First Lensman by E.E. Smith

Pluto is, on the average, about forty times as far away from the sun as is Mother Earth. Each square yard of Earth's surface receives about sixteen hundred times as much heat as does each of Pluto's. The sun as seen from Pluto is a dim, wan speck. Even at perihelion, an event which occurs only once in two hundred forty eight Tellurian years, and at noon and on the equator, Pluto is so bitterly cold that climatic conditions upon its surface simply cannot be described by or to warm-blooded, oxygen-breathing man.

As good an indication as any can be given, perhaps, by mentioning the fact that it had taken the Patrol's best engineers over six months to perfect the armor which Virgil Samms then wore. For no ordinary space-suit would do. Space itself is not cold; the only loss of heat is by radiation into or through an almost perfect vacuum. In contact with Pluto's rocky, metallic soil, however, there would be conduction; and the magnitude of the inevitable heat-loss made the Tellurian scientists gasp.