Lacuna Passage is an upcoming Unity-based game by Random Seed, which puts you on the surface of Mars. Real Mars, not sci-fi Mars.
You play as the astronaut Jessica Rainer, sent to Mars to investigate why the first mission to Mars disappeared.
Described as as "open-world Mars exploration and survival game with a mystery to uncover", it's a safe bet whatever got the first mission will also try and get you.
OK, so there's probably some kind of sci-fi twist to it, but on the whole, I love how it's prioritising the brutality of just existing on an alien planet, making simple things like gravity, oxygen and air pressure the most important things you have to worry about.
Kim Stanley Robinson's Mars trilogy are my favourite sci-fi books of all time because they do such a good job of representing this, so it'll be interesting to see how fun it is to actually play.
You can follow the game's development at the link below.
Lacuna Passage [Site]