A deep-sea chimaera (ghost shark) with pale skin and large eyes, captured by an ROV’s red-light camera in the dark Pacific abyss.
Imagine descending into a world of perpetual darkness, where the pressure would crush a submarine like a tin can, and the only light comes from the bioluminescent glow of creatures that have never seen the sun. This is the deep Pacific Ocean, and for the first time, remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) are giving us a front-row seat to some of its most bizarre inhabitants—sharks that look like they belong in a science fiction movie.
These ‘alien’ sharks, with their pale, ghostly skin and oversized, glowing eyes, are not visitors from another planet. They are the chimaeras, also known as ghost sharks, and the sleeper sharks, ancient fish that have thrived in the abyss for hundreds of millions of years. But why do they look so strange to us? And what are they doing at depths of 1,000 to 4,000 meters, where sunlight never reaches?
The answer lies in a combination of evolutionary adaptation and the incredible technology that allows us to observe them without disturbing their fragile world. As we dive deeper into the Pacific, we’re not just discovering new species—we’re rewriting what we know about life on Earth.
The Unseen World Below
The deep ocean is the largest habitat on our planet, covering more than 60% of Earth’s surface, yet we have mapped less than 20% of its seafloor in detail. For most of human history, the abyss was a place of myth and mystery, too deep and too dark for us to explore. But in recent decades, a new generation of robotic explorers has changed everything.
ROVs like NOAA’s Deep Discoverer are essentially underwater drones, tethered to a ship on the surface. They are equipped with high-definition cameras, powerful lights (often red, which is invisible to many deep-sea animals), and robotic arms for collecting samples. AUVs, on the other hand, are autonomous—they swim pre-programmed routes, recording video and data without a human pilot in real time. Together, these machines have opened a window into a world that was once completely inaccessible.
During recent expeditions in the Pacific, including around the Hawaiian archipelago and the Pacific Remote Islands Marine National Monument, these vehicles have captured footage of sharks that look like they were designed by a Hollywood special effects team. The footage is not just a visual spectacle—it’s a treasure trove of scientific data.
Meet the ‘Ghost Sharks’
When we say ‘ghost shark,’ we’re not talking about a spooky spirit. Chimaeras, to give them their proper name, are cartilaginous fish that split from true sharks and rays about 400 million years ago. They are ancient, slow-growing, and perfectly adapted to life in the deep.
Their most striking feature is their skin—it’s often pale, almost translucent, with a smooth, scaleless texture. This coloration is a form of camouflage in the dark, where there is no sunlight to reflect. Their eyes are large and highly sensitive, allowing them to detect the faintest bioluminescent glow from prey or predators. And they have a unique feature: a venomous spine on their dorsal fin, used for defense.
The ‘alien’ look comes from their unusual body shape. Chimaeras have a blunt head, a long, tapering tail, and large, wing-like pectoral fins that they use to ‘fly’ through the water. When you see one gliding out of the darkness, it’s easy to understand why early explorers might have thought they were seeing something otherworldly.
But chimaeras are not just curiosities—they are important members of the deep-sea ecosystem. They feed on crustaceans, mollusks, and small fish, and they are prey for larger predators like sleeper sharks. Their slow growth and low reproductive rates make them particularly vulnerable to human activities like deep-sea trawling, which often catches them as bycatch.
The Giants of the Abyss: Sleeper Sharks
If chimaeras are the ghosts, sleeper sharks are the monsters of the deep. The Pacific sleeper shark (Somniosus pacificus) can grow to over 7 meters (23 feet) long, making it one of the largest predators in the ocean. Despite their size, they are slow-moving and sluggish, with a metabolism that matches the cold, dark environment they call home.
Sleeper sharks are scavengers and opportunistic predators. They have been observed feeding on everything from fish and squid to the carcasses of marine mammals that sink to the seafloor. Their jaws are powerful, and their teeth are designed for gripping and tearing, not for slicing like those of surface-dwelling sharks.
The footage from ROVs has revealed surprising behaviors. For example, sleeper sharks have been seen using their snouts to root around in the sediment, possibly searching for buried prey. They also appear to be attracted to baited camera landers, which suggests they have a keen sense of smell and are always on the lookout for an easy meal.
The Technology That Makes It Possible
Spotting these sharks is no easy feat. The deep sea is a hostile environment: pressures can exceed 400 atmospheres, temperatures hover just above freezing, and there is zero natural light. ROVs and AUVs are engineered to withstand these conditions, with pressure-resistant housings, specialized cameras, and lighting systems that don’t disturb the animals.
One of the key innovations is the use of red light. Many deep-sea creatures are sensitive to blue and green light, which are the colors that penetrate deepest in the ocean, but they are often blind to red. By illuminating the scene with red light, scientists can observe natural behaviors without scaring the sharks away or blinding them.
Another important tool is the baited camera lander—a frame with a camera and a bait canister that is dropped to the seafloor and left to record for hours. This passive approach allows scientists to capture footage of animals that might be frightened by the noise and lights of an ROV.
The result is a more complete picture of deep-sea life. We’re not just seeing a shark swim by; we’re seeing how it moves, how it interacts with its environment, and how it responds to the presence of food or potential threats.
Why Do They Look So ‘Alien’?
