A blue abyss of ignorance: we know Mars better than the bottom of the sea

There are photographs in every home. Of children, granddaughters, parents, grandmothers. People are usually shown in a slightly artificial position, in the middle of some activity that defines them or at an emblematic moment in their lives: about to kick a ball, on top of a mountain, or dressed in a wedding suit. In the dining room of our house, there was a photograph of my great-grandfather Manelet next to a three-meter hammerhead shark. It had accidentally become entangled in the net of the boat in which he was fishing, and when they arrived at the port of Arenys, someone immortalized that extraordinary catch, which even made the news in the United States. The Vanguard. Like everything that becomes normalized because it forms part of the foundation upon which one acquires the use of reason, perhaps I never attributed to it the importance it had. It was simply there. It was part of the domestic landscape, like the rosebushes and loquats in the yard, the pottery workshop on the porch, or the Creedence Clearwater Revival vinyl records.

Without establishing any conscious connection, years later I began collecting videotapes with documentaries about sharks. And when people asked me what I wanted to be when I grew up, I replied that I wanted to be one of those individuals who went into the sea inside a cage surrounded by sharks. The first time I saw one of these animals, however, it wasn't inside a cage but in open water, ten meters below the surface. It was a whitetip reef shark that couldn't have been more than a meter and a half long. I saw it appear out of nowhere and slowly approach. Despite my obsession with sharks, I never imagined what it would be like to come face to face with them.

From the first blow, I was captivated by the shark's swimming style and by a body language that, in a non-verbal but powerful way, proclaimed that this form had evolved over four hundred million years to remain inextricably linked to that piece of contemporary salt water. As the shark approached, I remained motionless, suspended in the water column. When it came within a few meters, it accelerated and suddenly turned, disappearing once again into the immensity of the sea. I wasn't the least bit afraid, not because I'm particularly brave or reckless, but because in the sea, the strength of the centuries-old bond between life forms and the liquid medium predominates over any other perception.

A few years later, the sun rose, and from the bow of a boat in the Indian Ocean, Hassan scrutinized the surface of the water, so still it seemed like mercury. We sailed slowly, and without taking our eyes off the water, the Maldivian with waist-length curly black hair signaled with his hands to the skipper to change course every few meters. Half an hour later, he ordered the engine to stop and urged us to gear up and jump into the water immediately. Once inside, at a depth of twenty meters and with no other reference point than the occasional glimmer of a stray scale, he did the same: moving forward, turning slightly, stopping, inspecting the blue, turning a little more and continuing on, ascending or descending a few meters, stopping again, now to the left, now. And so, half an hour later, he pointed in a direction. A few moments later, a shadow appeared that materialized into a magnificent hammerhead shark. It measured more than three meters and swam slowly with no fixed course.

Just as the small whitetip shark had done, the hammerhead shark proclaimed that same relationship of interdependence and even identity—"I am the sea," it called out at the top of its gills—with the liquid immensity surrounding it. However, thanks to the unique shape of its head, which allowed it excellent stereoscopic vision forward and backward, as well as highly accurate depth perception, it asserted it in a more specific and, therefore, more majestic way.

Not knowing

Although it was an unforgettable experience, it wasn't until I started typing these lines at the suggestion of this journal that I was able to rationalize it—writing already has that. Now I realize there's a certain closure between the photograph of my great-grandfather and the encounter with the hammerhead shark. The most obvious common element is the shark, but it's not the only one. Nor the most important. After thinking a bit, I see very clearly that the overwhelming evidence that links those two snapshots is ignorance.

More specifically, the unfathomable ignorance aroused by the immensity of the sea. An ignorance that transforms the appearance of a hammerhead shark in the middle of an infinite blue into an almost mystical surprise. It is a true apparition of a power greater than human. Because water, which seems as void as space, is only capable of offering this imposing result: a shark, based on time and very primordial elements—matter, laws of physics, evolution. It's as if the entire ocean were telling us, "This is what I can do." Before, there was just water and a few molecules. Now there's this: a shark. A lump of matter that condenses the information accumulated over more than three billion years of failed combinations and evolutionary dead ends into an adapted but imperfect hydrodynamic form—evolution doesn't generate perfection, it does what it can—and which, precisely for that reason, is mysterious, elegant, and stupendous.

