I think the oxygen is down to less than a day now, starting from a best case scenario of 96h when contact was lost.

Still sort of based?

For the second concern i like the two Hainish Circle books i have read, "The dispossessed" and "The left hand of darkness". They mention that something like earth exists, but it's not even a plot point, it's just another planet. But then again these books are social commentar / thought experiment first and foremost, they just happen to be in a Sci-Fi setting.

What's the original image?