He stood again and wandered, mapless over the rock. Some of the deeper hollows contained ice pools. Around midday he descended into one of these and ate his lunch by the ice pool, lifting the air mask to take bites out of a grain-and-honey bar. Elevation 4.5 kilometers above the datum; air pressure 267 millibars. A high-pressure system indeed. The sun was low in the northern sky, a bright dot surrounded by pewter.

The ice of the pool was clear in places, like little windows giving him a view of the black bottom. Elsewhere it was bubbled or cracked, or white with rime. The bank he sat on was a curve of gravel, with patches of brown soil and black dead vegetation lying on it in a miniature berm— the high-water mark of the pond, apparently, a soil shore above the gravel one. The whole beach was no more than four meters long, one wide. The fine gravel was an umber color, piebald umber or. . . . He would have to consult a color chart. But not now.

The soil berm was dotted by pale green rosettes of tiny grass blades. Longer blades stood in clumps here and there. Most of the taller blades were dead, and light gray. Right next to the pond were patches of dark green succulent leaves, dark red at their edges. Where the green shaded into red was a color he couldn’t name, a dark lustrous brown stuffed somehow with both its constituent colors. He would have to call up a color chart soon, it seemed; lately when looking around outdoors he found that a color chart came in handy about once a minute. Waxy almost-white flowers were tucked under some of these bicolored leaves. Farther on lay some tangles, red-stalked, green-needled, like beached seaweed in miniature. Again that intermixture of red and green, right there in nature staring at him.

A distant wind-washed hum; perhaps the harping rocks, perhaps the buzz of insects. Black midges, bees . . . in this air they would only have to sustain about thirty millibars of CO2, because there was so little partial pressure driving it into them, and at some point internal saturation was enough to hold any more out. For mammals that might not work so well. But they might be able to sustain twenty millibars, and with plant life flourishing all over the planet’s lower elevations, CO2 levels might drop to twenty millibars fairly soon; and then they could dispense with the air tanks and the face masks. Set loose animals on Mars.

In the faint hum of the air he seemed to hear their voices, immanent or emergent, coming in the next great surge of viriditas. The hum of distant voices; the wind; the peace of this little pool on its rocky moor; the Nirgalish pleasure he took in the sharp cold. . . . “Ann should see this,” he murmured.

Then again, with the space mirrors gone, presumably everything he saw here was doomed. This was the upper limit of the biosphere, and surely with the loss of light and heat the upper limit would drop, at least temporarily, perhaps for good. He didn’t like that; and it seemed possible there might be ways to compensate for the lost light. After all, the terraforming had been doing quite well before the mirrors’ arrival; they hadn’t been necessary. And it was good not to depend on something so fragile, and better to be rid of it now rather than later, when large animal populations might have died in the setback along with the plants.