After several minutes, Phoebe finally broke the ice among them. She had her nose pressed to her window. “This is amazing.”

  By now, they had fallen out of the brighter waters into a twilight world. Adam failed to appreciate her sense of wonder. The landscape outside was a featureless wash of dark blue, except for swirls of snow lit by the vehicle’s lamps. He knew the snow was a mix of krill, micro-shrimps, and plankton. Occasionally a curious fish would burst into view, then vanish away. A few jellyfish lingered longer, until the Cormorant fell past their floating bells.

  Soon, twilight became night.

  “We’re exiting the thermocline,” Datuk reported, staring at a colorfully lighted display of data.

  “Which means what?” Monk asked.

  Datuk readjusted his glasses and pointed to a screen. The information glowing there came from the vehicle’s external Niskin water sampler and CTD sensor. The screen ran with a slew of real-time readings: depth, outside pressure, temperature, conductivity, salinity, pH, and oxygen levels.

  “The thermocline lies between the ocean’s sunlit layers and the colder depths,” Datuk explained. “The temperature dropped rapidly when we first descended. But now out of the thermocline, it’ll drop much slower. We’re at four degrees now. It’ll drop only another two or three degrees before we reach the bottom. Ending at just above freezing.”

  Adam looked over Datuk’s shoulder. While the temperature reading on his screen had slowed, the depth and pressure gauges continued to rise. It was the only evidence that they were still descending. Inside the DSV, there was no sense of motion.

  Phoebe was drawn into the conversation, twisting around. “We’re now entering the bathypelagic—or midnight—zone of the ocean. Between one thousand and four thousand meters. After that, we’ll drop into the abyssopelagic zone.”

  Datuk nodded. “And below six thousand meters, we’ll reach the bottommost region of the ocean—the hadal zone—named after Hades, the Greek god of the underworld. These unexplored depths make up nearly half the ocean. Yet, until a short time ago, more people had walked on the moon than had visited these extreme depths. Currently, though, the score stands at twelve on the moon and twenty-two who reached the bottom of the ocean’s deepest trenches.”

  Even in the dim light, Phoebe’s eyes shone with her excitement. “And those numbers are about to change today.”

  Adam wished he could appreciate their enthusiasm. During their safety class, he had learned the two greatest dangers during a descent: a fire or a leak. At these pulverizing depths, there would be no chance of a rescue. Their best defense was early detection.

  As they continued down, Bryan interrupted his movie every fifteen minutes to give their topside monitors an update. Adam listened attentively each time—not so much to the technical details, a majority of which was over his head anyway, but to the tone in their pilot’s voice. Adam strained to hear any note of distress or alarm.

  Still, after another hour, it was hard to maintain that level of concentration and tension. To his surprise, Adam found himself drifting into a light drowse, his eyelids slipping closed.

  Phoebe’s voice—sharp with surprise—stirred him back to full attention. “I think we’re entering a brine layer,” she said.

  Adam sat straighter. Beyond the front window, the black waters were illuminated by the exterior lamps. Only now there was a distinct haziness to the view, as if they were sinking through cloudy chicken broth.

  Datuk spoke up from his station. His eyes were still glued to the screen next to him. “You’re right, Dr. Reed. The salinity spiked eightfold. It’s definitely a dense layer of saltier water.”

  “Is it a reason for concern?” Adam asked, leaning forward.

  “Not for us,” Phoebe said. “But such spots are kill-zones for marine life. Due to the water’s hypersalinity and lack of oxygen.”

  Datuk nodded. “But these brine stratifications host all manner of strange chemosynthetic organisms. Due to their unique enzymes, they’ve been studied for pharmaceutical and industrial uses. Much like the piezophiles that I study.”

  Monk stared at the biochemist. “You mean those organisms that survive under high pressure?”

  “That’s right.” Datuk smiled. “These brine layers also show heightened electrical conductivity. Such a unique property will be used to harvest water from the atmosphere of Mars. Something that the ExoMars lander—the Kazachok—will attempt to demonstrate when it’s sent there in a year or two.”

