Alien: Engineers. The original Prometheus script
 

http://movieviral.com/viralcast/Alien-Engineers.pdf

Finally read this and I can't understand why they didn't stick with this (except for maybe the ending). It's great and most of all, it makes sense.
Imo this would've been a classic.

Before that I read the original script for the movie that became Alien.
http://www.dailyscript.com/scripts/alien_early.html
It's nearly the same as the original but in this version there's also a pyramid on the planet. And you find out more about the alien's origin.

A little more info:
http://alienexplorations.blogspot.be...ry-behind.html