Best guess: Different types of xenonite are optimal for different situations. They had no idea what my air was like. So they want to test various compounds against it. When I leave the tunnel, they’ll inspect the hexes to decide which one fares best.

That means I should leave the tunnel. Should I depressurize my side for them? Seems polite. I could easily do it—I’d just tell the airlock to cycle. It would think, “Golly, there sure is a lot of air in me today!” but would just keep pumping until there was a vacuum.

But then again, maybe they have a way of sampling the air on this side. If so, I should leave it here, right?

I decide to leave it be. They probably have a sampling technique. If I were making this tunnel, that’s what I’d do, and they seem pretty bright.

I turn back toward the airlock, but something catches my eye. Movement!

I shoot my attention back to the hex wall. Nothing’s changed. But I could swear I saw something move. Some of the hexes are shiny—I probably caught a glimpse of my reflection.

Wait…

One hex stands out. Why?

It’s near the tunnel wall. Not very obvious. I float over to take a closer look.

“Holy cow!” I say.

This hex is clear! All the others are opaque, but this one is like glass! I pull one of the lamps off the wall and hold it up to the hex. I press my head against the hot wall to get a closer look.

Light gets through into the other side. I can see the tunnel walls beyond. Either their side is a vacuum or their air is clear. Either way, there’s nothing blocking or dulling my view.

Suddenly, a rock hits the other side of the hex. It stays there. It’s just a few inches away from me. It’s roughly triangular, kind of a dark brown, and has rough, jagged edges. Like you might see on the tip of a spear from a caveman.

Have I met spacefaring cavemen?

Stop being stupid, Ryland.

Why did they put a rock there? And is it sticky? Are they trying to block my view? If so, they’re doing a terrible job. The little triangle is only a couple of inches wide at the thickest point and the hex is a good 8 inches across.

And it gets sillier. Now the rock is bending at articulated joints, and there are two similar rocks that do the same thing, and there’s a longer rock attached to them that—

That’s not a rock. It’s a claw! It’s a claw with three fingers!