You know I've been looking at this Europa war stuff. It's pretty cool. But I'm an aerospace engineer and I can't help but cringe a bit everytime someone talks about "freezing". You would not be freezing. Yes, Europa is cold, space is cold if you are in shadow, you? Oh, you are hot, very hot! On Europa, there isn't an atmosphere. You wouldn't have any way to shed heat, so the real problem wouldn't be keeping warm but keeping *cool*. In the tunnles? Sure if they are pressurized, cold as all hell. Anything else? Warm.