Just orbiting Mars? They are like millions of miles from Earth! Maybe you could use a tier 1 just form Mars to the moons, but I don't think it would work from Earth. This brings up another important debate: Why should the tiers remain uniform where ever you are? Tier 1 rockets probably cant get farther than the moon from Earth, but I can travel from the Asteroid belt to the moon with the same rocket! And another good point was how mars couldn't have Coal. Even if it did, what would you use if for? Everyone uses electric furnaces . You couldn't even burn it because of the lack of oxygenThe only thing I can feel uncertain about is deposits of coal. Like Ezer said, Mars was never likely to have been a lush world. There was liquid water running on its surface once, but that was a relatively short era. The planet also lacks any notable tectonic motion that could bury all that organic matter in the first place.
It's not that I'm saying it's absolute or unrealistic, but seen through a gameplay aspect I think it's reasonable considering the player couldn't previously mine coal on the moon. If it would become necessary for whatever reason, one would be required to produce charcoal locally by putting wood in an electric furnace.
About the possibility of visiting Phobos and Deimos, I think you'd only require a tier 1 rocket to reach them. They are just orbiting Mars after all.