On A Planet Alien

Folsom's Planet - An Alien land yet so familiar.

If the mission were a success, Folsom's planet would bear his name for eternity. The barbarians would be civilized; the planet would join the Federation; the Federation's integrity would be preserved.

But Hans Folsom had to be on guard. The aliens were intractable, his crew possibly traitorous. There was an incident during the voyage he couldn't quite remember. And a prophetic runic stone.

Had ancient spacemen visited here in the past? Did that explain the strange religions, the ancient ruins, the mysterious runic stone?