if you can do that though, I think it will make a killer short answer essay
Ha ha, yep. Consider this: You only need to mention a single word to specify a field of interest: Bioelectromagnetism, for example.
And with a few words, you can express some specific goals. In fact, if you have them, you probably cannot help but express them.
"I visited the department and saw that the laboratory was equipped with tools that will enable me to continue Dr. Robert Becker's work pertaining to bioelectromagnetism."
That sentence above shows that I have done research, visited the department, and made a plan for something I'd like to accomplish during my time there.
So... as you said, it will be a killer essay if you can express some clear plans. The ability to express clear plans proves something about you. Actually, it proves two things! :-)