Review
Continuing the story began in "Inherit the Stars," this is about the discovery of a corpse on the moon, dressed in a red spacesut, that happens to be 50,000 years old. Further research on the corpse, and the items found with it, and further discoveries elsewhere on the Moon, lead to the conclusion that there was a planet, Minerva, between Mars and Jupiter. The planet was dying; a rising level of carbon dioxide would soon render it uninhabitable. Various methods to fix the problem were considered; meantime, two factions on the planet fought a major interplanetary war, which destroyed the planet. Part of it became the asteroid belt, the other part became the planet Pluto. The human discovery of an alien ship under the ice on Ganymede, and at least 25 million years old, leads to human ideas about the solar system and man's origins getting a major overhaul.
One day, the makers of the ship, called Ganymeans (for Ganymede), show up on Ganymede. The humans had unknowingly activated a distress beacon. It is easy to imagine their reaction at being told by the humans that their planet was gone. They had gone to a nearby star to see if it could be artificially made brighter, to combat their carbon dioxide problem. It didn't work; the star went supernova. The propulsion system on their ship was working, but the braking system had failed. They spent 20 years of ship time traveling faster than light, before they could slow down. meantime, the universe was 25 million years older.
They were homeless, as well as physically and emotionally exhausted. They were welcomed on Ganymede, where they gave human science a huge boost, and were able to repair their ship. They were welcomed to Earth, to stay, if they wished. There was the usual bureaucratic nonsense about what country would host them; the Ganymeans decided to land in Switzerland.
The aliens were totally welcomed, practically as long-lost brothers. As time went on, they traveled all over the world, seeing everything, and speaking with many Earth scientists. After six months, Garuth, the leader of the Ganymeans, announces that they are leaving. The archives mention that a group of Ganymeans traveled to a place called Giants' Star. Admittedly, it is a very remote possibility, but if there is a chance that there are more of their kind at Giants' Star, it must be investigated. That is the official reason for their sudden departure, but it isn't the actual reason.
This book is also heavy on the science, but it is still a very interesting story, not just about the origins of mankind. It's very much worth the time.