Now that they were out of the city, Maya was feeling buoyant. “Let’s start walking,” she cried. “It’s a long way to Libya Station, and half the day is almost gone already!”

“True,” Nadia said. And many people had already started, heading over to the piste that ran out of Burroughs South Station, and following it south, up the slope of the Great Escarpment.

• • •

So they walked away from the city. Nadia often stopped to encourage people, and so quite often she was looking back at Burroughs, at the rooftops and gardens under the transparent bubble of the tent, in the midday sunlight— down into that green mesocosm that for so long had been the capital of their world. Now rusty black ice-flecked water had run almost all the way around the city wall, and a thick flow of dirty icebergs was coming down from the low crease to the northeast, pouring toward the city in a broadening torrent, filling the air with a roar that raised the hair on the back of her neck, a Marineris rumbling. . . .

The land they walked over was dotted by scattered low plants, mostly tundra moss and alpine flowers, with occasional stands of ice cactus like spiky black fire hydrants. Midges and flies, disturbed by the strange invasion, whirred around in the air overhead. It was noticeably warmer than it had been in the morning, the temperatures rising fast; it felt a little above zero. “Two seventy-two!” Nirgal cried when Nadia asked him in passing. He was passing by every few minutes, running up and down the crowd from one end of the line to the other and back again. Nadia checked her wrist: 272°. The wind was very slight, and from the southwest. The weather reports indicated the high-pressure zone would stay over Isidis for another day at least.

People were walking in small knots, in the process of finding other small knots, so that friends and work groups and acquaintances were greeting each other as they moved along, surprised often by familiar voices under masks, familiar eyes between mask and hood or hat. A diffuse frost cloud rose from the crowd, a mass exhalation, burning off quickly in the sun. Rovers from the Red army had driven up from both sides of the city, hurrying to get away from the flood; now they moved along slowly, their outriders passing out flasks of hot drinks. Nadia glared at them, mouthing silent curses inside the privacy of her mask, but one of the Reds saw the curse in her eyes, and said to her irritably, “It wasn’t us broke the dike, you know, it was the Marsfirst guerrillas. It was Kasei!”

And he drove on.