Part 42 (1/2)

Sax squinted. ”I don't think so. Depends on how big the gap is.”

”Can we set counterexplosions and close the gap?”

”I don't think so. Look, here's video sent from some Reds south of the break on the dike.” He pointed at a screen, which displayed an IR image with black to the left and blackish green to the right, and a forest-green spill across the middle. ”That's the blast zone there in the middle, warmer than the regolith. The explosion appears to have been set next to a pod of liquid water. Or else there was an explosion set to liquefy the ice behind the break. Anyway, that's a lot of water coming through. And that will widen the break. No, we've got a problem.”

”Sax,” she exclaimed, and held on to his shoulder as she stared at the screen. ”The people in Burroughs, what are they supposed to do? G.o.d d.a.m.n it, what could Ann be thinking thinking?”

”It might not have been Ann.”

”Ann or any of the Reds!”

”They were attacked. It could have been an accident. Or someone on the dike must have thought they were going to get forced away from the explosives. In which case it was a use-it-or-lose-it situation.” He shook his head. ”Those are always bad.”

”d.a.m.n them.” Nadia shook her head hard, trying to clear it. ”We have to do something!” She thought frantically. ”Are the mesa tops high enough to stay above the flood?” them.” Nadia shook her head hard, trying to clear it. ”We have to do something!” She thought frantically. ”Are the mesa tops high enough to stay above the flood?”

”For a while. But Burroughs is at about the lowest point in that little depression. That's why it was sited there. Because the sides of the bowl gave it long horizons. No. The mesa tops will get covered too. I can't be sure how long it will take, because I'm not sure of the flow rate. But let's see, the volume to be filled is about...” He tapped away madly, but his eyes were blank, and suddenly Nadia saw that there was another part of his mind doing the calculation faster than the AI, a gestalt envisioning of the situation, staring at infinity, shaking his head back and forth like a blind man. ”It could be pretty fast,” he whispered before he was done typing. ”If the melt pod is big enough.”

”We have to a.s.sume it is.”

He nodded.

They sat there beside each other, staring at Sax's AI.

Sax said hesitantly, ”When I was working in Da Vinci, I tried to think out the possible scenarios. The shapes of things to come. You know? And I worried that something like this might happen. Broken cities. Tents, I thought it would be. Or fires.”

”Yes?” Nadia said, looking at him.

”I thought of an experiment- a plan plan.”

”Tell me,” Nadia said evenly.

But Sax was reading what looked like a weather update, which had just appeared over the figures scrolling on his screen. Nadia patiently waited him out, and when he looked up from his AI again, she said, ”Well?”

”There's a high-pressure cell, coming down Syrtis from Xanthe. It should be here today. Tomorrow. On Isidis Planitia the air pressure will be about three hundred and forty millibars, with roughly forty-five percent nitrogen, forty percent oxygen, and fifteen percent carbon diox-”

”Sax, I don't care about the weather!”

”It's breathable,” he said. He eyed her with that reptile expression of his, like a lizard or a dragon, or some cold posthuman creature, fit to inhabit the vacuum. ”Almost breathable. If you filter the CO2. And we can do that. We manufactured face-masks in Da Vinci. They're made from a zirconium alloy lattice. It's simple. CO2 molecules are bigger than oxygen or nitrogen molecules, so we made a molecular sieve filter. It's an active filter too, in that there's a piezoelectric layer, and the charge generated when the material bends during inhalation and exhalation- powers an active transfer of oxygen through the filter.”

”What about dust?” Nadia said.

”It's a set of filters, graded by size. First it stops dust, then fines, then CO2.” He looked up at Nadia. ”I just thought people might- need to get out of a city. So we made half a million of them. Strap the masks on. The edges are sticky polymer, they stick to skin. Then breathe the open air. Very simple.”

”So we evacuate Burroughs.”

”I don't see any alternative. We can't get that many people out by train or air fast enough. But we can walk.”

”But walk to where?”

”To Libya Station.”

