By our third day at sea, we’d found it: a dozen bare and jagged piles of rocks surrounded by ocean the color of Windex. It was smaller than I had imagined, all told about twice the size of a soccer field. There was no white sand, no volcanic peaks, no palm trees, none of the trappings of other tropical island chains at this latitude, just razor-sharp umber peaks iced in a thousand years of bird shit—the whole of it resembling a kind of sinister Gilligan’s Island.

But we didn’t motor from the coast of Brazil more than a thousand kilometers across the Atlantic on a beach holiday or three-hour tour. We came to explore the waters deep below the sunlit surface. We came to collect clues from this place, known as Saint Peter and Saint Paul Archipelago, about how life on Earth first began—and how alien life might evolve on other planets in the solar system.

These are big, serious questions, and we’ve brought a big, serious team to investigate them, including a crew of more than 40 geologists, microbiologists, geophysicists, biologists, engineers, deep-ocean divers, and deck hands from a dozen nations. The team will spend the next two weeks aboard the M/V Alucia—a 56-meter (184-foot) research vessel operated through the Dalio Ocean Initiative—scanning the ocean floor, sampling rocks, analyzing water samples, and diving research submarines a thousand meters beneath the surface.

Nobody has ever explored these deep waters, and no one on the team knows what we’ll find.

“It’s a unique area, and so it might host some unique life systems,” says Frieder Klein, a marine geologist, who’s leading the scientific team from Woods Hole Oceanographic Institution (WHOI). Klein is standing barefoot on Alucia’s top deck in cargo shorts and a faded MC5 t-shirt, squinting in the noonday sun. A few hundred meters to the north, waves crash and fizz on the shores of the 15 bite-sized rock islets.

Klein tells me that below us, millions of years ago, the tectonic plates of the Mid-Atlantic Ridge began separating, causing a split in Earth’s crust. This rift has widened by about a finger’s width every year since, which is why Europe and North America are now separated by nearly 7,000 kilometers (4,350 miles) of ocean. Over the course of this very slow process, mantle rock, which usually lies hidden 6 kilometers (3.7 miles) below the crust, has been forced to the surface.

Mantle rock isn’t particularly rare; it covers wide swaths of the deep seafloor around the globe. Here, though, it’s much shallower, much more accessible—and it’s continuing to evolve as it interacts with seawater. “There is really no place like this in the world,” Klein says, wiping his forehead of sweat.

Most researchers never bothered. Seeking out extreme life requires traveling to some of Earth’s most far-flung and extreme environments. Only a handful of microbiologist and geologists have had the will, fortitude, and resources to endure weeks in the triple-digit heat within African mines, or months in the frozen expanses of Antarctica, or years sifting through the polluted oil fields of Dagestan to find answers.

Which makes it all so much more guilt-inducing for our team to be lounging aboard the Alucia. While the dangers and discomforts of bobbing around in the middle of the Atlantic 700 miles from the closest hospital are real and many, we’re at least comforted by the borderline luxury of our living and work quarters, where every square inch of interior space acclimatized to a refreshing and humidity-free 72 degrees—so brisk that some of us futz around wearing sweaters and socks while the outside temperature climbs toward 100.

Tonight’s dinner, served in the mess hall, includes quinoa, steak, chicken, sautéed green beans, roasted potatoes, farmer’s salad, and homemade crème brûlée for dessert.

I grab a plate and scoot next to the two other lead researchers on the scientific team. Diva Amon is a deep-sea biologist from the Natural History Museum of London. She grew up swimming off the shores of Trinidad and Tobago and at an early age was fascinated with the diversity of sea life, especially the animals that dwelled beneath the curtain of permanently black waters. She’s come on the expedition in the hopes of finding large-scale chemosynthetic life, such as crabs, tubeworms, shrimp, or whatever else may lie beneath.

The following day, Schubotz, Amon, and Klein are standing in Alucia’s mission control, a dimly lit room plastered in wall-to-wall flashing monitors. Everyone is staring wide-eyed at a gargantuan video display of what looks like a rainbow pie with a few pieces missing.

With every passing second, a few more pixelated lines appear on the image and the pie is a little more complete. Klein is entranced, subconsciously ooohing and aaaahing like a stockbroker excitedly watching the ticker of an initial public offering.

What the scientists are looking at is a high-resolution bathymetric map (the underwater equivalent of a topographic map) of the seafloor below us—a rendering of data gathered by the Multibeam Echo Sounder System, a sophisticated sonar device, mounted to the bottom of the Alucia. For the next two days the ship will circle the archipelago, moving farther away with every round, like a needle on a vinyl record playing in reverse. As we pass over the ocean floor the Multibeam will scan every nook and cranny down to a resolution of about 3 meters and down to a depth of 1,200 meters.

“Nobody has ever seen any of this before,” says Klein. “It’s all very exciting.” He is looking for anachronisms on the otherwise rather featureless underwater cliff. If active hydrothermal vents are here, they’ll likely be marked by telltale spires of carbonate.

Carbonate is a common substance that can be forged from many different processes. Calcium carbonate, which makes up the shells of marine organisms, covers more than half of the ocean floor. The remains of these dead organisms makes up the white stuff in the toothpaste you brushed your teeth with this morning and are in the concrete of the sidewalk you walked on outside your front door.

But the carbonate Klein is looking for is likely not created by biological activities but from minerals coming out of solution when scalding hydrothermal fluids meet cold seawater.

“There’s something promising here,” says Klein. He points to a peculiar outcropping on the western slope of the island chain. He says it seems unlikely that a rock just tumbled down from above and landed in this spot. It looks as if the structure emerged from the rocks below. “At minimum,” says Klein, “this area is worth exploring.”

