How big would a manned ascent stage for Mars need to be? assumes 3 astronauts. That question appears to draw inspiration from the Apollo programme, and the Soyuz evolution. Part of the rationale behind the 3-count is mentioned in Why have so many space missions had a crew of 3?
Yet a manned mission to Mars, or any celestial body other than Earth's Moon would probably be significantly different from the Apollo Program; if only because of the time-scale involved given contemporary technology.
How would one come up with an optimal team-size for a manned mission from Earth to a celestial body other than Earth's Moon?