by Rich Horton
Two meters below the surface hung a metal sphere with three projecting rods. In her youth, whenever she became tired, Eunice could swim up to this power unit and draw as much energy from it as she needed. Back then, she had taken it for granted, but in these days of weary scavenging, it seemed incredible. Three hexapods could recharge there at any one time, and her other sisters usually floated a short distance away, like fish drawn to crusts of bread in a pond.
Eunice had once asked how it worked. She had been talking to James at the harbor, as she often did, her dome barely visible above the water. James had been seated with his console on the yacht, dressed in the red windbreaker that he wore so that the twelve hexapods could know who he was. Her sense of facial recognition was limited, and the face above his collar was nothing to her but a brown blur.
James typed his response. It was not her native language, and it had to pass through several stages of translation before taking a form that she could understand. “We call it depth cycling—the water gets cooler the deeper you go. The cylinder rises to the warm water and sinks to the cold. When it moves, it generates electricity, and the power goes to the charging station.”
Eunice didn’t entirely understand this explanation, but she accepted it. She had spent most of her short life alternately rising and falling, and it was enough to know that the cylinder on the tether did the same. “I see.”
It was a seemingly inconsequential exchange, but when she looked back, she saw that it had marked the moment at which James had taken an interest in her. Eunice had been the only hexapod to ask such questions, and she suspected that this was why she had been one of the five who had been chosen to leave home. Until the end, no one knew who would be going. They were all powered down, and when she awoke, she found that they had already arrived at the survey site.
As soon as she was lowered into the ocean, she felt the difference. Sampling the water, she was overwhelmed by unfamiliar scents and tastes, and she realized only belatedly that James was speaking to her. “Are you ready?”
Eunice turned her attention toward the research vessel, where she immediately picked out the red windbreaker. “I think so.”
“You’ll do fine,” James said. His words rang clearly in her head. “Good luck.”
“Thank you,” Eunice said politely. Her sisters were bobbing on the swell around her. A flicker of light passed between them, and then Thetis descended, followed by Clio and Dione. Galatea looked at Eunice for a moment longer, but instead of speaking, she disappeared as well.
Eunice opened her lower tank, allowing water to flow inside, and drifted down with the others. As the ocean surrounded her, her radio went dead, and she switched to her acoustic sensors, which registered an occasional chirp from the yacht overhead. At this depth, the water was still bright, and she could see the other four hexapods spreading out below her in a ring.
At two hundred meters, they switched on their lamps, which lit up like a wreath of holiday lights. It took forty minutes to reach their destination. As the water around her grew milky, her sensors indicated that the level of sulfides had increased. A second later, a strange landscape condensed out of the shadows, and Thetis, who had been the first to arrive, blinked a message. “I’m here.”
Eunice slowed. Her surroundings became more distinct, and she saw that they had reached the hydrothermal vent. Within her sphere of light, the water was cloudy and very blue, and she could make out the looming pillars and misshapen rings formed by lava flows. Heaps of white clams, some nearly a foot long, lay wedged in the crevices, along with crabs, mussels, shrimp, and the hedges of tube worms, which were rooted like sticks of chalk with tips as red as blood.
At the vent itself, where heated water issued up from the crust, a central fissure was flanked by older terrain to either side. The hexapods promptly identified a promising base of operations, but it was left to Thetis, their designated leader, to confirm the decision. “We’ll start here.”
As soon as she had spoken, Eunice felt Wagner, who had been clinging unnoticed to her midsection, silently free himself. The other toroids detached from the four remaining hexapods, distributing themselves evenly around the vent, and began to crawl imperceptibly across the sand.
Eunice spent the next two days exploring. Each sister had a designated assignment—mapping the terrain, conducting sediment analysis, performing chemical observations—and her own brief was to prepare a detailed census of the ecosystem. Everything was recorded for analysis on the surface, and she quickly became entranced by her work. Around the cones of the black smokers, which released clouds of boiling fluid, pink worms crept in and out of their honeycombs, and the broken fragments of spires sparkled on the inside with crystals.
In the meantime, the toroids continued their labors, and after fifty hours, their efforts were rewarded. Under ordinary conditions, each of the five hexapods could work at full capacity under her own power for approximately three days before returning to a charging station. Every such trip represented a loss of valuable time, and after taking into consideration the conditions under which they would be operating, their designers had arrived at an elegant alternative.
The solution was based on the nature of the vent itself, where the dissolved sulfides issuing from the crust provided a source of energy that could thrive in the dark, as bacteria converted hydrogen sulfide into the sugars and amino acids that formed the basis of a complex food web. It was the only way that life could exist under such harsh conditions, and it was also what would allow the hexapods to carry out their duties over the weeks and months to come.
When Eunice felt her power fading, she went to Wagner. The toroids were no more than a few meters from where she had left them, although she knew that they had been systematically farming the sediment the entire time. As they inched along, they sucked up free sulfides, which served as a substrate for the microbial fuel cells—filled with genetically modified versions of the same chemosynthetic bacteria found here in abundance—that were stacked in rings inside their bodies.
