Themes in the Book
The Martian Chronicles only makes a handful of rhetorical arguments, but it does so quite emphatically. Perhaps the dominant theme involves the way that we as humans view our surroundings as our property, no matter what effect that belief has on the other species in our surroundings. We feel it is our right to bring our values and practices into new situations, with little consideration on how those ideas will bring long-term destruction.
In the book, the colonists are coming from Earth to Mars to flee atomic war. They land on the planet with a rocket that spews all sorts of fumes into the environment; they bring diseases that ultimately wipe out the Martians, much like the diseases that came from Europe with the colonists and wiped out many of the Native Americans. Their children run through the beautiful Martian architecture, gleefully smashing stunning examples of fine art.
The Earthlings are by no means the only guilty parties. The Martians try several different strategies to wipe out the Earthlings without first finding out their reasons for colonizing. However, the idea that, particularly in the West, we have developed a consumer society that either willfully or blindly destroys its surroundings and then moves on to fresh land to ravage, is one that appears through every mission's arrival on the Red Planet.
There are several minor themes at work. One is the effect that nostalgia can have on people (note the crew lured to its death by the ghostly appearance of dead relatives, who are really Martians trying to kill the invaders). Another is the pride that takes human achievement and makes it a menace -- the pride we take in the things we accomplish makes us demand recognition; several instances of this occur during the arrival of different crews.