  Monk turned to Adam, lifting an eyebrow. They had both avoided raising the subject of the scientist’s connection to China’s space agency. If the man was a mole, they didn’t want to spook him. But Datuk had just offered them a perfect opening to broach the subject.

  Besides, where could he go now?

  9:50 P.M.

  As Phoebe studied the murky brine layer, movement in the window’s reflection drew her eye. She noted Adam leaning forward from the rear seat.

  “Dr. Lee,” he said, “you mentioned earlier that your study into high-pressure organisms had interested the space industry. Why?”

  Phoebe had been wondering the same. Intrigued, she twisted around to face the others.

  Datuk grinned, his eyes sparkling. Like most scientists, he was happy to extol about his research. “I’m part of an investigative team called LAB. The Laboratory for Agnostic Biosignatures. We’re funded by astrobiology programs from around the world. Our mission is to explore beyond the current understanding of what constitutes life—to expand its definition. It involves studying the far corners of our planet, to search for life in places it shouldn’t exist.”

  Phoebe glanced out the window. “Like where we’re headed.”

  “Certainly. The search below offers unique ways of looking up—beyond our world. It offers new approaches to search the stars for novel biosignatures of extraterrestrial life. So far, we’ve limited ourselves to looking for water on foreign planets or for the presence of methane or other organic compounds. LAB hopes to expand the scope of such searches.”

  “That’s why you’re studying these extreme depths?” Monk asked.

  He nodded. “Our team has been trying to break through the walls of accepted dogma. For example, it has been believed for decades that the emergence of life happened on Earth’s surface, where water and atmosphere are exposed to sunlight and UV radiation. My goal is to prove otherwise. To show that life could have started in the subsurface environment, fueled by chemical energy. It’s what sparked my interest in Earth’s piezosphere—a layer that covers the deep sea and five thousand meters below the sea floor. In deep marine sediments, miles underground, we’ve found life where it shouldn’t be. Life that is so metabolically slow that one cell division takes a thousand years.”

  Phoebe frowned. “And your study of such strange life hopes to expand the search for extraterrestrial biosignatures?”

  “I believe it can. I’m convinced we have a greater chance of discovering life on another planet by searching for slow life, buried deep. Fast life on the surface comes and goes quickly. While planetary surfaces receive plenty of energy from their suns, they’re also susceptible to annihilation by meteoric impacts or stellar flares. Whereas subsurface life is protected and preserved from such disruptions, and thus more stable.”

  Phoebe blinked as she absorbed this information.

  Datuk stared past her shoulders and nodded toward the window. “Looks like we’re back in open water.”

  Phoebe swung around.

  The murkiness had indeed cleared.

  Datuk reported from his bank of sensors. “Salinity has dropped back to normal.” A quizzical note entered his voice. “And it keeps dropping. And oxygen levels are also rising.”

  Phoebe stared out at the dark ocean. By now, they had dropped below seven thousand meters, well into the hadal zone. “That’s expected at these depths,” she said. “The water in these deep ocean trenches is richer in oxygen due to the lowered salinity and higher pressure.”

  “But look at these numbers,” Datuk said.

  Phoebe drew her gaze from the seas to his small glowing screen. The DO reading—dissolved oxygen—steadily climbed. It crossed 12 mg/L as she watched—20% higher than expected. Similarly, the salinity had dropped below 29‰. Seawater typically stayed above 33‰, even at these extreme depths.

  She shook her head. “Something must be wrong with the external sensors. Those numbers can’t be right.”

  Bryan spoke from the pilot’s seat, interrupting them. “What’s that rising under us?”

  Phoebe turned around. The others bent to their respective windows. She stared between her knees. The lower curve of the dome allowed her to look straight down.

  Gasps rose around her.

  She simply choked, strangled by astonishment.

