I don't know if Ridley and Damon mentioned that but....As many of you I've been thinking, that prometheus's scenario happen before Alien. Well, I watched Alien 1 and didn't found any mention of year. Then I watched Aliens - again no mention of the year....BUT. Ripley slept 57 years. And guess what.......she never heard about terraformation and she never heard about atmosphere processors, which are well described at the Weyland Website. If you take a look here you'll find that first terraformation was made on our moon and it was finished in 2039. Which means Alien 1 was bfore 1939 and before Prometheus.
So....if this is a scenario mistake, then why did they paid so much attention to terraformation on the website, wich is absolutely not mentioned in the movie?
Looks like Weylend was inspired not only by Shaw's speaches :)