Sax trailed behind, looking off at the basin below them.
• • •
The next day they climbed back in the Three Diamonds and took to the air again and floated southeast, until the captain dropped an anchor line just to the west of the Zea Dorsa. It had been quite a while since Maya had driven out onto them with Diana and her friends, and now the ridges were no more than skinny rock peninsulas, extending out into the shattered ice toward Minus One, and diving under the ice one after the next— all except for the largest one, which was still an unbroken ridge, dividing two rough ice masses, the western ice mass clearly about two hundred meters lower than the eastern one. This, Diana said, was the final line of land connecting Minus One and the basin rim. When this isthmus was overwhelmed, the central rise would be an actual island.
The ice mass on the eastern side of the remaining dorsum was at one point very near to the ridgeline. The dirigible captain let out more anchor line and they floated east on the prevailing wind until they were directly over the ridge, where they could see clearly that only meters of rock remained to be overcome. And off to the east was a walking pipeline, a blue hose sliding slowly back and forth on its ski pylons as its nozzle shot water onto the surface. Under the drone of the props, they could hear occasional creaks and moans from below, a muffled boom, a high crack like a gunshot. There was liquid water below the ice, Diana explained, and the weight of new water on top was causing some sections of ice to scrape over barely submerged dorsa. The captain pointed to the south, and Maya saw a line of icebergs fly into the air as if propelled by explosives, arcing in various directions and falling back onto the ice, breaking into thousands of pieces. “Maybe we’d better back off a little,” the captain said. “It would be better for my reputation if we did not get shot out of the sky by an iceberg.”
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.