[Jabbles]

> years at a time

I don't think any single crew deployment reaches a year.

> more dangerous and isolated circumstances

I think Mars is massively more dangerous and isolated. A submarine can plausibly return to port or surface to breathable air. There is no such option on Mars. Nuclear submarines are much larger than spacecraft and have much more room for comfort options. They have a much larger crew, and the knowledge that this happens all the time from many nations must be of some comfort.

[m4rtink]

IIRC British antarctic service does uninterrupted 2 yer contracts. Not Mars or a submarine but still 2 years.

[Cthulhu_]

At least being outside doesn't kill you in those ones.

There's also earthbound experiments like Nasa's CHAPEA programs (https://www.nasa.gov/news-release/martians-wanted-nasa-opens...) but they only go up to about a year.