I am a graduate student at the Department of Earth and Planetary Sciences at the University of California, Santa Cruz.
I find all of planetary science equally interesting, but my current research focuses, with the patient advising of Prof. Erik Asphaug, on the Small Bodies of our solar system — comets and asteroids. These small bodies are interesting to different people for different reasons. Planetary scientists look at these bodies for clues on the details of solar system formation. They believe that knowing exactly what comets are made of is a way to test different theories about the way our solar system formed. And asteroids have been colliding with planets for most of the solar system's history. Studying the evidence of these impacts (known to us as craters) is a way to learn about both the impacting asteroid and the target planet.
More practically minded people note that these planetary collisions are still an active hazard! Earth has a decent surveillance program for tracking possibly hazardous asteroids, but plans for actions in the case such a dangerous event is predicted are barely starting to form. Indeed, without knowing more about what typical asteroids are made of and how they respond to various "energy depositions" there is little hope of designing a successful diversion mission.
Studying comets and asteroids almost invariably translates into writing and running large scale computer simulations, which is the main reason I got into this field! I enjoy applying Computer Science techniques to scientific exploration and research. Small planetary bodies are challenging to model numerically, but this is exactly where the fun begins.
The Research section has more information on my past and current research projects.