Neptune (Outer Planets Trilogy, 2) [Bova, Ben]

In the outer settlements of the human-occupied solar system, there are rumors about what was found deep under Neptune's frozen seas when a Hungarian billionaire’s ship was lost with all hands. But the rumors are far more tame than the reality. When the billionaire's daughter mounts a mission to find the truth, her discoveries will up-end humanity’s understanding of our origins on Earth.

Bova’s hard sf novels have fascinated and educated readers for almost half a century.