Make it short, no spoiler, they never actually go to Mars, and it has a twist ending.
I didn't remember a bit about it until the part where the Russians start digging up the vestments and the next bit. That was as clear as if I'd seen it yesterday, wonder if that was used it some other movie as stock footage or something.
And while it's been many, many decades since I've seen it (I expect I saw it when it was released) I was reminded of "The Next Voice...".
Good one, thanks again.