by Greg Egan
She moved aside to let Ivo run through his equipment checks. Ada watched the process with an expression of contained disapproval, though Carla suspected that what she most resented was Tamara ignoring her advice. Ada had prepared herself to lead the mission, to bear the final responsibility for everything they did. However much she’d rejoiced to learn that her friend was alive after all, it must have been difficult to relinquish that commanding role.
Tamara told Ivo, “I want you to limit yourself to the powderstone outcrop. Trying to get samples anywhere else will be too difficult; that one mineral will have to serve as a surrogate for all of them.”
“I can live with that,” he replied. He was testing the recoil balance for his air blades, hovering beside one of the remaining guide ropes, proving that he could maintain a fixed separation from it even as he waved the invisible cutting jets about. “Whatever’s responsible for that ultraviolet line looks like the strongest reaction in every case. So if we can quantify the energy release for powderstone—”
Ada said, “What’s wrong with your right arm?”
“Nothing.” Ivo shut off the cutting jets and held up the accused arm for inspection. “Why would you even—?”
“You’re favoring the left one,” Ada said flatly.
“That’s not true,” he protested. “This is a whole new limb! Since I re-extruded it there’s been no pain at all.”
Tamara said, “Hold onto the rope and give the Mite some spin around a vertical axis, using your right hand.”
Ivo buzzed, offended. “Why would I ever need to do that? If I need to adjust the orientation, that’s what the air jets are for.”
“I know,” Tamara said quietly. “I just want to see how strong that arm is.”
Ivo gripped the rope beside him as she’d asked, and reached for the edge of the Mite with his right hand. He managed to get it spinning, but his struggle to ignore the pain was obvious now.
Carla understood: the flesh from his battered right arm hadn’t recovered, because he hadn’t actually managed to resorb it. He had gone through the motions of drawing it into his torso and making it appear that he was extruding an entirely new limb, but the injury had kept the damaged tissue stuck at its original site.
Ada said, “You can’t go out there with an injury.”
Caught out in his deception, Ivo had no reply. Carla couldn’t help feeling some relief that he had been spared the risk of the excursion—but Ada seemed altogether too pleased with the outcome. Ada had had the chance to revel in her own skills, as no navigator had for generations; why should Ivo be cheated of the same kind of fulfillment? What satisfaction was there in tossing sand at the Object, watching the fireworks, then running away? He was a chemist, and he’d come here to do chemistry: he needed to get as close to dirtying his hands as possible, without actually going up in flames in the process.
Carla heard herself saying, “I’ll go with him. I’ll be his right hand.”
“There’s no provision for two operators in the mission plan,” Ada replied, as if that settled it.
“I know how to use the Mite,” Carla said, stubbornness winning out over fear. “If Ivo had had to stay behind for some reason, I’d be the one charged with doing his job. But with a mild injury like this… he’s got too much experience to be replaced. We can add a second harness to the Mite, go out together, and I’ll be there to back him up if he needs it.”
Ada turned to Tamara, scowling. “You can’t possibly countenance this!”
Tamara said, “Ivo?”
“We can make it work,” he said, glancing at Carla with an expression of newfound respect. “I’m sure we can.”
“Let’s just try some rehearsals first,” Tamara said cautiously. “Each of you operating the Mite up here in orbit, with the other in harness as a passenger. If you strike any problems, the whole thing is off.”
“Of course,” Carla agreed. “That sounds fair.” She could feel her whole body growing charged with excitement, even as the voice of prudence in her head began howling in disbelief.
Ivo reached over and placed his palm against Carla’s, their skin making contact through the small apertures they’d cut into the cooling bags.
Ready? he wrote.
As I’ll ever be, Carla replied.
She glanced up at the Gnat, a dozen strides above them; Ada and Tamara were looking out through the window, their forms visible in the starlight but their faces impossible to read.
Carla rested the exposed fingertips of her lower right hand against the dials of the clock on the underside of the Mite, and wriggled a little to make herself more comfortable. She and Ivo were harnessed to a long flat plate that ran beside the main structure, held apart from it by six narrow struts. Struts and plate alike were hollow, and covered in fine holes; just as air flowed out through the fabric of her cooling bag, every part of the Mite was leaking, sending a thin breeze wafting out into the void in the hope of warding off danger. For all the sense this made, Carla still felt almost comically exposed—as if a solid hull like the Gnat’s might have offered them greater protection.
Ivo reached down and opened the valve on the air jet to his left. In itself, the kick of acceleration was barely noticeable; Carla merely felt as if one side of her harness had been drawn a little tighter. But when she looked up again the Gnat was receding—outpacing them in its orbit now, as the blast of air acted as a gentle brake on the Mite.
Ivo shut off the jet. They were separating from the Gnat so slowly that Carla could imagine Tamara stepping out through the hatch onto a fanciful sky-road, catching up with them effortlessly and handing them some item they’d neglected to pack. As for their rate of descent, that was too slight to discern at all. But the tiny reduction in their orbital velocity had reshaped their trajectory from a circle into an ellipse; in six bells, their altitude would be less by a factor of ten.
