When Krüger and I have warmed up and changed back into indoor clothes, we join Liu and her tablet in the common room. Even Kwon is present, though the thin lines creeping sideways into the graphs on the screen probably mean as little to her as her engineering wizardry does to me. I give the data I know a quick once-over. For a minor moon in the rings of a gas supergiant on the outer edge of a blue-star binary solar system, Mahaha is startlingly earth-like. Assuming, of course, that you're an interstellar immigrant and have lived on the relevant parts of earth. Gravity, temperature, atmospheric pressure, and even rotational period—length of day—all come within a human-tolerable distance of those on humanity's ancestral planet, all of which would lead you to assume Mahaha is habitable if you hadn't visited it yourself.

I spot the graph for wind speed—waffling between calm and gusts of up to eighty kilometers an hour—and the one for temperature embarking on its slow downward slide into nighttime. Radiation is high, humidity is low, and Liu and Krüger are both frowning.

Krüger points to a graph near the bottom of the screen. "This is from the forward sensors, not the ones on the underside?"

Liu nods.

"What the hell."

"Right?"

"Solving the mysteries of Mahaha?" I say.

"No," says Krüger. "Confirming them."

My favourite thing to hear.

Liu points to a cheery yellow line holding as steady as the surface of a helicopter pad. "That's precipitation rate." Snowing constantly. Surprise. "And that"—she slides her finger down the same graph, to a parallel blue line hovering just above the horizontal axis—"is sublimation from the surface."

My eyebrows go up. I don't need a meteorology degree to see what's wrong here; I've spent enough time with scientists to know more than my fair share about the water cycle. The water coming down from the sky on Mahaha is some sixty times more than the water going back up again.

"Updrafts?" says Krüger.

"That's what I thought," says Liu. "But that's not it either."

She taps an icon at the bottom of the page. The screen fills with a rendered 3D map of the surface around the probe. High points are highlighted and labeled with their relative elevations: the Isoptera scanning for its best perch. Liu taps a few more things, and the space above the map surface fills with a moving representation of... well, of something. Air currents or snow or local convection cells. Here and there, a column rises against the grain, but the dominant trajectory is groundwards.

"That's not a water cycle," says Krüger. "That's a waterslide."

"Exactly," says Liu. "And this is the highest sublimation rate we're ever measured."

"Twilight radiation?"

"Yeah."

Twilight radiation is the strongest we get out here. If these measurements were taken at a time of day when maximum ice was getting radiated back into water vapor to rise back into the sky, this is as balanced as the system is going to get. Which is to say, not at all.

Krüger runs a hand into his hair, knocking his glasses askew. "So it snows all the time, but then there's absolutely no sign of where all that water is coming from."

They exchange a look that says more, but neither of them fills Kwon and I in on their hypotheses.

"And then there's the surface movement," says Liu, going back to the graphs. A flock of jagged lines shows the motion of the higher peaks in the area. They're jumpier than a juvenile locust swarm. "The last team here thought it might be seismic activity, right? Well, the probe did a micro-radar test..." She clicks a file, and an error message pops up on screen.

"Holy shit," says Krüger.

"What is it?" says Kwon.

"There's no bedrock," says Krüger. "Not within five kilometers of the surface, at least. The radar isn't strong enough to reach deeper."

So there are at least five kilometers of snow and ice beneath our feet. Somehow, I'm not surprised. This, though, doesn't explain the looks on the two scientists' faces.

"So there's no reason why the surface should be moving, either," says Liu.

Ah.

I suddenly wish I'd taken a chair. The clench in my chest and knot in my stomach echo the first signs of a headache I'd rather do without. I don't like this. Ice isn't supposed to move on its own any more than Jenu's freak dust storms are, but clearly that hasn't stopped either of them. The survivors of the last team to come here were sent in for psychiatric help after raving about how Mahaha's surface was alive. Now that statement, somehow, has as much backing as any alternative.

Krüger and Liu keep exchanging glances. At one point, I swear Liu tips her head in my direction. They're going to ask for a field mission, aren't they.

"The water vapor's coming from somewhere," says Krüger. "It could be geysers like Enceladus or Maneto have—then the shifting could be ice movement over a subsurface ocean. The fly-bys never detected any open water."

