Two questions.
There never was a real explanation about what the astronauts encountered in space to change them.
More important was why did two of the men die instantly but the third makes it back to earth in human form until he changes later? Why was he different?
I don't think the movie ever addressed it. It's a standard Sci-Fi trope. Sole survivor of a mysterious occurrence in space. It's the set-up for the real story.
shareI got the idea that the creature was an invisible or microscopic energy form whose "nature" permitted it to exist both in space, sort of dormant, or to invade living organisms. It also must have had the capacity to penetrate the ship's hull. My guess is that it quickly spread to the first two astronauts and its assault on Victor Carroon was perhaps interrupted by the shock of the ship's re-entry and crash. By the looks of him, Carroon had not yet been heavily infected/taken over when he was pulled from the ship, so perhaps the creature took all the previous time absorbing the other two astronauts. Another issue is why the creature absorbed the other two, but used Carroon as a vehicle of half-human/half alien hybridization. I have no idea why Carroon was spared complete absorption, only to be saved for the horrific transformation that ends with "him" crawling up walls and nesting in the cathedral.
sharenot bad
share