Realised something on the thread about which characters didn't die with Diana according to her recording - she says she killed six people, meaning that if there were nine, then the survivors would be herself and any two out of Sigma, Junpei and Phi.
But because all three of those latter characters appear in VLR, they clearly all survived. So how can this discrepancy be handled?
My theory is this: there is an unrevealed TENTH character in the Mars Mission Site. Perhaps someone not taking part in the experiment - someone outside of the nine numbered volunteers. That way, this character can die and it adds up nicely.