This game, for me, is very fascinating. I would first like to say that I saw a couple of the movie inspirations you have mentioned. From that, I think you have done a good job generating an original thriller plot of your own.
Let's start with the positives. The plot was one of the most interesting I have seen. It was also enhanced by that little scene at the end. It was truly a cliffhanger. *SPOILER* I wonder what realizations John made? Your game here is quite a cinematic one. The Pixel-art is also well-used considering Pixel-art is usually used in kiddie arcade games, wherein here, it is used to convey a grim tale. It is also a great way to get medals. Hehe. I'd like you to concentrate on the positives more and improve on these. You did well in keeping your overall atmosphere consistent with your theme.
Next will be some of the negatives. I hope you won't dwell to much on these and I hope you let them serve as guides for improvement. First off, the game was quite short. It also lacks the element of exploration and always leads the player to where to go next. The walking speed is a bit slow, but I guess that adds to the suspense. You could've added a short prologue. In the real world, there is not only a single astronaut who goes out on his mission. There is a team. Well, I know it's a bit overused. You might want to think of a completely original plot rather than making things slightly similar to classic terror films. You may also want to consider making a game with a non-linear plot. So, the player will be given choices which, in the long run, can kill or save the protagonist.
Basically, I liked your game but there are still some things that could make it more dynamic. 4 stars.