I will say I'm 69(Te-he)% in agreement, the zombification and Timetravel make sense to him being there against you and looking older. But I still have a little issue with it. Clarke was a CHEMICAL engineer not a physicist, why would he be working with the Teleporters like he does as a Chemical Engineer, that doesn't make sense. But, after working however long he was there he may have learned his way with the teleporters so I will say it is Clarke.
(If calling him an engineer isn't right I apologize, but that is the closest thing I could think to call him. )
Wait.... MAYBE.....he is actually....ISSAC CLARK!!!!115?!!!! :!: :!:
In case you haven't played it, I was referring to Dead Space.