Actually, lying on the grass made it clear how much the permafrost was melting. And the melt lay on a hardpan of still-frozen ground, so that the surface became saturated and boggy. When Sax stood up, his ventral side chilled instantly in the breeze. He spread his arms to the sunlight. Photon rain, vibrating across the spin networks. In many regions heat exhaust from nuclear power plants was being directed down into capillary galleries in the permafrost, he told Bao as they walked back to the rover. This was causing trouble in some wet areas, which were tending to saturate at the surface. The land melting, so to speak. Instant wetlands. A very active biome, in fact. Though the Reds objected. But most of the land that would have been affected by permafrost melt was now under the North Sea anyway. What little remained above the sea was to be treasured as swamps and marshes.

The rest of the hydrosphere was almost equally transformative of the surface. It couldn’t be helped; water was a very effective carver of rock, hard though it was to believe when watching a gossamer waterfall drift down a sea cliff, turning to white mist long before it hit the ocean. Then again there was the sight of the massive giant howler waves, battering the cliffs so hard that the ground shook underfoot. A few million years of that and those cliffs would be significantly eroded.

“Have you seen the riverine canyons?” she asked.

“Yes, I saw Nirgal Vallis. Remarkable how satisfying it was to see water down at its bottom. So apt.”

“I didn’t know there was so much tundra out here.”

Tundra was the dominant ecology for much of the southern highlands, he told her. Tundra and desert. In the tundra, fines were fixed very effectively to the ground; no wind could lift mud, or quicksand, of which there was a good quantity, making it dangerous to travel in certain regions. But in the deserts the powerful winds ripped great quantities of dust into the sky, cooling temperatures while they darkened the day, and causing problems where they landed, as they had for Nirgal. Suddenly curious, he said, “Have you ever met Nirgal?”

“No.”

The sandstorms these days were nothing like the long-forgotten Great Storm of course, but still a factor that had to be considered. Desert pavement formed by microbacteria was one very promising solution, though it tended to fix only the top centimeter of deposits, and if the wind tore the edge of the pavement, what was underneath was then free to be borne away. Not an easy problem. Dust storms would be with them for centuries.

Still, an active hydrosphere. Meaning life everywhere.

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