What sort of spacesuit would an astronaut need if she were to walk on a planet with a 1 psi (0.07 ATM) 100% methane atmosphere and -60°F (-50°C) temperatures?
A pressurized space suit is needed when the atmospheric pressure is lower than about 0.3 to 0.4 bar. Pure oxygen is breathed within the suit. So for about 0.07 bar a pressurized suit is mandatory.
But a flammable or explosive mixture within the airlock needed to leave and reenter the planet lander should be avoided. So the airlock should be evacuated from methane before filling it with a breathable atmosphere. The methane is thus moved back from the airlock to the planets atmosphere.
To minimize loss of atmosphere, the airlock may be evacuated using the pump to move the air from airlock into the planet lander.