The whole flight plan they’d prepared relied on the assumption that the usual principles of celestial mechanics would keep working in the Object’s environs. Given the spectacular failure of traditional chemistry Carla wasn’t willing to take anything for granted, but all the evidence so far was that the orthogonal rock beneath them was producing the same kind of gravitational field as a comparable body made from ordinary matter. From the Gnat’s orbital period Tamara had estimated the Object’s total mass, and her figure was consistent with the kind of minerals Ivo’s spectra had identified on the surface. Rock couldn’t magically change into something entirely new just because you encountered it at a different angle in four-space. Indeed, one faction among the chemists maintained that ordinary matter ought to contain both positive and negative luxagens—in equal numbers, symmetrically arranged—and that the swapped rock in the Object would thus be literally identical to ordinary rock. Carla had had some sympathy for the notion on purely esthetic grounds—and it certainly would have made Silvano happy if it had turned out to be true—but the fate of Ivo’s projectiles had demolished that idea.
Comfortable? Ivo asked her.
She turned to him. Sure. Ivo looked composed, as far as she could judge from the sight of his face through his helmet. If all went well, for the next six bells they’d have nothing to do but watch the stars and the scenery. All the danger would be down on the surface—and the trick to staying sane until then was to accept that they couldn’t speed up their descent and get the whole thing over any sooner.
Carla gazed down at the gray plain directly below the Mite; though they were leaving this region behind, it was precisely where their spiral journey would finally deposit them. The craters here were wider and more numerous than elsewhere on the surface, bolstering the hope that the gray rock really would turn out to be as soft as powderstone.
As the plain slipped away she tried to imagine the collisions that had left these craters. The strange reaction with ordinary matter was probably not to blame; they looked too much like Pio’s craters, the product of nothing but like crashing into like at planetary speeds. The astronomers
believed that the Object had started out deep within the orthogonal cluster a dozen light years away, then spent eons drifting alone through the void. Once, though, it must have been part of something larger.
What had torn that mother world apart? Perhaps a wildfire deep within it. A wildfire ignited how? By the tiny probability for every luxagen in every rock to break free from its energy valley—with the chance of escape mounting up over cosmic time. Some solids would be resilient, succumbing to nothing more than an inevitable slow corrosion, but others would suffer a kind of avalanche, with the change at one site shrinking the gaps between the energy levels for its neighbors, accelerating the process.
In the end, everything in the cosmos wanted to make light and blow itself to pieces. The only thing that differed was the time scale, set by the number of photons required to make the leap from solidity to chaos. But if the luxagens in most kinds of rock needed to make six or seven photons at a time in order to decay—six or seven far-infrared photons, each with the highest possible energy—what could possibly shrink that gap down to the single ultraviolet photon that Ivo’s spectra had revealed?
Carla’s gut tightened. She hadn’t been hungry since the journey began, but she found herself longing for the comforting aroma of groundnuts.
Other hands feeling steady? she asked Ivo.
Very, he assured her.
She wanted to see this reaction close up; the more she pondered the mystery, the more she ached to understand it. She just didn’t want to end up partaking in it herself.
Gyroscopes kept the Mite’s orientation locked against the stars, so as its orbit carried it around the Object, the Object in turn moved across the sky. Carla hardly needed to check the clock to know when they’d made half a revolution: the terrain that now stretched out above her head, its wide horizon upside down but level, rendered the whole configuration obvious.
It was her side of the Mite that was leading now, so it was her turn to brake the vehicle. She opened her air jet, counting the flickers beneath her fingertips, delivering a blast a little longer than Ivo’s. Their new orbit would be much rounder than the last one, but still sufficiently elliptical for its closest approach to bring them almost to the surface. Skimming above the powderstone plains, they could choose the most promising site and then kill their velocity entirely. Once they had fallen to within arm’s reach of the surface, resisting any further motion would require only the gentlest vertical thrust.
The ceiling of rock began tipping down toward Ivo’s side of the Mite, their descent propelling them around the Object ever faster. Carla found the sense of momentum more empowering than alarming; she’d had enough of waiting. She wanted to see a plain of orthogonal matter spread out beneath her, near enough to touch. This fragment of the primal world had traveled backward around the history of the cosmos; the world that had given birth to her ancestors had taken the opposite course. For a child of one to encounter the other would close that vast, magnificent loop—and the meeting that the Hurtlers offered with violence could here be made serene. With caution, serene.
Ivo took her hand. Did you see that?
What?
The flash, he replied.
Carla looked past him at the jagged brown rock, unchanging in the starlight. Perhaps the Object collided with specks of ordinary dust now and then. It was even possible that some fleck of material from the hull of the Gnat, or a particle of unburnt sunstone from their final burn, had just made its way to the surface.
She saw the next flash herself. It was less fierce than the ones they’d provoked from the Gnat, and much more diffuse—less a blazing pinprick than a brilliant daub of light. An ignition as dispersed as that wasn’t due to a fleck of anything.