Ignorance about the oceans is difficult to tame. Scientific research has done so, in part, but so has the experience of the people who go out to sea day after day to earn a living. I like to think that the Hassan's curves, both those he arranged on the boat and those he made underwater, obeyed a criterion that perhaps cannot be explained in a graph or an equation, because it is constructed with data that, collected by the senses and involuntarily compiled throughout the body over thousands and thousands of more intuitive than rational responses to new stimuli, and that, in a seemingly inexplicable way, generate the conditions for the surprise of finding a hammerhead shark in the abyss.

If the surprise of a shark is enormous, however, it is because the ignorance that the sea inspires is comparable only to that provoked by outer space. Now, the proximity of the sea and facts such as, from a beach, with water up to your waist, at a distance of just a foot, the ground sinks to a depth of 600 meters, make it a different kind of ignorance. It's acceptable not to know much about an exoplanet located four light-years away. Not knowing anything about the sea in front of you, where you've swum since you were a child, has a certain absurdity. It's hard to accept that the surface of Mars is known in greater detail than the seabed, or that more people have been to the Moon than to the deepest part of the sea.

This widespread ignorance makes the sea a source of mystery and inexhaustible fascination. But how widespread is this ignorance? According to a study recently published in the journal Science Advances Regarding the seabed, 66% of the planet's surface is covered by waters with depths greater than two hundred meters. Of this entire surface, 3,823 square kilometers have been directly observed—with images—less than 0.001% of the total. This is equivalent to approximately half the province of Barcelona.

The problem with this data is not only that it is limited, but that it is biased: most of the images were taken in just three countries: Japan, New Zealand, and the United States. Therefore, the idea we have formed of the seabed is certainly incomplete, and, in all likelihood, substantially different from reality. To understand the extent of this bias, it is enough to consider that the surface of solid land on the planet is 148.94 million square kilometers. Would it be possible to describe the Earth if we had only seen an area of 1,489 square kilometers—approximately the territory of Alt Urgell—most of it in just three countries?

It doesn't take much common sense to assume that understanding the entirety of a complex system from such limited data is problematic. But even more problematic is that obtaining more data is extremely slow and complex. Delving into the depths is technically challenging. In the 2010s, there were 79 platforms (underwater vehicles) capable of exploring the seafloor, but each one could cover only a few square kilometers per year. If the number of platforms reached 1,000, and each one could X-ray three square kilometers per year, it would take more than 100,000 years to obtain a complete picture of the seafloor.

The cold search

Beyond technical difficulties, there are other factors that have historically conditioned oceanographic research and, therefore, have promoted certain types of knowledge to the detriment of others. In the book Science on MissionIn "The History of Science at Harvard University," Naomi Oreskes, a professor of the history of science, analyzes how the United States Navy's interest in oceanography since World War II influenced what we know and don't know about the oceans today.

The United States was the leading scientific power of the 20th century. More than 70% of all Nobel Prizes were awarded to American citizens. Therefore, the type of research conducted in this country has had a direct influence on global knowledge. With the tensions of the Cold War and the rise of submarines as weapons of war, the United States began investing money in a quest to optimize underwater navigation, the detection of enemy vessels, and the use of self-propelled underwater weapons. The ocean, then, was nothing more than a stage in which war took place, a space for transportation, communication, detection, and the possible firing of torpedoes or nuclear missiles. This vision led to research primarily on the shape of the seafloor, currents, and variations in salinity and temperature. In other words, a type of oceanography that prioritized physics was promoted. The study of life and the conditions that made it possible took a backseat.

The fact that the sea was considered a mere physical space and not a reservoir of life facilitated the uncontrolled proliferation of trawling, whaling, and the dumping of chemical, plastic, or nuclear waste. This last case is an example that perfectly illustrates the idea we have had of the sea for most of the 20th century. During the International Geophysical Year, held from 1957 to 1958, the main objective set by the oceanographic community was the use of the seabed as a repository for nuclear waste.

