The air learned the game before Ivo understood he was playing one.
He pulsed light through the analysis chamber: twice, pause, once. The suspended structures gathered against the glass and broke apart in the same rhythm. He changed the sequence. They followed.
Electrostatic response, he wrote in the maintenance log. Then, while he was changing a sensor, they gave him a sequence he hadn't used. He watched the recording three times.
Outside the habitat window, a low valley lay beneath pale clouds. Nothing walked there. Nothing grew taller than the dark crust along the rocks. They had searched for life on the ground for six months.
The ship called.
"Ground clearance in forty minutes. How's the air?"
Ivo looked at the chamber.
"Still testing."
"Your daughter's asking whether she'll need the mask indoors."
"She won't."
He had promised that before he knew what the test was showing.
The chamber admitted a continuous stream of outside air. Under magnification, the suspended structures resembled branching splinters. They joined briefly, separated, then joined elsewhere. Their arrangements survived changes in the current by passing from one group to another.
He pulsed their new sequence back. The splinters held still. Then they changed it again, adding a long interval.
He made a mistake repeating it. The chamber flashed the original sequence, waited, and flashed it once more.
Ivo laughed inside his respirator. "All right."
This time he got it right.
The splinters gathered at the side nearest his face.
He turned their light fluctuations into sound. Five wavering notes came from the console. Across the chamber, a second grouping answered with a different pattern.
He didn't know whether these were greetings, arguments or requests for him to stop. The first group kept returning to its five notes between exchanges. He began thinking of them as a name.
He tried to take a sample. The chamber had a removable vessel for contaminants. He diverted some of the current into it and closed the valve.
The branching structures remained visible, drifting harmlessly inside. He played the notes. Nothing answered.
When he reopened the vessel to the outside flow, the structures joined the passing air and the response resumed. He tried a larger vessel, with its own circulating current.
Again, silence.
Whatever was speaking extended through the currents outside. He could bottle its pieces. He couldn't make them speak alone.
The ship called a second time.
"We need your decision shortly. If the site isn't viable, we recover you and take the return window."
"Understood."
Behind the caller he heard a child arguing about whose turn it was to sit by a screen.
There were three hundred people aboard. Ivo had seen their names on the sleeping assignments. His wife had marked their family's compartment with a square of yellow cloth so their daughter could find it.
On Earth, they'd rented a bedroom beside a freight tunnel. Every morning the first train shook black grit from the window frame. His daughter had drawn a garden on the wall. When they left, the landlord deducted the cost of painting it over.
Here she'd asked for a room where she could leave the window open.
Ivo brought up the purifier's first trial, run that morning.
Before treatment, the air in the test channel had contained the same branching structures. He'd filed their changing arrangements as turbulence. Watching now, he could distinguish a short pattern repeating whenever the sensor lamp blinked.
After treatment, the particles remained chemically intact, but their branches had separated.
He opened the retained treated sample to the live current. The damaged structures drifted through the others without joining them. The chamber's response faltered around the gap.
He increased the magnification, although there was nothing further he needed to see.
The purifier made the atmosphere safe by breaking the bonds that let the particles assemble inside human lungs. It broke those same bonds in the open air.
He played the morning's pattern through the console.
The living formations repeated it once, then went back to their own exchange.
He saved the recording under a new filename.
The five notes came again from the chamber. On the authorization screen, he could select BIOLOGICAL HOLD. The ship would turn back. There was a report field in which he could put everything he'd found.
He opened it.
Outside, clouds passed over the valley. He had no idea how far the connected formations extended, how many there were, or whether the moving shadows meant anything to them.
The treatment system would clear the settlement basin. Its intake towers were already drawing the surrounding air toward the habitat.
"Ivo?"
His wife this time.
"Is it safe for her to sleep there?"
He looked at the empty report field.
"Give me a minute."
The chamber began the game again. Twice, pause, once.
He put his hand against the glass.
Then he closed the report and authorized treatment.
The console accepted his signature. Outside, the intake towers changed pitch.
The chamber flashed.
Ivo answered the sequence.
It came back with an interval missing.
He repeated the whole thing, slowly, as though he could help it remember.
The splinters tried to gather. Some found each other and held for a moment. The five notes broke into isolated tones.
By the time the ship entered the atmosphere, the chamber contained an even drift of particles.
The first families came through the habitat lock at dusk.
Ivo's daughter ran to him wearing the respirator she'd decorated with small silver fish. He knelt and loosened the straps. They had left shallow red lines beside her nose.
She breathed cautiously, then took a deeper breath.
"It smells nice."
The treatment left a faint mineral sweetness. He'd noticed it in the first sample.
She leaned against him, her bare face warm beneath his chin.
"What's that smell?"
He touched one of the marks the mask had left.
"Can you breathe all right?"
