[Spoiler] Humans on earth

[Omnitool]

And what about the space programme? It's the 2100's they must have been able to establish a self sufficient colony on the Moon and maybe even on Mars, or at least on the International Space Station.

If that sounds too far fetched, there are people living on the international space station today...by 2100 the space station should have been extended to host more people, possibly even become self sufficient regarding food and water. The present day space station is already self sufficient to some extent, as it is powered by solar panels and a small nuclear reactor, and they are researching ways to grow food in small hydroponics aboard the station, and have very powerful filters that recycle waste water into drinkable one.
There should be at least 10 - 15 people aboard it by 2100, and they should have been able to stockpile enough food and water to last at least for a year or even two, knowing beforehand the comet will hit Earth.
The game hints that space exploration has become a bit easier due to the low cost space launching via the Omega cannon from station Phi.
The only possible explanation would be that either there was an inhabited space station, but the comet hit it before Earth or dragged it out of orbit, either that humanity lost all interest in space exploration (it seems to be happening today in comparision with the 1960's) due to economical issues or other reasons.

Also, in the game we learn as a fact that the comet struck in the ocean, not the continental mass. If this is the case then it would most likely have produced a very high tsunami, wiping everything across the face of Earth (like in the 2012 movie), but then the waters would have gradually retreated...and there is no logical explanation for the fires "reaching all the way into the sky", unless:
A. The comet caused intense volcanic activity afterward.
B. Upon impact the comet poisoned the atmosphere with some highly flammable gas contained within it, causing the oxygen in the Earth atmosphere to ignite.