What’s doing this? she asked Ivo. He didn’t have time to reply before the surface lit up again, a burst of blue-tinged flame spreading out across the rock, then quickly dissipating.
Us? he suggested.
Carla felt her muscles grow tense with fear, but his theory made no sense. How could they still be shedding anything, after the air had flowed over them for so long? Any loose material in their equipment or on their bodies should have been carried away into the void long ago by the relentless breeze.
What, exactly? she replied.
Ivo thought for a lapse or two, while another flash erupted on his left.
Contaminant in the air, he concluded.
Carla couldn’t see his face, which was turned toward the Object, but his posture was hunched in shame. Ivo had been responsible for filtering all the air they’d packed, ensuring that it contained no particulate matter. She couldn’t imagine him treating the task with anything but scrupulous attention.
But he wasn’t taking the blame for no reason; the symptoms lent his verdict a horrible plausibility. If the Mite’s would-be air shield was actually spraying traces of fine dust in all directions, that would explain why these ignitions were so much more dispersed than the ones brought on by the projectiles.
The flashes were coming every pause or two now, and the wall of rock was drawing closer. Carla struggled not to panic; the single worst thing they could do would be to aim an air jet straight at the surface in the hope of a swift ascent. All their tanks had to be treated as equally suspect: the contents of any of them touching the surface could engulf the Mite in a conflagration.
She made some quick calculations on her thigh. Jet four, six flickers, she suggested. Jet four was pointing back along their orbit; though the burst of air would be aimed horizontally, it would raise their velocity and reduce the curvature of their trajectory enough to cause them to ascend.
What about spillage? Ivo protested.
Can’t be helped. The jet’s nozzle would send out a wide spray, some of which was sure to reach the surface. But if they did nothing they’d remain on their original orbit, passing within a few dozen strides of the rock. The flames were probably reaching at least that high already, and with the source of contamination even closer the eruptions could only become more intense.
Shut off all air? Ivo replied.
Carla hesitated. Would that be wiser than risking the jet? The air shield was clearly more of a liability than a source of protection, but she couldn’t say the same about their cooling bags.
Hyperthermia? she countered.
Shield is worst thing, Ivo pointed out. Bags later, not for long.
He didn’t wait for a reply for the first step; he reached into the center of the Mite and closed the outlet valve on the air tank feeding the shield.
The blue flares persisted, undiminished, for so long that Carla came close to proclaiming that Ivo’s dismal hypothesis was wrong, and that they could use the air jet to retreat with impunity. Then, abruptly, the rock became dark.
Once it had actually happened, it was hard to think of this respite from the encroaching flames as a bad thing. But the fact that Ivo had been right about the cause didn’t mean his minimal air scenario really was the Mite’s best chance. If they did use the jet, how much spillage would there be? How high would the explosion reach? Would it spread out from the ignition site fast enough to catch them?
The truth was, Carla didn’t know. She couldn’t quantify any of these things.
How long, then, could they survive without air drawing heat from their bodies? People who’d lived through accidents in the void rarely had a chance to consult a clock, but Carla had heard claims that the limit was a couple of chimes.
The Object filled half the sky. Her irresolution had settled the matter: they were too close now to risk using the jet. All they could do was follow the orbit down.
Carla could see the plains of gray powderstone approaching, below her to the left but swinging toward her right, the wall of rock tilting and coming full circle. The scale was impossible to judge; she checked the clock. The lowest point on the orbit was still seven chimes away.
A wide, shallow crater slid by, its ancient walls broken like the ruined desert fortress her father had described to her as he recited a stor
y from the sagas. As it passed, flames erupted along part of its rim and spilt across the ground. This was it: the meeting of worlds she’d longed for. With a pang of grief she thought of sweet Carlo, fighting so hard to keep her alive, poring over census records to plan their every meeting.
A trail of blue fire pursued the Mite, streaking across the pitted landscape. The light from it was dazzling, almost painful, but Carla couldn’t look away. Ivo reached up to the tank on his chest and shut off the air to his cooling bag. Moments later the flames subsided, but they did not die completely.
She squeezed Ivo’s hand, lost for words but trying to let him know that she didn’t blame him. He hadn’t forced her to join him. The ground was so close now that Carla could see the structure of the rock, the surface of coarse lumps and concavities about the size of her fist. It looked exactly like powderstone. Ivo’s bold plan to grab a sample here might even have worked, if not for the blunder that had rendered his air blades as suicidal as any hardstone chisel.
The flames were rising again, and gaining on the Mite. Carla checked the clock; the low point was still four chimes away. She turned down her cooling air as far as she could while still sensing some flow across her skin, but the effect on the height of the flames was slight, and soon overtaken by the Mite’s descent. She could feel the heat coming off the blazing ground now, worse than anything her own body could inflict on her.
She shut off the air completely.
The flames faltered, then winked out, leaving the Mite gliding over the starlit landscape. Carla felt a rush of euphoria, but time and geometry were not on her side. Once she and Ivo had both lost consciousness, their deaths would be guaranteed. Even if they were still alive at the point where it was safe to turn on the air again, they’d be oblivious to the chance to save themselves.
