We brought them with us accidentally, or maybe they were secret smuggled pets for someone who worried they might get lonely. They'd've been right to worry: it's really lonely on the moon.

 

However they got here, the mice were a real problem. No cats or owls to keep them in check up here—nothing. Only what we'd brought with us—and if the old world tells us anything, hanging sad and dead there above our little bubbledome, it's that the thing we bring with us wherever we go is our own ruin.

 

The mice have had many generations now to get used to the moon: they're bigger and longer than old-world mice, eyes wide and round like the moon itself, their fur a pale, luminous grey, grown thick against the forever chill.

 

They tried trapping them, but the mice danced slow and dreamlike out of the guillotine-wire jaws and slow-closing gates with their morsels of precious freeze-dried cheese, to lay their droppings among our dwindling supplies and gnaw on our vital wires.

 

So they set the kids to mousecatching. We haven't had the generations the moon-mice have to get used to this place, but sometimes we felt that we were already better suited to the moon than our parents, our eyes wider, our fingers longer, our hops a little faster, the many tones of our skin all inching toward grey.

 

I was a good mousecatcher—maybe the best. I was always small, and I'd learned for my own reasons to make myself invisible in the world. To be still, and suddenly quick. And maybe I had a mind like a mouse: a mind of narrow escapes and huge fears and little hungers I couldn't name. Most other kids, especially the bigger ones, couldn't think like mice. They were cat people, dog people, wolf people. But cats and dogs and wolves—if there are any left—all worship the moon from afar. Up here it's just us and the mice.

 

I was still catching them at fourteen, when most kids had long since given it up, but I was that good. It was getting urgent, too. They were eating too many of the supplies before the mushroom farms got stable, spreading germs we'd hoped we'd left behind. And worst of all, they were tunneling with little diamond claws through the soft moon rock, out toward the emptiness beyond, murderous little holes in the bubble that kept us all alive.

 

"You dumb things," I'd tell them when I caught them at their digging. "You'll die out there."

 

But secretly, when I looked out at the endless cratered moonscape under the rising earth, I understood them. And when the mice I'd caught were thrown out the airlock, I couldn't help but feel that it wasn't an execution but an escape.

 

Or maybe that was just conscience.

 

Because I liked the mice, really, for all that I was their main predator. I even named the ones good enough to get away from me. One Mister Charles and I had been locked in a slow lunar race for months, he always one scurrying corner ahead. I was starting to wonder whether I really wanted to catch him.

 

It was following Mister Charles into the depth one long lunar night that I found the big tunnel. Air hissed into it in a way that told me it already went to the other side.

 

"Mister Charles," I said as he vanished into it. "What did you do?"

 

The tunnel was bigger than a mouse tunnel should have been, or maybe this moon-life and mouse-life were making me small. It was hard to tell in the depths of the lunar night, in the confusion of self that always crept upon me in the long pursuits.

 

I thought myself a mouse, squeezed myself smaller than ever, and followed Charlie through.

 

What was I thinking? I couldn't survive out there. Nothing could survive out there.

 

Except, it turns out, I could. I popped out, my hair and skin all covered in moondust. I looked up. I'd never seen the Earth not through the bubble. It was wondrous—more wonderful to me than the very fact of my being out here on the unprotected moon. Up there in the old world maybe there were wolves and dogs howling, maybe children looking up at us in wonder of their own. Or maybe they were all dead. Maybe there's no escape anywhere above or below.

 

Around the little hissing hole—how had I ever fit through?—I saw more moonmice. They bounced happily through the airless, irradiated world, surviving heedless of every expectation and every natural law. Like me. Across the shadowed moonscape I saw more tunnel exits, more mice scurrying in and out.

 

There'd never be enough people to catch enough of them, not even if all of them were as good as me. Eventually they'd try something big and desperate—poison gas or bombs—because that's what Earth-people do with their problems, and that would be the end of Earth-people on the moon. People carry their ruin with them wherever they go.

 

But maybe we creatures of the moon are different, and our desperate measures aren't big ones. Maybe, I told Mister Charles and his friends, as they sprang gentle-pawed over my grey-flecked arms and hands, they're little things: little tunnels, little escapes, little dreams of scurry-leaping across the dusty cratered cat-less, owl-less plains, in the soft blue light of our beautiful dead world.