I think there could've been life on Mars because look at the canyons and there seems to have been large amounts of water there at some point to
another, and there could still be, and that there are some shins of archetecture on Mars.
They have already proven that their is frozen water at mar's poles. I think that there either was life a long time ago, or that new life will slowly
start developing.
I'm sure there was once life on mars, even if it was some form of bacteria to an intelligent life-form. I think Mission to Mars might have some truth
to it, who knows maybe we were pollinated from off-world beings.