Eunice positioned herself above the toroids and signaled to Wagner, who slipped up and around her middle. As the rest of the hexapods did the same, she felt a surge of energy. It was a practical method of recharging in the field, but she soon found that it also left her with a greater sense of kinship to the life that she was studying, which relied on the same principles to survive.
The cycle of renewal gave shape to their days, which otherwise were spent in work. Once a week, a hexapod would go up to transmit the data that they had collected. There was no other practical way to communicate, and these visits amounted to their only link with home.
On the third week, it was Eunice’s turn. After ascending alone for nearly an hour, following an acoustic signal, she surfaced. The yacht was holding station exactly where it was supposed to be, and as she swam toward it, she heard a familiar voice in her head. “How are you doing?”
A scoop net lifted her onto the deck. As Eunice rose in a gentle curve, feeling slightly disoriented from the unaccustomed movement, she tried to seem nonchalant. Her lights flashed. “Happy to be here.”
The net was handled by a deckhand whose clothes she didn’t recognize. He deposited her into a tank on the boat, and once she had righted herself, she saw James seated nearby. She could tell without counting that there were fewer people in sight than there had been on her arrival—the human crew spent the week onshore, returning to the rendezvous point only to pick up the latest set of observations. Aside from James, none of them ever spoke to her.
As Eunice wirelessly shared the data, she kept one line of thought fixed on her friend. “Are you pleased with our work?”
After receiving the question on his console, James entered a reply. “Very pleased.”
Eunice was happy to hear this. Her thoughts had rarely been far from home—she wouldn’t see the charging station or the seven sisters she had left behind until after the survey was complete—but she also wanted to do well. James had entrusted her with a
crucial role, and it had only been toward the end of her training that she had grasped its true importance.
A month earlier, after a test run in the harbor, Eunice had asked James why they were studying the vent at all. His response, which she had pieced together over the course of several exchanges, had done little to clarify the situation. “There are metals in the sulfide deposit. They precipitate there over time. Some people think that they’re worth money. Even if they aren’t, we’ll have to go after them eventually. We’ve used up almost everything on land. Now we have to turn to the water.”
Eunice had tried to process this, although fully half of it was meaningless. “And me?”
James had typed back. “If we want to minimize our impact on the life at the vent, we need to know what we’re trying to save. You’re going to tell us what lives there. Not everyone cares about this, but there are regulations that they need to follow. And I’ll take the funding where I can get it.”
Eunice had understood this last part fairly well. Funding, she knew, was another form of energy, and without it, you would die. But this had left another question unanswered. “So what do you really want me to do?”
James had responded without hesitation. “You’re going where I can’t. These vents are special. They may even have been where life began—they’re chemically rich, thermally active, and protected from events on the surface. The ocean is a buffer. A refuge. This is our best chance to study what might be there. And—”
He had paused. “And it could end at any moment. There are people here who want to start mining right away. If they can convince the others to take their side, they might do it. Your work may keep us from destroying what we don’t understand. That’s what I want from you.”
Other questions had naturally arisen in her mind, but James had seemed distracted, so she had held off. Seeing him again now at the survey site reminded her of the exchange, and she resumed her work with a renewed sense of purpose. She had always been aware of the beauty of the vent, but now she grew more conscious of its fragility. Perhaps, she thought, she might even play a role in saving it.
And then everything changed. One day, Dione came down from a scheduled data delivery, long before they had expected her to return, to share some disturbing news. “There was no yacht.”
The others all stopped what they were doing. Thetis’s lights flashed. “You’re sure?”
“I followed protocol,” Dione said. “There were no signals on the way up and nothing on the radio.”
After an intensive discussion, which lasted for nearly ten seconds, they decided that there was no cause for concern, since they had been trained against the possibility that the yacht might occasionally be delayed. Their orders were to continue working as if nothing had changed, and if they received no signals in the meantime, to check in again at the appointed hour.
A week later, Clio went up to find that there was still no one there. Seven days later, the lot fell to Eunice. On reaching the surface, she saw nothing but the empty ocean, and when she switched on her radio, she found that all frequencies were silent. Her range was very short, but it confirmed that there was nothing transmitting within several kilometers of their position.
Eunice sank down again. On her return trip, she found herself brooding over what James had said. He had seemed concerned that they wouldn’t be able to continue the project for long, and although it seemed unthinkable that the five of them would simply be abandoned here, the idea weighed enough on her mind that she felt obliged to speak to one of her sisters.
She chose Galatea, with whom she was the closest, but when they withdrew to a distant part of the vent field, her sister seemed unconvinced. “I don’t know what else we can do. We can’t leave. You’ve seen the map.”
Eunice knew what she meant. They depended on a steady supply of hydrogen sulfide. Without it, they would lose power within three days, and if they left this energy source, there was no guarantee that they would find another. The known vents were an average of a hundred kilometers apart, and they could travel no more than thirty without recharging. “We have to do something.”
