The mirror fogs up first, before I'm even in. That's the whole atmosphere, right there, on a small scale: warm water hits cold glass and leaves a film I have to wipe away with my hand to see my own face. Up there, the thing that keeps every one of us alive is a band of blue so thin you'd swear you could scratch through it.
Thinner than the shell of an egg, proportionally. I did the math once, on the flight home. It didn't help.
Down here I stand in a fabricated rainstorm for eight minutes. I turn a handle and warm, clean water falls out of a wall on demand, and I have the nerve to do it while thinking about a meeting. The water goes in a circle: from a reservoir, through pipes, over my shoulders, down a drain, back to some plant, back to the clouds, back to me. All of it inside that eggshell. None of it leaves.
I used to towel off fast. Now I stand there a second too long, dripping on the mat, watching the steam curl toward the vent.
There is no shower anywhere else. Not on the Moon, not on Mars, not in the whole black stretch I stared into for six months. Just here, in this one warm room, on this one wet rock, a person standing under falling water with his eyes closed, safe enough to be bored by it.