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 shivered 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."
They were standing on the surface of Mars, bareheaded. Breathing the air with the aid of nothing more than a filter mask. The air was thin, Nadia judged, but she did not feel lightheaded. The high percentage of oxygen was making up for the low atmospheric pressure. It was the partial pressure of oxygen that counted, and so with the percentage of oxygen in the atmosphere so high....
Zeyk said, "Is this is the first time anyone"s done this?"
"No," Sax said. "We did it a lot in Da Vinci."
"It feels good! It"s not as cold as I thought it would be!"
"And if you walk hard," Sax said, "you"ll warm up."
They walked around a bit, careful of their footing in the dark. It was quite cold, no matter what Zeyk said. "We should go back in," Nadia said.
"You should stay out and see the dawn," Sax said. "It"s nice without helmets."
Nadia, surprised to hear such a sentiment coming from him, said, "We can see other dawns. Right now we have a lot to talk about. Besides, it"s cold."
"It feels good," Sax said. "Look, there"s Kerguelen cabbage. And sandwort." He kneeled, brushed a hairy leaf aside to show them a hidden white flower, barely visible in the predawn light.
Nadia stared at him.
"Come on in," she said.
So they went back.
They took their masks off inside the lock, and then they were back in the refuge"s changing room, rubbing their eyes and blowing into their gloved hands. "It wasn"t so cold!" "The air tasted sweet!"
Nadia pulled off her gloves and felt her nose. The flesh was chilled, but it was not the white cold of incipient frostbite. She looked at Sax, whose eyes were gleaming with a wild expression, very unlike him- a strange and somehow moving sight. They all looked excited for that matter, stuffed to the edge of laughter with a peculiar exhilaration, edged by the dangerous situation down the slope in Burroughs. "I"ve been trying to get the oxygen levels up for years," Sax was saying to n.a.z.ik and Spencer and Steve.
Spencer said, "I thought that was to get your fire in Kasei Vallis to burn hard."
"Oh no. As far as fire goes, once you"ve got a certain amount of oxygen, it"s more a matter of aridity and what materials there are to burn. No, this was to get the partial pressure of oxygen up, so that people and animals could breathe it. If only the carbon dioxide were reduced."
"So have you made animal masks?"
They laughed and went up to the refuge commons, and Zeyk set about making coffee while they talked over the walk, and touched each other on the cheek to compare coldnesses.
"What about getting people out of the city?" Nadia said to Sax suddenly. "What if security keeps the gates closed?"
"Cut the tent," he said. "We should anyway, to get people out faster. But I don"t think they"ll keep the gates closed."
"They"re going out to the s.p.a.ceport," someone shouted from the comm room. "The security forces are taking the subway out to the s.p.a.ceport. They"re abandoning ship, the b.a.s.t.a.r.ds. And Michel says the train station- South Station has been wrecked!"
This caused a clamor. Through it Nadia said to Sax, "Let"s tell Hunt Mesa the plan, and get down there and meet the masks."
Sax nodded.
Between Mangalavid and the wristpads they were able to make a very rapid dispersal of the plan to the population of Burroughs, while driving down in a big caravan from Du Martheray to a low line of hillocks just southwest of the city. Soon after their arrival, the two planes bringing the CO2 masks from Da Vinci swooped down over Syrtis, and landed on a swept area of the plains just outside the western ap.r.o.n of the tent wall. On the other side of the city observers on top of Double Decker b.u.t.te had already reported sighting the flood, coming in from a bit north of east: dark brown ice-flecked water, pouring down the low crease that inside the city wall was occupied by Ca.n.a.l Park. And the news about South Station had proved true; the piste equipment had been wrecked, by an explosion in the linear induction generator. No one knew for sure who had done it, but it was done, the trains immobilized.
So as Zeyk"s Arabs drove the boxes of masks to West, Southwest, and South gates, there were huge crowds already congregating inside each of them, everyone dressed either in walkers with heating filaments, or in the heaviest clothes they had- none too heavy for the job at hand, Nadia judged as she went in Southwest Gate, and pa.s.sed out facemasks from boxes. These days many people in Burroughs went out on the surface so seldom that they rented walkers to do so. But there were not enough walkers to dress everyone, and they had to go with people"s interior coats, which were fairly lightweight, and usually deficient in headgear. The message about the evacuation had been sent out with a warning to dress for 255adeg;K, however, and so most people were layered in several garments, appearing thick-limbed and thick-torsoed.
Each gate lock could pa.s.s five hundred people every five minutes- they were big locks- but with thousands of people waiting inside, and the crowds growing as Sat.u.r.day morning wore on, it was not anywhere near fast enough. The masks had been distributed through the crowds, and it seemed certain to Nadia that at this point everyone had one. It was unlikely that anyone in the city was unaware of the emergency. And so she went around to Zeyk, and Sax, and Maya and Michel, and all the other people she knew that she saw, saying, "We should cut the tent wall and just walk out. I"m going to cut the tent wall now." And no one disagreed.
Finally Nirgal showed up, gliding through the crowd like Mercury on an urgent errand, smiling hugely and greeting acquaintance after acquaintance, people who wanted to hug him or shake his hand or just touch him. "I"m going to cut the tent wall now," Nadia told him. "Everyone has masks, and we need to get out of here faster than the gates will let us."
"Good idea," he said. "Let me just announce what"s happening."
