The walking pipeline’s nozzle was pointing their way. And then, with a faint seismic roar, the last complete ridge was overwhelmed. A rush of dark water ran up the rock, and then poured down the western side of the ridge in a waterfall some hundred meters wide. It fell the two hundred meters of its descent in a slow lazy sheet. In the context of the great ice world stretching to the horizon in every direction, it was no more than a trickle — but it kept pouring steadily, the water on the eastern mass now channelized by ice on its sides, the falls booming like thunder, the water on the western side fanning out in a hundred streams through the broken ice — and the hair on Maya’s neck lifted in fear. Probably a memory of the Marineris flood, she decided, but couldn’t say for sure.

Slowly the volume of the waterfall decreased, and in less than an hour it had all slowed and then frozen, at least on the surface; though a sunny fall day, it was eighteen degrees below freezing down there, and a line of ragged cumulonimbus clouds was approaching from the west, indicating a cold front. So the waterfall eventually stilled. But left behind was a fresh icefall, coating the rock ridge with a thousand smooth white tubes. So now the ridge had become two promontories which did not quite meet, like all the other ridges of the Zea Dorsa, all diving into the ice like sets of matching ribs: matching peninsulas. The Hellas Sea was continuous now, and Minus One truly an island.

After that, the circumHellas train trips and the various overflights felt different to Maya, as she perceived the interlaced network of glaciers and ice chaoses in the basin to be the new sea itself, rising and filling and sloshing around. And in fact the liquid sea under the surface ice near Low Point was growing much faster in the springs and summers than it was shrinking in the autumns and winters. And strong winds kicked up waves in the polynyas, which in the summers broke the ice between them, creating regions of brash ice, a floating pack of ice chunks which growled so loudly as they rode the steep little swells that conversation in dirigibles overhead was difficult.

And in the year M-49, the flow rates from all the tapped aquifers reached their maximums, combining to pump 2,500 cubic meters a day into the sea, an amount that would fill the basin to the  — 1-kilometer contour in about six M-years. To Maya this did not seem long at all, especially as they could see the progress, right there on Odessa’s horizon. In winters the black storms that poured over the mountains would blanket the whole basin floor with startling white snow; in the springs the snow would melt, but the new edge of the ice sea would be closer than it had been the previous autumn.

It was much the same in the northern hemisphere, as news reports and her infrequent trips to Burroughs made clear. The great northern dunes of Vastitas Borealis were being rapidly inundated, as the truly enormous aquifers under Vastitas and the north polar region were being pumped onto the surface by drilling platforms that rose on the ice as the ice accumulated under them. In the northern summers, great rivers were pouring off the melting northern polar cap, cutting channels through the laminate sands and running down to join the ice. And a few months after Minus One had been islanded, news reports showed video of an uncovered stretch of ground in Vastitas, disappearing under a dark flood from west and east and north. This apparently created the last link between the lobes of ice; so now there was a world-wrapping sea in the north. Of course it was patchy still, and covered only about half of the land between the sixtieth and seventieth latitudes, but as satellite photos showed, there were already great bays of ice extending south into the deep depressions of Chryse and Isidis.

Submerging the rest of Vastitas would take about twenty more M-years, as the amount of water necessary to fill Vastitas Borealis was much greater than that needed to fill Hellas. But the pumping operation up there was bigger as well, so things were proceeding apace, and all the acts of Red sabotage combined could do no more than put a dent in this progress. In fact progress was accelerating despite increasing acts of sabotage and ecotage, because some of the new mining methods being put into use were quite radical, and very effective. The news programs showed video of the latest method, which set off big underground thermonuclear explosions, very deep under Vastitas. This melted the permafrost over large areas, providing the pumps with more water. On the surface these explosions were manifested as sudden icequakes, which reduced the surface ice overhead to a bubbling slurry, the liquid water soon freezing on the surface, but tending to stay liquid underneath. Similar explosions under the northern polar cap were causing floods nearly as vast as the great outbursts of “61. And all that water was pouring downhill into Vastitas.

Down at the office in Odessa, they followed all of this with professional interest. A recent assessment of the amount of underground water in the north had encouraged the Vastitas engineers to shoot for a final sea level very near the datum itself, the 0-kilometer contour that had been set back in the days of sky areology. Diana and other hydrologists in Deep Waters thought that subsidence of the land in Vastitas, as a result of the mining of aquifers and permafrost, would cause them to end up with a sea level somewhat lower than the datum. But up there they seemed confident they had factored that in, and would reach the mark.

Fooling around with various sea levels on an office AI map made it clear what shape the coming ocean was likely to have. In many places the Great Escarpment would form its southern shoreline. Sometimes that would mean a gentle slope; in the fretted terrain, archipelagos; in certain regions, dramatic seaside cliffs. Broached craters would provide good harbors. The Elysium massif would become an island continent, and the remains of the northern polar cap would as well — the land under the cap was the only part of the north well above the 0-kilometer contour.

No matter which exact sea level they chose to display on the maps, a big southern arm of the ocean was going to cover Isidis Planitia, which was lower than most of Vastitas. And aquifers in the highlands around Isidis were being pumped down into it as well. So a big bay was going to fill the old plain, and because of that, construction crews were building a long dike in an arc around Burroughs. The city was located fairly close to the Great Escarpment, but its elevation was just below the datum. It was therefore going to become a port city every bit as much as Odessa, a port city on a world-wrapping ocean.

The dike they were building around Burroughs was two hundred meters high and three hundred meters wide. Maya found the concept of a dike to protect the city disturbing, though it was clear from the aerial shots taken of it that it was another pharaonic monument, tall and massive. It ran in a horseshoe shape, with both its ends up on the slope of the Great Escarpment, and it was so big that there were plans to build on it, to make it into a fashionable Lido district, containing small boat harbors on its water side. But Maya remembered once standing on a dike in Holland, with the land on one side of her lower than the North Sea on the other side of her; it had been a very disorienting sensation, more unbalancing than weightlessness. And, on a more rational level, as news programs from Earth now showed, all dikes there were currently stressed by a very slight rise in sea level, caused by global warming initiated two centuries before. As little as a meter’s rise endangered many of the low-lying areas of Earth, and Mars’s northern ocean was supposed to rise in the coming decade by a full kilometer. Who could say whether they would be able to fine-tune its ultimate level so accurately as to make a dike sufficient? Maya’s work in Odessa made her worry about such control, though of course they were trying for it themselves in Hellas, and thought that they probably had it. They had better, as Odessa’s location gave them little margin for error. But the hydrologists also talked about using the “canal” that had been burned by the aerial lens before its destruction, as a runoff into the northern ocean, if such a runoff became necessary. Fine for them, but the northern ocean would have no such recourse.