  Below—and rising swiftly toward them—the world shimmered and glowed. Traceries of emerald and cerulean fire lanced across the view, shooting off in hundreds of directions. Other areas pulsed through a radiant kaleidoscope.

  She knew what she was witnessing.

  Bioluminescence.

  They continued to drop toward the shining, unearthly landscape. As they did, the expanse stretched in all directions, fading into darkness at the edges. She pictured walls towering to either side, the cliffs of the Tonga Trench. They had dropped down its center, not wanting to risk brushing against its rocky sides.

  “Is that what I think it is?” Adam asked behind her.

  Phoebe remembered the spread of black oil noted on the bathymetric map of the trench. It had marked the presence of a vast coral forest, a thousand feet tall and covering two hundred square miles.

  Only this forest wasn’t black.

  As the Cormorant dropped toward the bottom, the bioluminescent jungle grew into focus. It was a fiery wonderland of dark branches that blinked, shimmered, and glowed in radiant hues. Trunks of coral, as thick around as redwoods, climbed from below. Their roots were so deep that not even the forest’s brilliance could illuminate them. Directly under the Cormorant, the weave of branches formed a continuous canopy that rose and fell across the field of view.

  “Dumping ballast,” Bryan said. “Going for neutral buoyancy.”

  He hit switches, ejecting five-kilogram weights, one after the other.

  As their descent slowed, Phoebe could not shift her gaze away. The Cormorant lowered until it hovered above the shimmering canopy. Past the glow, she discerned the fringes of polyps that crowded the nearest black branches.

  The polyps were all a uniform emerald, sprouting from the hard black skeleton of the coral.

  She flashed to the day before, picturing the lone sentinel of coral that she had sampled outside Titan Station Down. Was this the same species? They were still too high to say for sure. Yesterday, she had judged the tree by the station to be an ancient giant. If the forest below was the same species, then that tall specimen was a mere seedling.

  She wished Jazz were here, to witness this firsthand, too.

  Datuk murmured behind her, “Akah Bahar.”

  “What was that?” Adam asked him.

  “It’s the Malay name for black coral—which seemed appropriate.”

  Phoebe kept her gaze outside. “Why? What does it mean?”

  “It means Root of the Sea.”

  Phoebe stared at the vast expanse and corrected him. “This looks more like the Root of the Entire World.”

  15

  January 23, 9:55 P.M. NCT

  Two miles under the Coral Sea

  Jasleen Patel rubbed her eyes as she leaned back from the optical microscope. She had spent two hours reviewing slides from the seventeen specimens she had collected with Phoebe. A headache knotted behind her eyes. She blamed it on a dip in blood glucose from skipping dinner. But she had not wanted to disappoint her boss.

  She stretched a kink from her neck and checked the time on the open laptop next to her. Phoebe should be at the bottom of the trench by now. A flicker of envy traced through her. She threw cold water on it.

  I’ll get my own chance soon.

  She reached over to the laptop and reviewed her work. She had spent the day cataloguing the specimens’ morphological and physiological details. It required delicately extracting centimeter-size cores from the chunks of coral secured inside the station’s high-pressure benthic chambers. Before they could be studied, each tiny sample had to be slowly equilibrated to the station’s one atmosphere of pressure.

  The work had been painstaking.

  Over the course of the day, she had studied each specimen, counting the number of polyp tentacles, noting their coloration, measuring their lengths and dimensions. She had run samples through a NovaSeq 6000 DNA sequencer. She had even used the lab’s dissecting microscope to tease out nematocytes—the venomous cells—from the tentacles. The latter were all unique, like fingerprints, and could help substantiate taxonomy.

  A chime sounded from her laptop, and an email alert popped up.

  Finally . . .

  She shifted over and opened the attached file. It had been sent from the team running the station’s scanning electron microscope. She had sent over samples of each coral to have their sclerites—their calcareous endoskeletons—recorded from multiple angles. It was yet another means of classifying each species. No two corals were alike in their carbonate structure.

