It’s against the current guidelines that say that you should use the exact title, but I don’t like this part of the guidelines. (But there are some horror stories of heavy editorialized titles.)

On the other hand I didn’t know Enceladus until today. (I fist thought the story was about Titan.)

My preferred title for the HN submission would be “Enceladus, A Moon of Saturn, Has a Sea” or “A Moon of Saturn [Enceladus] Has a Sea”.