I’ll say it anyway: Take On Mars heads to Steam Early Access1 Aug 2013
Take On Mars positions you as a Rover Operator, giving you control of a variety of Mars Rovers and landers with which to investigate Mars and its history. The Early Access version comes with the Space Program campaign and individual scenarios (although I have no idea how much of these two are included) as well as a 3D scenario editor and modding support, with Steam Workshop integration to be added later.
Bohemia are apparently wanting to do this as an Early Access title in order to “work together with players to create the most dynamic exploration sim game possible.” Sort of like what they’re doing with Arma 3, then! Only that’s less focused on exploration and more on being shot 15 seconds into starting because you stood up at the wrong time.
If you want to try your hand at piloting a Mars rover around the red planet, Take On Mars will run you a fairly negligible £8.99.