For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
A Man Goes on a Journey
In "Rocket Summer" to "The Third Expedition," various people try to make it on Mars—and fail. If this were a classic myth (which it kind of is), this would be the part where the hero (Humanity!) sets off on an adventure.
Act II
Strangers Come to Town
In "—And The Moon Be Still As Bright" to "The Martian," people settle on Mars—and sort of succeed. In a classic myth structure, this would be the bulk of the adventures.
Act III
And Then Everyone Leaves
From "The Luggage Store" to "There Will Come Soft Rains," although people want to settle down on Mars (which is one common end to a classic myth structure), they end up returning home to Earth (which is the other common end).
Coda
Then there's "The Million-Year Picnic," which is sort of a final coda or epilogue at the end: although everything is pretty terrible for everyone else, there's still some hope on Mars.