Various sci-fi movies treat Mars atmosphere differently, anywhere between "you just need oxygen rebreather" and "Your eyes will pop out and your head will explode". Meanwhile, I haven't seen any solid scientific data on human surviving requirements in Mars conditions.
Surely the suit would have to be warm, probably with active heating or at the very least good insulation, like aerogel. Surely one would need to at least provide oxygen, probably the neutral gas too to prevent acidosis from Mars' CO2 in its atmosphere. But how would human body react to the pressure? I'm aware humans can survive in pressures considerably lower than normal, with correspondingly increased oxygen content - Apollo cabin pressures were about 25% of Earth's atmospheric pressure. How is the situation on Mars?