Furthermore, this was not done in secrecy, but with the pride of providing a definitive solution to a problem of importance to humanity. In fact, the United States had already been dumping nuclear waste into the sea for ten years. Ships transported it to the Fallaron Islands, fifty kilometers off the California coast, and simply dumped it overboard. If they floated, they were sewn up with bullets to let in water, make them weigh more, and eventually sink. But, of course, plutonium, uranium, and other radioactive materials came out through the bullet holes. It wasn't until the 1990s that this practice was stopped, after more than 200,000 tons of radioactive waste had already been dumped at various sites. And not just in the United States. The Soviet Union, Japan, New Zealand, South Korea, and many European countries also did so.

This dominance of physical research over biological research has not only led to further degradation of marine ecosystems but has also created disconcerting gaps in knowledge. In 2004, Japanese scientists captured for the first time images of a giant squid, one of the deep-sea creatures that has fueled the most myths and legends. The images could have been captured much earlier because, already in 1965, the researcher Frederick Aldrich had proposed to study this leviathan with the submersible Alvin, which was, in fact, operated by the US Navy.

If scientific priorities had been different, we might have known sooner that the eyes of these beasts, with a diameter of up to 27 cm, are the largest in the animal kingdom and have the sensitivity to detect the very weak fluorescence emitted by the low density of plankton found in the depths of the water at full speed in a hunting maneuver never seen before but that must be one of the most violent of all those that occur on the planet.

In fact, these eyes are the result of a process of coevolution between prey and predator that, like a true arms race, promotes characteristics that maximize the success of both. When the predator triumphs and devours the world's largest invertebrate—it would be hard to house it on a bus—the cetacean's digestive system coats the cephalopod's indigestible beak with a substance that, when excreted, is known as ambergris, and which, historically, has been used only as a souvenir by royalty.

Although, deep down, ignorance about the giant squid, one of the most fascinating creatures on the planet, highlights what happens with many other species such as the blue whale, the sperm whale itself, or fish that are of interest as a food source. Very sophisticated population models are currently available, but as Oreskes points out, no matter how refined the models are, if we don't introduce the correct data, we won't be able to know how a population is evolving and, therefore, we won't know if we are overexploiting it until it's too late. And for many commercial species, information is lacking: the number of individuals in the population, their lifespan, or the percentage of offspring that survive the early stages of life is unknown.

Dioxide of ignorance

Another major gap in our knowledge of the ocean relates to climate change. Although oceanographers were among the first scientists to show interest in the phenomenon, they struggled to secure funding for in-depth research. In 1953, American physicist Gilbert Plass warned that the burning of fossil fuels was increasing atmospheric carbon dioxide levels and that this would lead to a global warming of one and a half degrees per century.

Oceanographers immediately reasoned that if there was more carbon dioxide in the atmosphere, the oceans would absorb some of it. Could this absorption mitigate the warming of the air? What effects would excess carbon dioxide have on marine waters? These questions were posed as early as 1958, but serious research projects on the issue didn't begin to be mounted until the late 1980s. What would we know now about the role of the oceans in climate change if we had started studying them differently?

Today we know that carbon dioxide makes the water more acidic and that, under these conditions, the calcium carbonate shells of many organisms don't develop properly because this material dissolves more easily in acidic environments. This affects shells and snails as well as many of the tiny creatures that make up plankton and represent the base of the marine food web. This isn't good news considering that more than two billion people depend on the sea as a direct source of food.

Despite being the cradle of life, it's clear that the sea is not our element. This, coupled with its immensity, means it will probably remain a place more unknown than known. If politicians allow it, science will continue to advance, and we will learn more and more about the oceans. However, the way science advances is curious: as questions are answered, new ones emerge in a branching process that sometimes seems endless, imbuing the process with an inexhaustible fascination. Be that as it may, there will always be a residue of ignorance about the sea. And this residue, combined with the new questions brought about by science, will continue to fuel surprises like the furtive discovery of a hammerhead shark in the middle of the vast blue abyss.