It must be a woman who is first on Mars

The assumption that there will be no such thing as humans is highly likely to be correct.

To assume otherwise requires two massive assumptions, firstly that our species will not via some self-inflicted or natural disaster become extinct, and secondly that if we avoid that we will cease evolving as a species.

So even if our species does not become extinct, over such vast timescales we would be highly likely to evolve into something very different.

As far as the inevitable demise of our planet as a habitable world in the distant future, it is indeed so far into the future that it is utterly beyond our ability to give a shit. Because either we or some other species will evolve technologically into a species that will be able to deal with it. Or we won't. Either way, there is nothing much we can do about it now beyond trying to ensure our own survival as a species, so that our distant descendants have a chance of evolving into something that can outlive our world. And that is all we can do.

In contemplating our futures we tend to be constrained by the limitations of our own lifetimes and of those we love. Anything that happens after our death makes zero difference to any of us personally. But most of us do have much younger loved ones whom we hope will have many more decades left after we have gone. This does mean that because we care about them, we do concern ourselves with the immediate decades after our own deaths and wanting them to be good ones for our loved ones. But anything much beyond the expected life spans of our loved ones does not tend to concern us much emotionally. We can contemplate it logically and rationally - we can think about a future many centuries from now - but we have very little personal emotional investment in it. We tend to leave worries about that to future generations, not our problem. And that is just a few centuries into the future. None of us are going to lose any sleep worrying about the situation in millions of years time.