And he jumped three meters into the air, grabbing a coping on the gate"s concrete arch and hauling himself up so that he was balanced on it, both feet on the same three-centimeter strip. He turned on a small shoulder loudspeaker he was wearing, and said, "Attention, please!- We"re going to start cutting the tent wall, right above the coping- there should be a breeze outward, not very strong- after that, people nearest the wall out first, of course- there will be no need to hurry at that point- we"ll cut extensively, and everyone should be out of the city in the following half hour. Be ready for the cold- it will be very invigorating very invigorating. Please get your masks on, and check your seal, and the seal of the people around you."
He looked down at Nadia, who had gotten a little laser welder out of her black backpack, and now showed it to Nirgal, holding it overhead so that much of the crowd could see it.
"Is everyone ready?" Nirgal asked over his loudspeaker. Everyone visible in the crowd had a white mask over their lower faces. "You look like bandits," Nirgal told them, and laughed. "Okay!" he said, looking down at Nadia.
And she cut the tent.
Sensible survival behavior is almost as contagious as panic, and the evacuation was quick and orderly. Nadia cut about two hundred meters of tenting, right above the concrete coping, and the higher air pressure inside caused an outflowing wind that held the transparent layers of the tent fabric up and out from the coping, so that people could climb over the waist-high wall without having to deal with it. Others cut the tent near West and South gates, and in about the time it takes to empty a big stadium, the population of Burroughs was out of the city, and into the cold fresh air of an Isidis morning: pressure 350 millibars, temperature 261K, or -12 Celsius.
Zeyk"s Arabs stayed in their rovers and served as escorts, rolling back and forth and guiding people up to the line of hillocks a few kilometers to the southwest of the city, called the Moeris Hills. Floodwater reached the eastern side of the city as the last part of the crowd made it onto this line of low b.u.mps in the plain, and Red observers, ranging wide in rovers of their own, reported that the flood was now running north and south around the foot of the city wall, in a surge that at this point was less than a meter deep.
So it had been a very, very close thing; close enough to make Nadia shudder. She stood on the top of one of the Moeris hillocks, looking about trying to gauge the situation. People had done their best, but were insufficiently dressed, she thought; not everyone had insulated boots, and very few people had much in the way of headgear. The Arabs were leaning out of their rovers to show people how to wrap scarves or towels or extra jackets over their heads in improvised burnoose hoods, and that would have to do. But it was cold out, very cold despite the sun and the lack of wind, and the citizens of Burroughs who did not work on the surface were looking shocked. Although some were in better shape than others; Nadia could spot Russian newcomers by their warm hats, brought from home; she greeted these people in Russian, and almost always they grinned-"This is nothing," they shouted, "this is good ice-skating weather, da da?" "Keep moving," Nadia said to them and to everyone else. "Keep moving." It was supposed to warm up in the afternoon, perhaps up to freezing.
Inside the doomed city the mesas stood stark and dramatic in the morning light, like a t.i.tanic museum of cathedrals, the banks of windows inlaid in them like jewels, the foliage on the mesa tops little green gardens capping the redrock. The city"s population stood on the plain, masked like bandits or hay fever victims, bundled thickly in clothes, some in slim heated walkers, a few carrying helmets for use later if needed; the whole pilgrimage standing and looking back at the city: people on the surface of Mars, their faces exposed to the frigid thin air, standing hands in their pockets, above them high cirrus clouds like metal shavings plastered against the dark pink sky. The strangeness of the sight was both exhilarating and terrifying, and Nadia walked up and down the line of k.n.o.bs talking with Zeyk, Sax, Nirgal, Jackie, Art. She even sent another message to Ann, hoping that Ann was receiving them, even though she never answered: "Make sure the security troops have no trouble at the s.p.a.ceport," she said, unable to keep the anger out of her voice. "Keep out of their way."
About ten minutes later her wrist beeped. "I know," Ann"s voice said curtly. And that was all.
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 pa.s.sing. He was pa.s.sing 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 ma.s.s 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 pa.s.sing 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.
A convention was being established whereby ravines to the east of the piste were being used as latrines. They were getting far enough upslope that people often stopped to look back down into the strangely empty city, with its new moat of dark rusty ice-choked water. Groups of natives were chanting bits of the aerophany as they walked, and hearing it, Nadia"s heart squeezed inside her; she muttered, "Come back out, d.a.m.n you, Hiroko, please- come back out today today."
She spotted Art, and walked over to his side. He was making a running commentary over the wrist, apparently sending it to a news consortium on Earth. "Oh yes," he said in a quick aside when Nadia asked him about it. "We"re live. Real good vid too, I"m sure. And they can relate to the flood scenario."
No doubt. The city with its mesas, surrounded now by black ice-choked water, which was steaming faintly, its surface turbulent, its edges bubbling madly with carbonation, as waves surged down from the north, the noise like waves in a high storm.... The air temperature was now just above freezing, and the surging water was staying liquid even when it pooled and went still, even when it was covered with floating brash ice. Nadia had never seen anything that brought home to her more strongly the fact that they had transformed the atmosphere- not the plants, nor the bluing of the sky color, nor even their ability to expose their eyes, and breathe through thin masks. The sight of water freezing during the Marineris deluge- going from black to white in twenty seconds or less- had marked her more deeply than she knew. Now they had open water. The low broad crease holding Burroughs looked like a gargantuan Bay of Fundy, with the tide racing up it.