"We'll have to see if the probe turns up anything." Liu's tone is breezy. "Something tells me ground searches are going to be... unfeasible."

Smoothly phrased.

I'm first to pull back from the tablet; I need space. "I'm going to go grab something to eat. Chore list for the week is on the fridge, and I expect to see rooms cleaned by tomorrow at noon. Liu, you're on breakfast rotation."

There is a collective and absent breed of nodding. None of them unglue their eyes from the tablet. I leave them to their graphs and make my way to the kitchen, as much in search of a distraction as anything. Pickings in the fridge are slim, but there's still a container of leftover japchae in the back corner. I heat myself a bowl and wander around the Pod with it, eating as I conduct my nighttime check of everything electronic. The airlock is sealed, the air recirculation system is in working order, and the many small instruments in the lab hum softly to themselves.

I climb the stairs to the greenhouse and stand in the middle of it, wishing for stars. Nothing but Mahaha's grey sky arches overhead, still glowing dimly with the light reflected off Qalupalik, the giant gaseous planet that would fill our view of the sky if there were no clouds. For one of the most remote and untouched places in the UIS, Mahaha reminds me strikingly of a smoggy earth city on a cloudy night, bathed in its own light pollution.

I chase the last noodles around my bowl, scraping rehydrated vegetable shreds together with my chopsticks. Packaged or not, food should never be wasted. When I'm done, I check the greenhouse's water tank and temperature controls before leaving this dark and quiet jungle for the lights of the main floor. Kwon and Krüger have drifted off to their rooms, but Liu is still curled in one corner of a couch with the tablet in her lap.

"You packing in soon?" I say with a yawn.

She nods. I let her take first turn in the bathroom, then occupy it myself when she returns to the common room. It's well after dark by the time I crawl into my sleeping bag and watch the blank rectangle on my wall swim with worries and memories before I finally fall asleep.

I'm not sure if Liu ever went to bed. She's back on the couch when I wake up, and I'm usually the earliest riser. She looks up as I wander in. Her face is harried, like she's got news she's already dreading.

My heart takes an unpleasant tumble. "Is there a problem?"

"I think we lost the probe."

Thank god Krüger is a heavy sleeper. The first of the now-seventeen probes we've deployed on this frost-bitten moon lasted longer than the most expensive and equipped of them all. I take a quiet breath to calm myself, then perch on the couch beside Liu. "Show me."

She scrolls sideways across the tablet screen, then tips it towards me and presses play. The stacked time-series graphs that so fascinated everyone yesterday begin to move, their time stamps flickering through the evening and into the night. The wind dies, then picks up a little, and the probe moves to a higher part of the hill. Temperatures continue steadily downwards towards their nightly minimum. Everything looks normal until Mahaha's equivalent of about three in the morning: the dead underbelly of the night.

Then, in all of a few seconds, the wind spikes to a jaw-dropping two hundred kilometers an hour, and half the graphs go dead. The remaining ones last just long enough to register slightly increased humidity and temperature, before also ending without a peep. Liu takes the tablet back and pulls up a spreadsheet where she's compiled all the last breaths of the probes we've lost. She shows me the screen again.

An eerie chill crawls up my spine at the display she's put together. The lines of the same graphs from different probes lie stacked on top of one another like so many sleeping bags in a too-small tent. Every last one of the sixteen, in some way or another, matches the end of the Isoptera's data. Some register wind—though nothing like that mega-gust—while others peter out in temperature and humidity conditions I already know match the inside of a cold, white drift. All the probes we've found again were buried in snow or ice.

Buried just like the last team that came here.

More than unpreparedness sank that team. If they were only unprepared, the Isoptera would have survived, not gone belly-up with half its instruments wrecked and the other half frozen. Nor can I hope anymore that Mahaha has grown apart from Jenu's erratic and inexplicable weather since the last Mahaha mission. By the Jenu-marked datasheets among Liu's other tabs, she's come to the same conclusion, and the surge of anxiety it and the graphs give me threatens to rob me of my appetite before I've even touched breakfast. I battle to think straight about next steps.

"What do you think?" I say. Liu might be inexperienced, but she's still our resident meteorologist. I need her smarts on this.

She looks down at the tablet in her hands. "We need to find the probe," she says at last. She points to the thorn-sharp spike of wind that slew the Isoptera. "We need to see what that was."