A seemingly logical next step - Enceladus. Sufficiently aged at over 1 billion years, with a reasonably stable orbit, the moon has an abundance of both water and heat. Its global ocean enshrouded in ice regularly spews forth towering geysers of water and carbon based molecules...methane, nitrogen, hydrogen. 'Beam-me-over' Scotty, this moon is the best bet for finding life, and well, we already know how to get there.