In engineering and many branches of economy, it is custom to provide a minimum viable product:

A minimum viable product (MVP) is a version of a product with just enough features to be usable by early customers who can then provide feedback for future product development.

This maximizes development speed as basic features can be tried out and tested while new features are being developed, thus minimizing feedback time and maximizing deployment speed.

What is the minimum viable product for a mars mission? I think it is reasonable to guess that it is a life support system, as it is already being deployed on the ISS, just on another planet. This minimizes new development work before a usable variant can be deployed and allows re-use of established technologies.

This would mean that the type of life support system that’s already being used on the ISS today is simply re-packaged into a new ship and used on-ship and on-destination as it is being used on the ISS today.

Apart from the minimal feature set, there is some valid criticism with this approach, such as:

• in case of emergency, no quick rescue mission is possible because of the long distance.
• the mission duration would probably have to be longer until enough fuel can be produced for a journey back, which increases exposure to radiation and unknown variables

Essentially, it would be a leap of faith that the type of mission that has already been happening on the ISS for the last 25 years, can also still function well enough if it’s deployed at a much more remote location, and for significantly longer durations.