Other Bodies
Planets are not the only interesting places to explore in our solar system. In addition to much-beloved dwarf planet Pluto, there is a number of small rocky bodies waiting to be visited.
One potential mission that NASA is currently looking into is a Comet Hopper, which would land on Comet Wirtanen and watch it change as it approaches the sun. The probe would have the capability to hop from location to location on the comet, mapping out and exploring much of its surface. The mission is competing with the Titan Mare Explorer for funding from NASA.