« The Engines of God » Jack McDevitt

Two hundred years ago, humans made a stunning discovery in the far reaches of the solar system: a huge statue of an alien creature, with an inscription that defied all efforts at translation.

Now, as faster–than–light drive opens the stars to exploration, humans are finding other relics of the race they call the Monument–Makers — each different, and each heartbreakingly beautiful. But except for a set of footprints on Jupiter’s moon Iapetus, there is no trace of the enigmatic race that has left them behind.

Then a team of scientists working on a dead world discover an ominous new image of the Monument–Makers. Somehow it all fits with other lost civilizations, and possibly with Earth’s own future. And distant past. But Earth itself is on the brink of ecological disaster — there is no time to search for answers. Even to a question that may hold the key to survival for the entire human race…