, I believe that it is we who bear witness to the beauty and terror of the universe, and it is we who create all meaning which is to be found in it. Because the concept of meaning is subjective and the end of a unanimous subjective congress tends to be one brain (i.e, one mind), then it up to each one of us individuals to create meaning. Unfortunately, because meaning is subjective, no two individuals may ever wholly agree on the level of meaning of a given concept like two scientists agree on a theory. Thus, what matters is, I believe, purely up to you. Practice two things: 1) trusting that what you believe to be important IS important and 2) finding more and more people who value the same things you do, with the same level of enthusiasm. Confidence and support are the two keys to a life that will matter, believe me! Also, look up existentialism; there's a whole community out there of people like you and me who suffer depression by this very question. I also recommend a book by the
name of "The Van Gogh Blues;" I hope it helps you cope with the problem of meaning like it helped me!
And to answer your questions: Yes, you, I, and the earth matter. Just ask your friends and family, and the reply will be, "Of COURSE you do!" You don't have to be as large and glaringly obvious as a planet to have value. You just have to exist.
I hope I answered your question.