How to explain Enceladus' salty ocean.
Frankly, while I accept the discovery of sodium salt by Cassini
emerging from Enceladus, and the evidence it offers for an subsurface ocean.
What makes no sense is the idea the Enceladus is billions of years old.
The water would have frozen solid in that time.
It makes more sense if Enceladus is more recent; perhaps only millions
of years old, as young as the rings.