Per this question I've been giving thought for some time to restricting the use of antimatter and it occurs to me that an object lesson in what can go wrong might go a long way to discouraging its use.
To that end what would the aftereffects of a reasonably large amount of antimatter going off look like after several hundred years?
For the purposes of answering the question one metric tonne of antiprotons broke containment on, for all intents and purposes, the surface of the moon three hundred years ago. Does the site still glow because of daughter isotopes or is it simply a big hole in the ground, how far would the debris be spread etc... The focus is really on what the site looks like, from L1, what legacy remains from this largest industrial accident in history.