To get a better view Nadia went up to the top floor of the Du Martheray refuge, where an observation window, disguised as a horizontal crack just under the rim, gave a view down the Great Escarpment to the new dike and the ice pressing against it. For a long time she stared down at the sight, sipping coffee mixed with a dose of kava. To the north was the ice sea, with its clustered seracs and long pressure ridges, and the flat white sheets of giant frozen-topped melt lakes. Directly below her lay the first low hills of the Great Escarpment, dotted with spiky expanses of Acheron cacti, sprawling over the rock like coral reefs. Staircased meadows of black-green tundra moss followed the courses of small frozen streams dropping down the Escarpment; the streams in the distance looked like long algae diatoms, tucked into creases in the redrock.

Burroughs Region

And then in the middle distance, dividing desert from ice, ran the new dike, like a raw brown scar, suturing two separate realities together.

Nadia spent a long time studying it through binoculars. Its southern end was a regolith mound, running up the apron of Crater Wg and ending right at Wg’s rim, which was about half a kilometer above the datum, well above the expected sea level. The dike ran northwest from Wg, and from her prospect high on the Escarpment Nadia could see about forty kilometers of it before it disappeared over the horizon, just to the west of Crater Xh. Xh was surrounded by ice almost to its rim, so that its round interior was like an odd red sinkhole. Everywhere else the ice had pressed right up against the dike, for as far as Nadia could see. The desert side of the dike appeared to be some two hundred meters high, although it was difficult to judge, as there was a broad trench underneath the dike. On the other side, the ice bulked quite high, halfway up or more.

The dike was about three hundred meters wide at the top. That much displaced regolith— Nadia whistled respectfully— represented several years of work, by a very large team of robot draglines and canal-diggers. But loose regolith! It seemed to her that huge as the dike was on any human scale, it was still not much to contain an ocean of ice. And ice was the easy part— when it became liquid, the waves and currents would tear regolith away like dirt. And the ice was already melting; immense melt pods were said to lie everywhere underneath the dirty white surface, including directly against the dike, seeping into it.

“Aren’t they’re going to have to replace that whole mound with concrete?” she said to Sax, who had joined her, and was looking through his own binoculars at the sight.