Ron Greeley at ASU wants the next big planetary mission [top] to go to Jupiter's moon Europa to probe the planets ice shell with radar, geology, and chemistry for signs of an underlying liquid ocean that might hold life.
Jonathan Lunine of UA argues that a mission to Saturns' moon Titan offers something for all aspects of planetary science. The mission would include an orbiter, a lander aimed at one of Titan's liquid methane-ethane lakes, and a nuclear-powered hot air balloon [bottom] that would circle the moon.
Greeley and Lunine make their cases at a NASA meeting held recently at ASU in Tempe. NASA is holding a first-ever head to head competition between competing planetary proposals with the these tow projects making the first cut. One will be selected by the end of January.
This is gleaned from a great article on the meeting by Richard Kerr in Science.