Грег Иган - The Year's Best Science Fiction, Volume 1

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.

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 transmissions. 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.

As Eunice neared the end of her range, her memories returned to the day that she had decided to head off on her own. For months after they had lost contact with the research vessel, the five hexapods had continued their weekly trips to the surface, but there had been no sign of the yacht. At one point, after some discussion, Eunice had volunteered to go up and switch on her emergency beacon, which transmitted a powerful signal for several days on a single charge.

The time alone had given her a chance to think. James had warned her that the project might end at any moment, and if that were the case, then it might only be a matter of time before the next phase of operations began. She knew nothing of how mining at the deposit would proceed, but she had no doubt that it would be destructive. Even if it spared the vent itself, there would be other dangers. And she found that she had no intention of waiting around to find out either way.

After her beacon had faded without drawing any response, Eunice had remained there for another hour before beginning her descent. When she returned, she saw that the others seemed untroubled, although this might have been an illusion in itself. With their sixfold minds, it was hard for the hexapods to settle on a course of action, and the continuum of possible alternatives often seemed to average out to complacency. In reality, this equilibrium was highly unstable, and when a disruption occurred, it could happen with startling speed.

One day, Eunice returned from surveying an area of the vent that she had studied before to find only three sisters at the recharging area. She blinked her lights at the others. “Where’s Thetis?”