The Gentle Giants of Ganymede: (#2) (Gentle Giants of Ganymede)

Long before the world of the Ganymeans blew apart, millennia ago, the strange race of giants had vanished. All that remained of them was a wrecked ship, abandoned on a frozen moon of Jupiter. Now Earth's scientists were there, determined to ferret out the secret of the lost race. Then suddenly the Ganymeans returned, bringing with them answers that would alter all Mankind's knowledge of human origins . . . In the 21st century, on Ganymede, the largest moon of Jupiter, a huge alien spacecraft is discovered. The aliens originated on Minerva, a planet which used to obit between Mars and Jupiter but was destroyed 25 million years ago and has become the asteroid belt. Is there anything left of this ancient race?