MYSTERIES OF THE ABYSS
THE CREATURES UNKNOWN TO SCIENCE THE MISSIONS TO MAP THE ENTIRE OCEAN FLOOR THE PLANS TO BUILD A PERMANENT DEEP-SEA HABITAT THE CELL-LIKE STRUCTURES THAT MAY HAVE SEEDED LIFE ON EARTH
The deep sea is Earth’s last unexplored domain. For the longest time, this enigmatic ecosystem has held within it answers to some of the most important questions in science. Now, a new wave of technologies are powering discoveries that will help us put together the story of Earth’s final frontier
1 DID LIFE BEGIN IN THE DEEP SEA?
Life on Earth began about four billion years ago. Where and how those simple cells first sparked into life remain tantalising mysteries, but evidence is stacking up that they could have first emerged in the deep ocean.
In 2017, palaeontologists identified microscopic tubes and filaments made of iron-rich haematite lodged within rocks formed between 3.77 and 4.28 billion years ago. The rocks are a rare fragment of primeval oceanic crust preserved on land (most of the seafloor gets dragged back into the Earth’s mantle, melted and recycled into new crust). The tiny formations have the characteristic shape of microbes that live today on deep-sea hydrothermal vents – the hot springs that form underwater at the edges of tectonic plates.
The fossil find lends support to a theory put forward in the 1990s by NASA chemist, Dr Michael Russell. His idea is that the templates for living cells were provided by tiny rocky pores inside the chimneys of hydrothermal vents. A specific set of circumstances would have been essential for this to happen, in particular the temperature can’t have been too high or the first signs of life would have been immediately scorched. Also, the fluids pouring through these vents would have needed to be alkaline to set up the conditions that generate energy in all living cells today.
Most vents, known as black smokers, are blisteringly hot and strongly acidic. But one incredibly rare formation called The Lost City, located in the Atlantic Ocean, provides the right set of conditions. What’s more, white smokers like this one are thought to have been much more common on the younger Earth. More clues that this could have been where life got going are coming from laboratories a long way from the abyss. In California, at NASA’s Jet Propulsion Laboratory, space scientists Dr Laurie Barge and Erika Flores have been growing tiny hydrothermal vents and successfully generated amino acids, an important building block of life. Meanwhile, at University College London, Prof Nick Lane’s team built a reactor to simulate the conditions of an alkaline hydrothermal vent, similar to The Lost City. They combined a mixture of fatty acids and fatty alcohols that spontaneously formed a membrane enclosing a drop of liquid – a basic proto-cell.
The theory of life originating in hydrothermal vents raises a thrilling possibility that life could begin elsewhere in the Solar System in a similar way. Scientists suspect there are hydrothermal vents on Saturn’s moon Enceladus, and in the giant salty ocean that lies beneath an ice crust on Jupiter’s moon Europa. NASA’s Clipper mission may detect signs of a habitable ocean when it arrives in orbit around Jupiter and swings close to its icy moon in 2030.
2 HOW MANY UNDISCOVERED CREATURES LIVE IN THE DEEP?
One thing is clear: scientists aren’t going to run out of new, deep-sea species to find any time soon. In a recent three-year study in the Pacific Ocean, remotely operated vehicles (ROVs) photographed nearly 350,000 animals: fish, octopuses, corals, anemones, shrimp, squid, sponges, and sculpted, living mud balls called xenophyophores… the list goes on. Only one in five were known species. Not all the images were clear enough to identify, but most were organisms nobody had seen before.
Whenever scientists look in the deep ocean they’re pretty much guaranteed to find something new and unexpected. “It’s always an incredible adventure,” says Prof Randi Rotjan from Boston University, who just returned from co-leading a month-long expedition to the Phoenix archipelago in the central Pacific Ocean. Their mission on the Schmidt Ocean Institute’s RV Falkor involved studying the ecosystems on seamounts. With the ROV SuBastian, the team conducted 21 dives and clocked up 250 hours underwater, gathering samples and high definition video of corals, sponges and other intricate life forms.
Standard techniques for studying deep-sea species involve a combination of visual recognition and collecting specimens for detailed analysis. Environmental DNA (eDNA), which looks for DNA-containing cells and mucus shed by organisms in large samples of water, is becoming a quicker and cheaper way of finding out which species are in the vicinity.
Archives of genetic sequences from deep-sea species are gradually being built. One day it should be possible to know whether a giant squid or a Greenland shark or any other mysterious deep-sea denizen just swam by out of sight, from the DNA they left behind.
When Rotjan’s team have finished analysing their findings, they will undoubtedly be adding entries to the World Register of Deep-Sea Species, which in mid-2021 listed 26,599 species, a number that’s rising all the time. “It’s not just a catalogue of what’s there, but why they’re there, who they’re interacting with and what they’re doing,” says Rotjan.
An aspect of deep-sea ecology that Rotjan is studying is the immune systems of corals that can live for thousands of years. She wants to understand how they heal from attacks by coral-eating predators, or coral-livores. This could offer new insights into how innate immunity evolved among some of the earliest, multicellular animals on Earth. It could even have applications in medicine, because we share ancient ancestors with corals.
Expeditions such as Rotjan’s hold immense potential to inspire the public about the deep. Footage of deep-diving whale sharks and a pair of exquisite glass octopuses sparked enormous responses online. For Rotjan, these glimpses of deep-sea ecosystems are crucial reminders that we share the world with so much hidden life. “What we really need, as stewards of this planet, is to protect our neighbours,” she says.
3 WILL WE EVER BUILD A DEEPSEA BASE?
Technically speaking, there is nowhere in the abyss that’s entirely off limits to humans. A growing roll call of brave and curious people have paid brief visits to the ocean’s greatest depths. Earlier this year, Nicole Yamase became the first Pacific Islander, the third woman and the youngest person to descend into the Challenger Deep in the Mariana Trench, the ocean’s deepest point at close to 11 kilometres down.
But going down and staying down is a different undertaking. The people who have so far spent the longest time deep underwater are commercial divers who carry out construction work on oil and gas installations. They spend weeks inside pressurised capsules on ships and oil rigs, commuting each day inside a diving bell to their work site 100 metres or more below. Their bodies stay saturated with diving gases the entire time, until they are slowly decompressed at the end of each mission.
Scientists have also adopted saturation diving as a means of spending more time at greater depths. A pioneer of this was French underwater filmmaker, Jacques-Yves Cousteau, who in the 1960s built a starfishshaped underwater base in the Red Sea called Conshelf II. His grandson, Fabien Cousteau, is now planning a next generation, deep-sea facility called Proteus.
“In order for us to understand something as complex, something as mysterious, something as foreign as the ocean world, one has to spend a lot of time down there,” Cousteau said, when we spoke about Proteus on the Catch Our Drift podcast.
Dubbed the first International Space Station for the ocean, Proteus will be a larger and more adaptable version of previous underwater habitats including Aquarius in Florida – the only one still in operation and where in 2014 Cousteau spent a recordbreaking 31 days living underwater.
Eventually, Cousteau hopes there will be a network of Proteus bases through the ocean, to be used by scientists and filmmakers, as well as astronauts training for the rigours of space. The first base will accommodate a team of 12 aquanauts and is due to be
"We want people to be able to dream, to be able to connect with the ocean"
installed in a marine protected area off the island of Curaçao. It will be in around 18 metres of water, so not exactly the abyss, but still proof of concept for groups of people living and working underwater.
Proteus will even house the world’s first underwater greenhouses to grow fresh food for the crew and a broadcast studio to help communicate the wonders of the deep. “We want people to be able to dream, to be able to connect with the ocean,” said Cousteau.