In addition to the US Version, the US-DVD by Alpha Video also contains an Italian Version as bonus. The following comparison illustrates the differences of these version. Unfortunately, English subtitles aren't available. In total, there are more than 100 differences. Basically, one could say two things:
1. The Italian Version contains an additional subplot about some kind of War in Space so that it seems as if space ships are permanently chasing our "mothership". They are the reason our crew loses contact with the control center on earth. The problem is: there's no real explanation for all that which makes it look unfitting. The transition from the actual movie to the stock footage is pretty rough as well.
2. There's a stringent course of events in the US Version (given the circumstances that this movie is basically patchwork) and there are more details about the charactes / plot. Especially the Dr. Manning and Valerie character from the control center are more elaborated. They're even allowed to have some freaky future sex. Furthermore, only the US Version lets Dr. Manning explain why the colors are permanently changing.
