I'll start with the bolded part and also by saying what I state doesnt make me wrong or you right nor vice versa - just offering something for consideration.
Personally I do not see a large distinction between a purpose and meaning for living, both are intertwined. The only way there can be a distinction is if there is a higher being (for lack of a better term) that created us, in that instance their purpose would be our "meaning". That is my interpretation on the meaning of life anyhow.
In the last century the discoveries we have made discount the need for the existence of gods to give meaning to our lives and tell us that the unfortunate reality is that we are an accident at best. That can be quite a lonely concept because humans, despite the fact that we feel free and individual, we like prescribed direction. However, what we know is that the uiverse is insanely massive and we are a minute blip on the radar that might never be remembered and quite easily forgotten in the sands of time. Getting off this rock and stepping on the moon gives hope, but getting out of this solar system and going beyond is unlikely to happen from the research I have done. It is more likely we end up wiping each other out and have all eveidence of our exitence washed away from the universe completely when our sun goes supernova or when Andromeda impacts with our galaxy.
I'm unsure that this is the reason for human exploration. Many people have an innate thirst for knowledge of the unknown, we are now seeking legitimate evidence based explanations to these unknown quantities, travelling to the moon was a natural step, as is travelling further from our planet.
Traveling to a satellite 380'000 km away, and an Earth like planet to evacuate to in another solar system, is two incomparable achievements. We are a victim of our own success in the fact that we are so well adapted to Earth, that a planet we could live on would have to not only be the right temperature for water to exist, but also the right mass, time of rotation, gas proportions and many other characteristics all need to be similar to Earth. Although there are billions of planets we could live on in the universe, the universe is a very large place.
Again, I must disagree.
These two achievements are most certainly comparable, clearly travelling to a distant Earth like planet is much more difficult than travelling to the moon, however they can be compared.
Fortunately we are a very adaptable species, moreso than any species this Earth has seen (that we have knowledge of). A planet would not necessarily need to fit all of these parameters in order for humans to exist there, the technology we have at our disposal now and into the future would allow us to live on a wide variety of planets. While humans could not be self sufficient on Mars, it is certainly not beyond the realm of possibility that we inhabit the planet in the near future.
I did not mean to imply that the universe would collapse. On the contrary Dark Energy appears to be pushing it faster apart when viewed from our position in the universe. Given the universe appears infinite (or as close as makes no difference) and expanding, it stands to reason for me at least that when you place a finite amount of mass and energy forever expanding in an infinite space - it eventually will all dissipate so far apart that existence of matter and energy is so far apart there is simply nothing.
I am liking this thread! I'll try soon to make a post on topic in relation to leaving a mark.
The ultimate fate of the universe is at this point in time unknown and any theories are essentially speculation with very little evidence. What constitutes the universe itself is not fully agreed upon, with many believing the universe is creating the space it expands into as it expands, rather than expanding into space that is already there. So there is not an infinite space as such, there will only be infinite space if the universe continues to expand, which it appears it will. However the basis of what you're saying is certainly a valid theory, while it does sound a depressing idea, the reality of this is so far in the future it is incomprehensible.