The Martian Chronicles is written with two main points of view: third person omniscient and third person limited omniscient.
In third person omniscient stories, the narrator can jump anywhere, including into anyone's mind. In most of the interchapters, Bradbury's narrator does just that, giving us a broad overview of large movements of people, then swooping down and telling us what those people are thinking.
For instance, in "The Settlers" the narrator tells us that the people "came because they were afraid or unafraid, because they were happy or unhappy, because they felt like Pilgrims or did not feel like Pilgrims" (2). The way Bradbury uses this perspective almost gives his writing a mythic feel, almost as though he's writing an origin story—which, in a way, he is. The focus isn't on individual characters and their motivations; it's on the movements and feelings of an entire group. Cool, but a little hard to relate to.
While the interchapters tend to feature that free-floating narrator (I'm here, now I'm here, now I'm in your head, now I'm inside your house watching you sleep), many of the stories focus on just one or two main characters.
In these stories, the narrator only gives us what this character sees and thinks. For instance, in "Ylla" we get the story from her point of view. We don't see Nathaniel York because Ylla doesn't see him. We don't see Yll kill Nathaniel York because Ylla isn't there to see that. It's Ylla's story.
Some of the stories have two characters' points of view. For instance, "—And The Moon Be Still As Bright" starts off from Spender's perspective—we see what he is thinking and doing. But after Spender kills Biggs and the other men, we start to get Wilder's point of view. When Wilder is hunting Spender, the point of view switches back and forth, until the end, when Wilder's point of view becomes dominant and we hear more and more of his thoughts.
|The Summer Night||X|
|The Earth Men||X|
|The Third Expedition||X|
|—And The Moon Be Still As Bright||X|
|The Green Morning||X|
|The Fire Balloons||X|
|(Way in the Middle of the Air)||X|
|The Naming of Names||X|
|The Old Ones||X|
|The Luggage Store||X||X?|
|The Off Season||X||X?|
|The Silent Towns||X|
|The Long Years||X|
|There Will Come Soft Rains||X|
|The Million-Year Picnic||X|
You can see that there are at least two chapters we're not entirely sure about. "The Luggage Store" is a short interchapter, but it focuses on a brief discussion between two people. Compare that to "The Watchers," which is an interchapter that tells us what all of Mars is doing.
And what about "The Off Season"? Its narrator mostly tells us what happens from Sam Parkhill's point of view. For instance, when there's a Martian behind Sam, the narrator tells us what it feels like to have a Martian behind you. But we don't really hear a lot of Sam's thoughts, like in the other stories, where we see events from a particular character's point of view.
So, what's the point of all this jumping around? The stories are a way for Bradbury to tell a much larger story: the attempt and failure (and then second attempt) to colonize Mars. Yeah, that's a big story. It's not a hard-and-fast rule, but epic and sweeping stories tend to have multiple points of view (we're looking at you, A Game of Thrones). It's hard to talk about interplanetary war or saving the world if we're stuck in one guy's head the whole time.