Alan Scott, the pilot for Nadir and Alucia’s submarine team leader, is beside Wollermann, packing handfuls of candy bars and potato chips into a backpack should we get hungry along the way. “It’s easy, mate,” he says in a thick Scottish brogue. ”It’ll go by so fast you won’t even know what happened.”

Strangely, one thing that hasn’t crossed my mind this morning are the dangers involved cruising around along an unexplored seafloor of the Atlantic in a pressurized bubble, 1,000 meters below the ocean surface and a thousand kilometers from the nearest hospital, or airport, or doctor. When I asked Klein if he ever worried about the dangers of this kind of research, he demurred. “The only thing dangerous about it is to have spent a year-and-half planning this trip and come home empty-handed,” he chuckled. “The rest of it, riding in subs, sailing out here? That’s the fun part.”

Amon was a tad less sanguine. Days earlier she had told me a story about the Johnson Sea Link, a four-person submarine. In the summer of 1973, the same year the sub was first launched, a team of two pilots, an ichthyologist, and dive master, headed out on what was considered a routine dive 24 kilometers (15 miles) off the coast of Key West, Florida. The mission was to recover a fish trap from a sunken destroyer 100 meters below the surface.

While attempting to ascend, the Sea Link got caught on a cable extending from the sunken ship. The passengers sat back, relaxed, and waited for help. With the emergency oxygen reserves onboard, the pilots estimated they had about 42 hours before they suffocated.

Hours passed. The temperature plummeted to 42 degrees. Soon the passengers were suffering from hyperthermia. Worse, their calculations for fresh air were far too optimistic. The carbon dioxide levels began to rise to dangerous levels.

Eight hours after the pilots called for help a Navy support ship arrived and made several attempt to disentangle the sub. Nothing worked. The passengers began to lose consciousness.

The Sea Link was finally freed 32 hours after it had been launched. Two members of the sub team were dead of carbon dioxide poisoning; the other two were treated immediately and would live.

While the Johnson Sea Link was an extremely rare disaster and happened over 40 years ago, it’s impossible to overlook the fact that diving hundreds of meters deep in a transparent acrylic sphere the size of a phone booth has implicit risks. Motors can fail, electronics can short, lost fishing nets can entangle. Fortunately, though, the new generation of submarines are built with so many levels of redundancy and fail-safes, the chances of anything bad happening are remote. Of the hundreds of dives Deep Rover and Nadir have made, the crew members here have never experienced a problem.

“There are risks with any research, for sure,” said Amon said. “But to me, the rewards so far outweigh any of that. It’s incredible to be out here doing this kind of field research.”

A half-hour later, I’m about to experience those rewards for myself. At 10:00 a.m., I’m standing in socks at the foot of a steel staircase. Below me is Nadir’s open top hatch. Scott is sitting inside the sub guiding me in. “Okay, now, go slow,” he says. With a few torso twists and some sloppy footwork, I manage to wriggle in to the passenger seat. Following me is Susan Humphris, a geologist who will be surveying the underwater terrain and biology during the dive.

Scott seals shut Nadir’s hatch, gives the deckhands a thumbs-up, and we slowly creep out along the ship’s aft deck toward open water. Another thumbs-up and a crane lifts us from the deck until we’re swinging a dozen feet in the air like the pendulum of an old clock. I peer between my feet and see the Alucia crowded with crew and researchers. Between them, Klein and Wollermann roll out behind us in Deep Rover. In front of us, there is nothing but horizonless blue ocean.

We lower down into the water, splash at the surface, detach from the guide rope, and float away from the ship. “Okay, all clear,” says Scott into the sonar radio. With a gurgle of bubbles we sink below until there’s nothing but gradients of blue water all around. It’s stunning.

That evening Schubotz is in a makeshift laboratory jostling between cases of sparkling water, condiments, and cases of Brazilian beer. She is organizing test tubes on a cutting board covered with what looks like black dust. Over the past few days, Schubotz has been soaking the samples in hydrogen, carbon dioxide, and methane, hoping to spark some kind of reaction. She’s also been trying to “feed” them heavy carbon. If there are microbes on the rocks, they’ll likely consume the heavy carbon and become measurably heavier.

Cells in the human body, such as those in the small intestine, can replicate, or “turn over,” in just a matter of days. The turnover of some deep microbes, however, can take weeks to months to years or even decades. “It’s a lot of detective work, which makes it so fascinating,” she says. “You’re dealing with just such a crazy dimension.”

Schubotz and the rest of the scientific team are certain that hydrothermal activity occurred here at Saint Peter and Saint Paul Archipelago, but suspect that the activity occurring now, if it’s occurring, is likely lower-temperature, subtler and slower than at most other vent systems.

Over the next several months, Schubotz will take the samples back to the laboratory in Bremen, Germany and try to determine if the heavy carbon has been consumed, which will prove that microorganisms are active—that the rocks here are harboring hydrothermal life. “Only time will tell,” she says, shooting a smile.

On our last day here, we finally have the opportunity to set foot on dry land. Not as if there’s much of it, and not as if there’s much to see. Nothing grows on these little islets; there is no sand, no shade. The only people who live here are a crew of shirtless Brazilian Navy sailors who rotate every fortnight. As we approach in a smaller tender boat, the sailors wave us in. We tie up, climb a ladder over a sheer wall of rocks, and gather on an elevated wooden boardwalk.

Charles Darwin came here in 1832 while on a 5-year cruise around the world aboard the HMS Beagle. Upon landing, he described being surrounded by two species of pelicans and gulls, so “gentle and stupid” they remained perfectly calm, and perfectly still in his presence, surely because they had never seen humans before.