Undergraduate / 'the field of aeronautics and astronautics' - MIT: Describe the world you come from [4]

Terse and to the point. Really well-developed. MIT admissions will definitely be impressed!

Undergraduate / 'research and internship opportunities' - Johns Hopkins - supplement #1 [2]

I think it is obvious that you like science and that you want to major in biology. So hooray on answering that part of the prompt :) the part of your essay that doesn't really appeal to me is the introduction. To me, personally, it is not a catchy intro and if you changed it I think that is what would keep Johns Hopkins really interested in your answer.