Solar storms, the darkness did something to the sun so every now and again it flares out in wild storms sending waves of solar radiation throughout the system, coming like lightning storms every now and again and the radiation waves as frequent as the lightning, but your ghost gives you a warning telling you to take cover behind something sturdy or risk being blasted away in a puff of ash. And the best part would be knowing that if you're on earth when it happens, you know that the Mars dwellers have it coming in only a few minutes too, and so on and so forth