The ‘alien’ descriptor is a product of our own perspective. We are used to seeing sharks that are sleek, streamlined, and often dark-colored, like great whites or hammerheads. Deep-sea sharks have evolved in a world without sunlight, where the rules are different. Their pale skin is not a sign of sickness—it’s a form of camouflage that makes them nearly invisible in the dim blue light of the deep.
Their large eyes are a direct adaptation to low light. In the abyss, the only light comes from bioluminescence—the flashes and glows produced by other creatures. A shark with bigger eyes can capture more of that faint light, giving it a better chance of spotting prey or avoiding predators.
Even their body shapes are a response to their environment. The deep sea is a vast, open space with few obstacles, so there is no need for the streamlined, fast-swimming bodies of surface sharks. Instead, chimaeras have evolved a more efficient, slow-cruising design that conserves energy in a world where food is scarce.
The Scientific Significance
These sightings are more than just cool videos. They provide critical data that helps scientists understand the biodiversity of the deep sea and the roles these sharks play in the ecosystem. For example, by documenting the depth ranges of different species, researchers can create more accurate models of where they live and how they might be affected by human activities.
The footage also reveals behaviors that have never been observed before. For instance, some chimaeras have been seen flashing their bioluminescent spots, which may be a form of communication or a way to attract mates. Sleeper sharks have been observed scavenging on whale carcasses, which are important ‘food falls’ that sustain a whole community of deep-sea organisms.
This information is crucial for conservation. Deep-sea sharks are increasingly threatened by fishing, especially as bycatch in trawl nets, and by proposed deep-sea mining operations that could destroy their habitats. By understanding where they live and how they behave, we can make better decisions about how to protect them.
The ‘Alien’ Narrative: Helpful or Harmful?
The media’s use of the word ‘alien’ to describe these sharks is a double-edged sword. On one hand, it captures the public’s imagination and draws attention to the wonders of the deep sea. It can inspire a sense of awe and curiosity, which is essential for building support for ocean conservation.
On the other hand, it can be misleading. These are not extraterrestrial creatures or newly evolved monsters. They are ancient, well-adapted species that have been around for hundreds of millions of years. Calling them ‘alien’ can make them seem less real or less connected to us, which might undermine efforts to protect them.
Scientists prefer to focus on the facts: these sharks are a natural part of our planet’s biodiversity, and they are in trouble. The ‘alien’ label might make for a catchy headline, but the real story is about the incredible adaptability of life and the urgent need to preserve it.
What’s Next?
As technology continues to improve, we can expect even more remarkable discoveries. New ROVs and AUVs are being developed with better cameras, longer battery life, and more sophisticated sensors. Some are even being equipped with artificial intelligence that can identify animals in real time, allowing scientists to focus on the most interesting observations.
There are also plans to expand deep-sea exploration to other regions, such as the Mariana Trench and the abyssal plains of the Pacific. Each expedition has the potential to reveal new species, new behaviors, and new insights into the history of life on Earth.
But exploration is not just about discovery—it’s also about protection. As we learn more about the deep sea, we must also work to ensure that it is not destroyed by human activities. The ‘alien’ sharks of the Pacific are a reminder that there is still so much we don’t know about our own planet, and that we have a responsibility to protect it.
The deep-sea sharks of the Pacific are not aliens—they are our fellow inhabitants of Earth, perfectly adapted to a world we are only beginning to understand. Thanks to the ingenuity of ROVs and AUVs, we can now glimpse their hidden lives and appreciate the beauty and complexity of the deep ocean. As we continue to explore, we must remember that these creatures are not just curiosities; they are vital parts of a fragile ecosystem that deserves our protection.
Summary
- ROVs and AUVs have captured rare footage of ‘alien’ sharks, including chimaeras (ghost sharks) and sleeper sharks, in the deep Pacific Ocean.
- These sharks are not new species; they are ancient, well-adapted creatures with pale skin, large eyes, and unique body shapes suited to the dark, high-pressure environment.
- The technology used, such as red-light cameras and baited landers, allows scientists to observe natural behaviors without disturbing the animals.
- The sightings provide valuable data on biodiversity, behavior, and habitat ranges, which are crucial for conservation efforts.
- The ‘alien’ label is a metaphor that can raise awareness but may also mislead the public into thinking these are extraterrestrial or newly evolved creatures.
FAQ
Q: Are ‘ghost sharks’ actually sharks?
A: No, chimaeras (ghost sharks) are cartilaginous fish related to sharks but belong to a separate subclass called Holocephali. They diverged from true sharks about 400 million years ago.
Q: Why do deep-sea sharks look so strange?
A: Their appearance is a result of adaptations to the deep-sea environment: pale skin for camouflage, large eyes to capture faint bioluminescent light, and slow, energy-efficient body shapes for a world with scarce food.
Q: How do ROVs and AUVs help scientists study these sharks?
A: These vehicles are equipped with high-definition cameras and lights (often red) that allow non-invasive observation. They can reach depths of thousands of meters and record behaviors that would be impossible to see otherwise.
Q: Are these sharks endangered?
A: Many deep-sea sharks are vulnerable due to slow growth, low reproduction rates, and threats from fishing bycatch and proposed deep-sea mining. The new data from ROVs helps inform conservation policies.
Q: Could the ‘alien’ look mean they are extraterrestrial?
A: No, the ‘alien’ descriptor is purely metaphorical. These are Earth creatures that have evolved over millions of years to survive in one of the most extreme environments on our planet.