Space Jockey's blood?!

Hey everybody! I'm a new member of this awesome forum dedicated to a movie that I'm hoping will blow all of our minds! Furthermore, I'd like to applaud the whole of this community as many of the people posting on this forum are true aficionados of Alien and things related to that seminal film. On to my question though, and I apologize if this has been posted prior. If the xeno had acid for blood , does anybody have any theories on what the Space Jockey/Engineer's blood is like?! Possibly taking into consideration that if Sir Ridley has stated that there will be no xenos in this film, yet at least one crew member appears to be injured by something acidic, does this acidic burn have anything to do with the Space Jockeys/Engineers?!