”Sax, it's about seventy k from Burroughs to Libya Station, isn't it?”

”Seventy-three kilometers.”

”That's a h.e.l.l of a long way to walk!”

”I think most people could manage it if they had to,” he said. ”And those who can't could be picked up by rovers or dirigibles. Then as people get to Libya Station, they can leave by train. Or dirigible. And the station will hold maybe twenty thousand at a time. If you jam them in.”

Nadia thought about it, looking down at Sax's expressionless face. ”Where are these masks?”

”They're back at Da Vinci. But they're already stowed in fast planes, and we could get them here in a couple hours.”

”Are you sure they work?”

Sax nodded. ”We tried them. And I brought a few along. I can show you.” He got up and went to his old black bag, opened it, pulled out a stack of white facemasks. He gave Nadia one. It was a mouth-and-nose mask, and looked very much like a conventional dust mask used in construction, only thicker, and with a rim that was sticky to the touch.

Nadia inspected it, put it over her head, tightened the thin strap. She could breathe through it as easily as through a dust mask. No sensation of obstruction at all. The seal seemed good.

”I want to try it outside,” she said.

First Sax sent word to Da Vinci to fly the masks over, and then they went down to the refuge lock. Word of the plan and the trial had gotten around, and all the masks Sax had brought were quickly spoken for. Going out along with Nadia and Sax were about ten other people, including Zeyk, and n.a.z.ik, and Spencer Jackson, who had arrived at Du Martheray about an hour before.

They all wore the current styles of surface walker, which were jumpsuits made of layered insulated fabrics, including heating filaments, but without any of the old constrictive material that had been needed in the early low-pressure years. ”Try leaving your walker heaters off,” Nadia told the others. ”That way we can see what the cold feels like if you're wearing city clothes.”

They put the masks over their faces, and went into the garage lock. The air in it got very cold very fast. And then the outer door opened.

They walked out onto the surface.

It was cold. The shock of it hit Nadia in the forehead, and the eyes. It was hard not to gasp a little. Going from 500 millibars to 340 would no doubt account for that. Her eyes were running, her nose as well. She breathed out, breathed in. Her lungs ached with the cold. Her eyes were right out in the wind- that was the sensation that most struck her, the exposure of her eyes. She s.h.i.+vered as the cold penetrated her walker's fabrics, and the inside of her chest. The chill had a Siberian edge to it, she thought. 260adeg;K,-13 Centigrade- not that bad, really. She just wasn't used to it. Her hands and feet had gotten chilled many a time on Mars, but it had been years and years- over a century in fact!- since her head and lungs had felt the cold like this.

The others were talking loudly to each other, their voices sounding funny in the open air. No helmet intercoms! Her walker's neckring, where the helmet ought to have rested, was extremely cold on her collarbones and the back of her neck. The ancient broken black rock of the Great Escarpment was covered with a thin night frost. She had peripheral vision such as she never had in a helmet- wind- tears running down her cheeks from the cold. She felt no particular emotion. She was surprised by how things looked un.o.bstructed by a faceplate or any other window; they had a sharp-edged hallucinatory clarity, even in starlight. The sky in the east was a rich predawn Prussian blue, with high cirrus clouds already catching the light, like pink mares' tails. The ragged corrugations of the Great Escarpment were gray-on-black in the starlight, lined with black shadows. The wind in her eyes!

People were talking without intercoms, their voices thin and disembodied, their mouths hidden by the masks. There was no mechanical hum, buzz, hiss, or whoosh; after over a century of such noise, the windy silence of the outdoors was strange, a kind of aural hollowness. n.a.z.ik looked like she was wearing a Bedouin veil.

”It's cold,” she said to Nadia. ”My ears are burning. I can feel the wind on my eyes. On my face.”

”How long will the filters last?” Nadia said to Sax, speaking loudly to be sure she was heard.

”A hundred hours.”

”Too bad people have to breath out through them.” That would add a lot more CO2 to the filter.

”Yes. But I couldn't see a simple way around it.”