I went in knowing that the ending would turn into a "slasher", thus I figured that one of them- onboard Icarus II- would go insane. This furthered when I started seeing the tension between the characters, the fights that break out, going into depression, and the suggestions of taking human lives in order to succeed in accomplishing the mission.
However, at the end it turned out that all of this came from Penbacker a survivor of Icarus I.
How did he survive? Throughout the entire film it was suggested that if they were to kill a couple of the others there would be enough oxygen to allow the mission to progress and for them to survive- even at the cost of a couple of lives.
I imagine the Icarus I running out of supplies and a sense of paranoia overtaking the ship, knowing that they might soon die. Due to this Penbaker begins to go insane and kills all of the people on board and then places them in the observatory room so that they would burn- thus, losing their identities in a sense... over the span of the seven years, Penbaker survived on the ship. Isolation and being alone for that long, I'd imagine can cause one to go insane- and from the video feed he already had a screw loose in his head which didn't help matters.
So, to put it simply Penbaker is the representation of what the members of Icarus II could have become and might have become because there were many times they were considering turning to murder or allowing someone to die just so that they may survive a second longer. In short, Penbaker was the physical representation of these psychological fallouts that the crew was having throughout the film. Their own demons manifested.
Overall I found it to be a very interesting film, great visuals, great characters and an interesting ending that reflected the character's inner demons. Lives are expendable, but at what cost and how does one determine such a cost?
