But something in him made him keep trying. “Look, Ann, I’m an advocate of what people call the minimum viable model. It’s a model that calls for a breathable atmosphere only up to about the two- or three-kilometer contour. Above that the air would be kept too thin for humans, and there wouldn’t be much life of any kind — some high-altitude plants, and above that nothing, or nothing visible. The vertical relief on Mars is so extreme that there can be vast regions that will remain above the bulk of the atmosphere. It’s a plan that makes sense to me. It expresses a comprehensible set of values.”

She did not reply. It was distressing, it really was. Once, in an attempt to understand Ann, to be able to talk to her, he had done research in the philosophy of science. He had read a fair amount of material, concentrating particularly on the land ethic, and the fact-value interface. Alas, it had never proved to be of much help; in conversation with her, he had never seemed able to apply what he had learned in any useful manner. Now, looking down at her, feeling the ache in his joints, he recalled something that Kuhn had written about Priestley — that a scientist who continued to resist after his whole profession had been converted to a new paradigm might be perfectly logical and reasonable, but had ipso facto ceased to be a scientist. It seemed that something like this had happened to Ann, but what then was she now? A counterrevolutionary? A prophet?

She certainly looked like a prophet — harsh, gaunt, angry, unforgiving. She would never change, and she would never forgive him. And all that he would have liked to say to her, about Mars, about Gamete, about Peter — about Simon’s death, which seemed . to haunt Ursula more than her … all that was impossible. This was why he had more than once resolved to give up talking to Ann: it was so frustrating never to get anywhere, to be faced with the dislike of someone he had known for over sixty years. He won every argument but never got anywhere. Some people were like that; but that didn’t make it any less distressing. In fact it was quite remarkable how much physiological discomfort could be generated by a merely emotional response.

Ann left with Desmond the next day. Soon after that Sax got a ride north with Peter, in one of the small stealthed planes that Peter used to fly all over Mars.

Peter’s route to Burroughs led them over the Hellespontus Monies, and Sax gazed down into the big basin of Hellas curiously. They caught a glimpse of the edge of the icefield that had covered Low Point, a white mass on the dark night surface, but Low Point itself stayed over the horizon. That was too bad, as Sax was curious to see what had happened over the Low Point mohole. It had been thirteen kilometers deep when the flood had filled it, and that deep it was likely that the water had remained liquid at the bottom, and probably warm enough to rise quite a distance; it was possible that the icefield was in that region an ice-covered sea, with telltale differences at the surface.

But Peter would not change his route to get a better view. “You can look into it when you’re Stephen Lindholm,” he said with a grin. “You can make it part of your work for Biotique.”

And so they flew on. And the next night they landed in the broken hills south of Isidis, still on the high side of the Great Escarpment. Sax then walked to a tunnel entrance, and went down into the tunnel and followed it into the back of a closet in the service basement of Libya Station, which was a little train station complex at the intersection of the Burroughs-Hellas piste and the newly rerouted Burroughs-Elysium piste. When the next train to Burroughs came in, Sax emerged from a service door and joined the crowd getting on the train. He rode into Burroughs’ main station, where he was met by a man from Biotique. And then he was Stephen Lindholm, newcomer to Burroughs and to Mars.

The man from Biotique, a personnel secretary, complimented him on his skillful walking, and took him to a studio apartment high in Hunt Mesa, near the center of the old town. The labs and offices of Biotique were also in Hunt, just under the mesa’s plateau, with window walls looking down on the canal park. A high-rent district, as only befitted the company leading the terraforming project’s bioengineering efforts.

Out the Biotique office’s windows he could see most of the old city, looking about the same as he remembered it, except that the mesa walls were even more extensively lined by glass windows, colorful horizontal bands of copper or gold or metallic green or blue, as if the mesas were stratified by some truly wonderful mineral layers. Also the tents that had topped the mesas were gone, their buildings now standing free under the much larger tent that now covered all nine mesas, and everything in between and around them. Tenting technology had reached the point where they could enclose vast mesocosms, and Sax had heard that one of the trans-nats was going to cover Hebes Chasma, a project that Ann had once suggested as an alternative to terraforming — a suggestion that Sax himself had scoffed at. And now they were doing it. One should never underestimate the potential of materials science, that was clear.

Burroughs’ old canal park, and the broad grass boulevards that climbed away from the park and between the mesas, were now strips of green, cutting through orange tile rooftops. The old double row of salt columns still stood beside the blue canal. There had    i been a lot of building, to be sure; but the configuration of the city was still the same. It was only on the outskirts that one could see clearly how much things had changed, and how much larger the city really was; the city wall lay well beyond the nine mesas, so that quite a bit of surrounding land was sheltered, and much of it built upon already.

The personnel secretary gave Sax a quick tour of Biotique, making introductions to more people than he could remember. Then Sax was asked to report to his lab the next morning, and given the rest of the day to get settled in.

As Stephen Lindholm he planned to exhibit signs of intellectual energy, sociability, curiosity, and high spirits; and so he very plausibly spent that afternoon exploring Burroughs, wandering from neighborhood to neighborhood. He strolled up and down the wide swards of streetgrass, considering as he did the mysterious phenomenon of the growth of cities. It was a cultural process with no very good physical or biological analogy. He could see no obvious reason why this low end of Isidis Planitia should have become home to the largest city on Mars. None of the original reasons for siting the city here were at all adequate to explain it; so far as he knew, it had begun as an ordinary way station on the piste route from Elysium to Tharsis. Perhaps it was precisely because of its lack of strategic location that it had prospered, for it had been the only major city not damaged or destroyed in 2061, and thus perhaps it simply had had a head start on growth in the postwar years. By analogy to the punctuated equilibrium model of evolution, one might say that this particular species had accidentally survived an impact that had devastated most other species, giving it an open ecosphere to expand in.

And no doubt the bowllike shape of the region, with its archipelago of small mesas, gave it an impressive look as well. When he walked around on the wide grassy boulevards, the nine mesas appeared evenly distributed, and each mesa had a slightly different look, its rugged rock walls distinguished by characteristic knobs, buttresses, smooth walls, overhangs, cracks — and now the horizontal bands of colorful mirror windows, and the buildings and parks on the flat plateaus crowning each mesa. From any point on the streets one could always see several of the mesas, scattered like magnificent neighborhood cathedrals, and this no doubt gave a certain pleasure to the eye. And then if one took an elevator up to one of the mesa’s plateau tops, all about a hundred meters higher than the city floor, then one had a view over the rooftops of several different districts, and a different perspective on the other mesas, and then, beyond those, the land surrounding the city for many kilometers, distances larger than were usual on Mars, because they were at the bottom of a bowl-shaped depression: over the flat plain of Isidis to the north, up the dark rise to Syrtis in the west, and to the south one could see the distant rise of the Great Escarpment itself, standing on the horizon like a Himalaya.