Ok, so the Domain was a precursor construct which means that there was some organic matter used in the making of it. So when the Halos were fired the Domain along with the star roads were destroyed right? Because if the Domain wasn't destroyed then there is still some plausible hope for Cortana that 343 might use to bring her back. Because she was all over the rings, and the Mantle's Approach which might mean some record of her may still remain in the Domain if it still exists. Is there any possibility that the Domain survived?