For me it looks like water droplets but, I doubt thats the case in space. Also I don't understand why this should be a crafts surface feature. wouldn't one aim to design a spacecraft as smooth as possible? And even if this is intentional designed part of the surface what is this irregular placed rough stuff intended for?
If it is some enviroment condition: What is it and how did it get there?
Edit: Contrast-enhanced detail of the Service Module (Full image: AS17-145-22252)