Someone found an object that looks like a fossil. It can't be scanned so maybe its not intentional. However, Frontier should add such fossils with alien symbols or creatures in the rock. It's easy to add, because it are static objects that don't require animations.
Not sure what that would bring to the party.
How do fossils get there when there's no atmosphere?
I would say the same way Guardians or Thargoids.
Guardians and Thargoids seem to have constructed stuff on airless planets for their use, refuelling or whatever. They didn't live and die there, and they certainly didn't fossilise in the vacuum.
I assumed those places with Guardian ruins were once planets with atmosphere that became devoid of life during their wars. My bad. Must read more Guardian Lore.