The original marker is not real. It was a fake, that was "reverse engineered". Obviously not the artifact made by the gods millions of years before. And if you think about it, there is at least 100 feet between where you can get attacked by Necromorphs, and where the artifact is. This is in the original game of course. How do you think that -what's her name- managed to take the artifact back through the facility? She only got taken out by Hivemind after the artifact was hidden from view on the front of the ship.
Ps: Do you think that Dead Space 2 will be a continuation of the original game, after you find your girlfriend as a Necromorph on your escape shuttle?