Beyond Mars solar energy gets too weak to be useful for space missions. Add to that a thick atmosphere around a moon of Jupiter. So, how do you power a mission? You use nuclear 'batteries' called RTGs. Using them on a drone is a first though. Very cool!
https://www.ans.org/news/2025-04-29/article-6991/dragonfly-a-pufueled-drone-heading-to-titan-gets-key-nasa-approval/