蒼茫[soubou] dusky
茫然[boozen] dumbfounded
茫然自失[bouzenjishitsu] stupor
茫漠[boubaku] boundless
往事渺茫[oujibyoubou] memories of the past events (being, becoming) far and distant

往事茫茫[oujiboubou] memories of the past events (being, becoming) far and distant
茫茫[boubou] wide expanse of flat surface (e.g. sea, plains)
草茫々[kusaboubou] covered with weeds
渺茫[byoubou] vast