Would you like NASA to fly a drone across Saturn’s largest moon, or to send a probe to collect samples from a duck-shaped comet?

From a dozen proposals to the agency’s New Frontiers competition — not unlike an interplanetary “Shark Tank” for a forthcoming robotic mission — NASA announced these two finalists on Wednesday.

“It’s one of the most difficult programs to be selected for,” said James L. Green, director of the planetary science division at NASA. “We fly only about two of these types of missions per decade.”

In the first proposed mission, Comet Astrobiology Exploration Sample Return, or Caesar, a spacecraft would go to Comet 67P/Churyumov-Gerasimenko, previously explored by the European Space Agency’s Rosetta mission, and bring back a small chunk to Earth for closer study.