If some humans went to another planet and they lived there for many years would their off-springs become a sort of subspecies?

So I'm working on creating a character for a story and I have an idea in which there is a difference in the class of people (not necessarily through the whole rich and poor situation) based on how they were produced. I'm having a tough time putting into words what I'm going for so I started doing some... show more So I'm working on creating a character for a story and I have an idea in which there is a difference in the class of people (not necessarily through the whole rich and poor situation) based on how they were produced. I'm having a tough time putting into words what I'm going for so I started doing some biological reading in regards to subspecies. I think I'm thinking in terms of "locality" or some form of genetic choosing (it's actually something similar to a lab that exist in which the parents can choose particular traits for their child based on a database of, I guess sperm given to the lab by the father), I was thinking that something similar would be classified as one field/group of people.

So the question about Mars is mostly, how far along would humans have to be from one another to be considered a subspecies. From what I've been learning, it's possible that if humans were to go to Mars of live somewhere else where the conditions were different from Earth that they would experience a sort of physical change to adapt to their new environment. But this wouldn't change their genetic make-up would it? It also wouldn't change any of their internal organs either, right?

Any information or links would be appreciated. I was planning to create a made-up environment where different subspecies of humans exist. I know it's fiction and all, but I'd like a foundation to work from so that it will at least make some sort of sense. I hope my question makes sense. Thanks in advance!
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