So, I've been out of this discussion so far, didn't want to pour fuel on the fire. 

The main thing we need to think about here is what kind of situation we want to put our characters in (on the planet). Are we alone or is there other groups like ours but we got separated on the way down? 
In the first instance I could see a catastrophe similar to what Anarchy described happening. Because of the extremely low survival chance it would make sense that we're the only ones who made it. 
If we're supposed to have backup somewhere I'd use something like Clocktower's infiltration-idea, much higher chance of us running into friends along the way. 

Personally I like the idea of us being alone, but the whole "mystical artifact that can kill everything" just doesn't sit right with the setting. Personally I'd modify the infiltration-idea and simply make their attack so stealthy that the soldiers didn't have a clue until it was too late and simply blow the ship to kingdom come.