Other mistake: In the scene with the crashed escape pod, everything inside is upended with books and stuff strewn everywhere. Yet there is a bottle of Vodka sitting perfectly upright on the bar in the background.
Other mistake: Charlie gets up and goes to the bathroom, where he finds a sink full of water ready for him, although he didn't ask a machine to do it and he didn't fill it himself.
Other mistake: When Dr Shaw is in the medical "machine", and she wants an abdominal operation, a voice says, "Preparing anaesthetics," but all it does is wipe a line on her stomach with something brown - could be betadine. But Shaw screams and yells in pain. If it really is a "machine" that can perform surgery, well, surely it could put the patient under an anaesthetic that knocks them out, properly.
Answer: The giant ship has landed on Earth to drop off the Engineer so that he can terraform the planet and make it sustainable for life. He might drinks the black stuff to break down his own structure and spread life on Earth through his own DNA.
Anastasios Anastasatos