Indeed, as they drove uphill great waves of dark cloud rolled in from the northwest, pouring over them as if chasing the fell-runners. Sax shuddered, remembering his recent exposure to the elements; he was happy to be in a rover, and felt he would need only short walks away from it to be satisfied.

Eventually, however, they stopped on a high point in a low old ridge, and got out. They made their way over a surface littered with boulders and knobs, cracks, sand drifts, very small craters, breadloafed bedrock, scarps and alases, and the old shallow channels that gave the dissected unit its name. In truth there were deformational features of every kind to be seen, for the land here was four billion years old. A lot had happened to it, but nothing had ever happened to destroy it completely and clean the slate, so all four billion years were still there to be seen, in a veritable museum of rockscapes. It had been thoroughly pulverized in the Noachian, leaving regolith several kilometers deep, and craters and deformities that no aeolian stripping could remove. And during this early period the other side of the planet had had its lithosphere to a depth of six kilometers blasted into space by the so-called Big Hit; a fair amount of that ejecta had eventually landed in the south. That was the explanation for the Great Escarpment, and the lack of ancient highlands in the north; and one more factor in the extremely disordered look of this land.

Then also, at the end of the Hesperian had come the brief warm wet period, when water had occasionally run on the surface. These days most areologists thought that this period had been quite wet but not really very warm, annual averages of well under 273° Kelvin still allowing for surface water sometimes, replenished by hydrothermal convection rather than precipitation. This period had lasted for only a hundred million years or so, according to current estimates, and it had been followed by billions of years of winds, in the arid cold Amazonian Age, which had lasted right up to the point of their arrival. “Is there a name for the age starting with m-1?” Sax asked.

“The Holocene.”

And then lastly, everything had been scoured by two billion years of ceaseless wind, scoured so hard that the older craters were completely rimless, everything stripped at by the relentless winds strata by strata, leaving behind a wilderness of rock. Not chaos, technically speaking, but wild, speaking its unimaginable age in polyglot profusion, in rimless craters and etched mesas, dips, hummocks, escarpments, and oh so many blocky pitted rocks.

Often they stopped the rover and walked around. Even small mesas seemed to tower over them. Sax found himself staying near their rover, but nevertheless he came upon all kinds of interesting features. Once he discovered a rover-shaped rock, cracked vertically all the way through. To the left of the block, off to the west, he had a view to a distant horizon, the rocky land out there a smooth yellow glaze. To the right, the waist-high wall of some old fault, pocked as if by cuneiform. Then a sand drift bordered by ankle-high rocks, some of them pyramidal dark basaltic ventifacts, others lighter pitted granulated rocks. There a balanced shat-tercone, big as any dolmen. There a sand tail. There a crude circle of ejecta, like an almost completely weathered Sto-nehenge. There a deep snake-shaped hollow — the fragment of a watercourse, perhaps — behind it another gentle rise — then a distant prominence like a lion’s head. The prominence next to it was like the lion’s body.

In the midst of all this stone and sand, plant life was unobtrusive. At least at first. One had to look for it, to pay close attention to color, above all else to green, green in all its shades, but especially its desert shades — sage, olive, khaki, and so on. Nanao and Tariki kept pointing out specimens he hadn’t seen. Closer he looked, and closer again. Once attuned to the pale living colors, which blended so well with the ferric land, they began to jump out from the rust and brown and umber and ocher and black of the rock-scape. Hollows and cracks were likely places to see them, and near the shaded patches of snow. The ctoser he looked, the more he saw; and then, in one high basin, it seemed there were plants tucked everywhere. In that moment he understood; it was all fellfield, the whole Tyrrhena massif.

Then, coating entire rockfaces, or covering the inside areas of drip catchments, were the dayglow greens of certain lichens, and the emerald or dark velvet greens of the mosses. Wet fur.

The diversicolored palette of the lichen array; the dark green of pine needles. Bunched sprays of Hokkaido pines, foxtail pines, Sierra junipers. Life’s colors. It was somewhat like walking from one great roofless room to another, over ruined walls of stone. A small plaza; a kind of winding gallery; a vast ballroom; a number of tiny interlocked chambers; a sitting room. Some rooms held krummholz bansei against their low walls, the trees no higher than their nooks, gnarled by wind, cut along the top at the snow level. Each branch, each plant, each open room, as shaped as any bonsai — and yet effortless.

Actually, Nanao told him, most of the basins were intensively cultivated. “This basin was planted by Abraham.” Each little region was the responsibility of a certain gardener or gardening group.

“Ah!” Sax said. “And fertilized, then?”

Tariki laughed. “In a manner of speaking. The soil itself has been imported, for the most part.”

“I see.”

This explained the diversity of plants. A little bit of cultivation, he knew, had been done around Arena Glacier, where he had first encountered the fellfields. But here they had gone far beyond those early steps. Labs in Sabishii, Tariki told him, were trying their best to manufacture topsoil. A good idea; soil in fellfields appeared naturally at a rate of only a few centimeters a century. But there were reasons for this, and manufacturing soil was proving to be extremely difficult.

Still, “We pick up a few million years at the start,” Nanao said. “Evolve from there.” They hand-planted many of their specimens, it seemed, then for the most part left them to their fate, and watched what developed.

“I see,” Sax said.

He looked more closely yet. The clear dim light: it was true that each great open room displayed a slightly different array of species. “These are gardens, then.”

“Yes … or things like that. Depends.”

Some of the gardeners, Nanao said, worked according to the precepts of Muso Soseki, others according to other Japanese Zen masters; others still to Fu Hsi, the legendary inventor of the Chinese system of geomancy called feng shui; others to Persian gardening gurus, including Omar Khayyam; or to Leopold or Jackson, or other early American ecologists, like the nearly forgotten biologist Oskar Schnell-ing; and so on.

These were influences only, Tariki added. As they did the work, they developed visions of their own. They followed the inclination of the land, as they saw that some plants prospered, and others died. Coevolution, a kind of epigenetic development.

“Nice,” Sax said, looking around. For the adepts, the walk from Sabishii up onto the massif must have been an aesthetic journey, filled with allusions and subtle variants of tradition that were invisible to him. Hiroko would have called it areoformation, or the areophany. “I’d like to visit your soil labs.”

“Of course.”

They returned to the rover, drove on. Late in the day, under dark threatening clouds, they came to the very top of the massif, which turned out to be a kind of broad undulating moor. Small ravines were filled with pine needles, sheered off by winds so that they looked like the blades of grass on a well-mowed yard. Sax and Tariki and Nanao again got out of the car, walked around. The wind cut through their suits, and the late-afternoon sun broke out from under the dark cloud cover, casting their shadows all the way out to the horizon. Up here on the moors there were many big masses of smooth bare bedrock; looking around, the landscape had the red primal look Sax remembered from the earliest years; but then they would walk to the edge of a small ravine, and suddenly be looking down into green.