“But we are. We’re following our instructions. That’s enough for now.” Galatea had turned and swum away. Eunice had remained where she was for another minute, trying to convince herself that her sister was right, and she had finally returned to work. She had continued her observations, ignoring her growing uneasiness, and she might have stayed there forever until—
A transmission from Wagner broke through this cycle of memories. “Ready?”
Eunice stirred. It took her a second to remember where she was. Checking herself, she found that she was anchored at the center of a whale fall, far from that first vent, her life with her sisters a fading dream. She had been in stasis for eighty hours, all of which her toroid had spent recharging itself.
Wagner was waiting for her response. It was a formality, but there was also one point that she hadn’t shared with her companion. This whale fall lay at the exact midpoint of her journey. It was still possible to backtrack, retracing her steps to the original vent, carried by the current instead of fighting it. Until now, she had closed her mind to this possibility, focusing instead on the way forward, and she knew that if they went on from here, there would be no turning back.
But she had really made her choice long ago. She roused herself. “We’ll leave now.”
Eunice pulled out of the sand and positioned herself above Wagner, who slid securely into place. She felt energy flow into her, as she had hundreds of times before, and tried to draw courage from it. Then she rose, leaving the latest whale fall behind. It was just another stepping stone. Since leaving her sisters at the East Pacific Rise, off the coast of Mexico, she had traveled alone for two thousand kilometers, and she was halfway home to Seattle.
• • •
II.
Eunice moved through the darkness with her lights off, her sensors searching for sulfides in the water. Even after countless such excursions, it was never less than frightening. The hardest part was leaving the oasis of a whale fall, where she knew that she could at least rest in safety. She had been trained to protect her own existence, not to take risks, and whenever she embarked on the next step forward, she had to overcome all of her natural instincts for caution.
As she swam, she constantly updated her position relative to the last whale fall, which was currently ten kilometers behind her. She was experienced and careful, but within the overall route that she was following, the distribution of the falls was perfectly random. Eunice had only one chance to get it right, and she had learned long ago that intelligence was far less important than persistence and luck.
She checked her coordinates against the chart in her head. Compared to the organisms that drifted naturally from one fall to another, she had several advantages. She possessed a map with the locations of all documented hydrothermal vents, and she could navigate by dead reckoning, which was the only system that worked reliably in the bathyal zone. It was vulnerable to integration drift—its accuracy tended to degrade as errors accumulated over time—and she had to recalibrate whenever she reached a landmark, but so far, it had served her well.
According to her map, the next vent lay fifty kilometers to the north, but she wouldn’t know for sure until she arrived. A vent could vanish after a few years or decades, and she had occasionally reached her intended destination only to find nothing there. Even if the information was accurate, there was no way to get to the nearest vent without pausing several times to recharge. Given her effective range of thirty kilometers, she could safely travel half that distance before reversing course, which meant that she had to find a whale fall somewhere within that fixed circle.
But the existence of the next fall—and all the ones after that—was solely a matter of probability, which meant that she had to be perfect every time. By now, she had refined her approach. Whenever she found a new whale fall, after recharging, she would ascend to the surface to check for radio transmissio
ns. After savoring the light for a moment, she would descend again, embarking in the general direction of the next confirmed vent to the north. She would cover close to fifteen kilometers, which was the limit of her range in any one direction, and then shift laterally by one kilometer to return by a slightly different course.
Like Wagner, she had to methodically cover a defined area, but on a far greater scale. Her sensors could pick up sulfides from a distance of five hundred meters, which coincided with the working range of her sonar. The calculation was simple. There were approximately twenty possible paths that she could take while remaining within her intended line of travel, and she had to shuttle along them systematically until she found the next whale fall in the series.
To get home, she had to do this successfully over three hundred times. The resulting path, which she recorded in her head, resembled a series of scallop shells, each one joined at a single point to those before and after. So far, she had always found a fall eventually, although there had been occasions when she had been forced to backtrack—all twenty of the possible paths had led nowhere, so she retreated another step, to the whale fall before the last, to trace an entirely new route. It was tedious, but she had considerable reserves of patience.
At the moment, she was thirteen kilometers into her fifth excursion from her most recent whale fall, which meant that she would have to turn back soon. No matter how often she went on these sorties, departing from a known refuge was always a test of nerve. Because her lights could draw predators, she kept them off, trusting to her sensors and navigation system. She might have increased her range by traveling at a zone of lower pressure, but she had to stay within a few hundred meters of the seabed to pick up whatever might be there, so she moved in the darkness.
For a system that was so unforgiving of error, it was also grindingly monotonous, and she was left for hours at a time with her thoughts. Eunice spent part of every journey reviewing her data for patterns in the distribution of the falls, but this consumed just a fraction of her processing power. She had been designed to observe and analyze, and in isolation, her mind naturally turned on itself. It was the most convenient subject at hand, and even her makers, who had only a general idea of her inner life, might not have understood where it would lead.
