A Future Ancient Secret

The Stars Are Also Fire, 7.

A novel set in our future can still feature a mystery from long ago - from it's characters' perspective:

the Selenarch Niolente had sent several missions into deep space;

their purpose was never divulged although they seem to have given her the confidence to maintain her resistance to the World Federation;

when the Federation incorporated Luna, the Peace Authority appropriated all of Niolente's databases; 

before the contents of the databases were released, it was implausibly claimed that some files were accidentally wiped;

earlier, a son of Dagny Beynac had not returned from a deep space expedition;

Lilisaire is sure that his discovery, whatever it was, was what Niolente later investigated;

the Fireball Trothdom lodge master, called "the Rydberg," guards some secret from that period;

"'...the first Rydberg was the first child of Dagny Beynac...'" (p. 106)

OK. Here is an ancient mystery in our future. The Federation suppressed some information that might be important and that be known to the Rydberg...