Does Mercury have a breathable atmosphere?
Mercury has no real atmosphere at all. Since it is in relative proximity to the sun, it receives gasses from the solar wind, and some gasses are produced by the radio-active decay of elements in the rocks that constitute the planet, but owing to the planet’s low gravity and solar wind, gas do not accumulate and vent quickly into space. Pressure would be nearly indistinguishable from perfect vacuum. You’d surely cannot breathe it.
