Character mistake: In the first scene inside the Prometheus, after she comes out of deep sleep, Vickers asks David for a robe, and asks "how long?" meaning how long have they been asleep. David, a robot, answers "2 years, 4 months, 18 days, 36 hours, 15 minutes." The actual statement from this highly precise robot character would have been "2 years, 4 months, 19 days, 12 hours, 15 minutes."
Character mistake: The ship travels approximately 35 light years, yet Vickers (Charlize Theron) comments they are half a billion miles from Earth. That would barely get them past Jupiter, much less another solar system.
Character mistake: When Millburn introduces himself to Fifield, he has a Southern accent. For the rest of the movie, the accent is gone.
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