The air would not be polluted with the passing of this train of blimps. Solar panels on the top of them, powered the thrusters that moved them forward. The atmosphere of Mars would not support the flight of normal Earth style aircraft. It was too thin. They could make a combination of gasses that was more bouyant than the weak atmosphere that surrounded them. The configuration of one behind the other, worked much like race cars drafting each other, so that all of them would move faster.
Grand plans of terraforming the red planet to be much more like the Earth nest the had pioneers had flown from were dashed. What water there was on the planet was eigher in the polar ice caps or frozen underground. It turns out that the fantasy of a once flourishing planet going dry, and evolving into the vast carved deserts was just that...fantasy. Mars had always been cold and dry. Much of Mars' surface was covered with a mineral called Olivine. It breaks down very quickly when exposed to water, and the fact that it covers so much of Mars, means the geological history of the planet never had a period of wetness. All of the canyons and seemingly dry river beds were carved by the wind.
The planet has a permanent human presence. At least as long as they maintain the means to survive in this hostile environment. They are mainly believers in an apocolyptic future for Earth. They believe that the human race will destroy itself and the planet Earth. Their outpost colony on Mars would be only surviving members of our species. They don't have a name for themselves, because that would make it seem too much like a cult. It is just people who have similar beliefs about the Earth's future.
They are comprised of numerous different organized religions, and an unusually high number of agnostics and a smattering of athiest. It may be that it takes a lack of belief in a conscious higher power to believe that the fate of humankind is in their own hands, or just subject to the laws of nature and the survival of the fittest. It may be that they are right, but given the lack of resources on the planet and the relatively low number of people, they will never venture on to other star systems or planet. Given time and inbreeding, the human population of Mars will dwindle away withouth the fresh genes and supplies of Earth. So what will they have accomplished in the end?