  She sifted quickly through the scanning photos, but in particular she searched for Specimen A17, named after the quadrant from where it had been collected. She pictured the towering black giant, festooned with emerald polyps, a lone Christmas tree slowly growing in darkness.

  She brought up the scan of its sclerite. It showed the specimen from multiple angles. The micro team had done a wonderful job.

  She brought her nose closer to the screen, shifting her glasses higher. “What are you?” she whispered to the mystery before her.

  Specimen A17 continued to confound, baffle, and intrigue her. It had all the characteristics of a black coral, but its polyps had eight arms instead of the expected six. Plus, its sweeper tentacle had been monstrously long, tipped by a stinging nematocyst that was four times the size of any others. Even this scan of its sclerite showed a density of polyp cupping that she had never witnessed before in another coral.

  No wonder you little green guys evolved an escape method. You’re all too crowded in there.

  She pictured the little polyps jettisoning in alarm when Phoebe had collected a sample, even attacking the extraction claw.

  Still, the most frustrating part of the day had been her attempt at analyzing this specimen’s DNA. She kept getting an error code on the sequencer. Knowing she had the other specimens to record, she had finally given up. She had planned on waiting until Phoebe returned to try again.

  She checked the time.

  Maybe I should give it another go myself.

  Jazz hated to fail her friend. She had wanted to complete her study today and send her results to Phoebe on the Titan X, to have them waiting for her when she finished her dive.

  Decided on the matter, Jazz rolled her chair away from her station. At this late hour, others were still working across the biology lab, all bent in various postures of concentration. She stood up with a jaw-cracking yawn and headed out of the lab. She crossed the central hub and descended to the next tier. The department’s wet lab and high-pressure benthic chambers were on this lower level. It was also where the curve of ROV stations were located.

  Even at this hour, every ROV cubicle was occupied.

  She turned her back and pushed into the high-pressure room. It was like walking into an aquarium. The tanks were stacked four high and ten across, all fronted by the same glass that ringed each tier. Under each chamber, a set of caliper controls stuck out, not unlike those that operated a claw machine at an amusement park. It allowed a researcher to manipulate a set of drills, corers, and suction tubes inside the pressurized tank.

  Before rerunning the DNA sequencing on Specimen A17, Jazz wanted a fresh sample. Two other biologists were already at work in here. Luckily, no one blocked her tank, which would have required her to wait her turn.

  She stepped to the benthic chamber. Their names—Reed/Patel—had been scrawled in an upper corner of the tank’s glass, written in erasable black marker. It was how each researcher staked a claim to a tank. It was crude but effective.

  Only now a new name had been written under theirs: 김종석. Though she was not that familiar with the various Asian alphabets, she was fairly certain it was Korean hangul. The researcher had to be Dr. Kim Jong Suk, who studied crustaceans, specifically shrimp species. The man was equally known for his foul temper and rude manner, especially toward the female researchers.

  Inside the tank, Jazz had meticulously sectioned off each of her coral samples into separate plastic trays and positioned across the tank’s bottom. Dr. Kim had simply dumped in two dozen large shrimp with translucent pink shells. Jazz recognized them as a species of Lucensosergia lucensi, or Sakura shrimp, named after the Japanese cherry blossom. They swam, kicked, and crawled throughout the tank. Their excrement dotted the bottom as if an overzealous waiter with a pepper grinder had seasoned the chamber.

  She huffed out her exasperation. The scientists had been warned that these high-pressure chambers would have to be shared among them, but currently there were four others that remained empty. It required hours to prep one, and clearly Kim hadn’t wanted to bother with those extra steps and simply threw his samples into their tank.

  “What a jackass,” she whispered as she grabbed the manipulator controls.

  Phoebe would be equally pissed.

  Jazz stared across the trays, which had been shifted into disarray by the antics of the busy shrimp. One of her specimens—G5—had been tossed out of its place. She used a claw to return the chunk to its proper tray. She then shifted over to A17, ready to get to work, bringing up a pincer and drill.