In the DVD bonus feature "Lost Moon: The Making of Apollo 13," Jim Lovell says they didn't put their spacesuits on for precisely this reason, not wanting to be "sweaty in a cold atmosphere." Also the Apollo 13 astronauts were somewhat dehydrated because they were rationing their water; I'm not a medical expert, but if you're dehydrated you don't want to be doing something that will make you perspire.

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"One does not require alien ruins in order to absorb a profound sense of wonder and mystery from the moon. That our civilization had actually visited it is miracle enough." Jason Roberts