“It was like descending on another planet”: what the first scientists found to go down to the 8,000 meter depth of the Atacama Trench

For years, the Chilean oceanographers Osvaldo Ulloa and Rubén Escribano had imagined in their conversations what the alien landscape of the Atacama Trench would be like, that impressive crevasse that falls more than 8,000 meters deep off the coasts of Chile and Peru and that no human being had seen directly.

Ulloa and Escribano, director and deputy director respectively of the Millennium Institute of Oceanography at the University of Concepción, in Chile, had resigned themselves to studying the Trench from the surface.

Together with his team, they had mapped part of the topography of the Trench for the first time. During the Atacamex Expedition in 2018 they had taken some photos, videos, water samples and DNA of the strange creatures that inhabit the bottom of this underworld.

Since reaching those ultra-depths is technically more or less like going to the Moon, dreaming of being an eyewitness to your object of study was never an option… Until now.

Both scientists descended on the site last week with the expedition of the American explorer Víctor Bishop, who in 2019 became the first person to visit the five deepest points in the five oceans piloting a purpose-built submersible.

Ulloa, Escribano and Vescovo are the first human beings to descend into the Pit.

Each of the two trips lasted a total of ten hours, for which the aquanauts literally had to dehydrate themselves the night before, bring warm clothing, and make sure to pack a sandwich.

In two separate dives, Ulloa first and Escribano then boarded together with Vescovo a very small titanium sphere covered by a thick protective coating of synthetic foam.

Named the Limiting Factor, in honor of the fictional novels of Ian Banks, the submersible is the technological marvel that is routinely opening the doors to the exploration of the so-called hadal zone of the oceans, that is, everything below 6,000 meters.

“This was the adventure of my life and a peak in my career as a researcher in marine sciences,” Ulloa, 60, told BBC Mundo, minutes after that dive and already on the Pressure Drop mother ship.

Silence and music at the bottom of the sea

“The inside of the sphere is dark gray, it has two comfortable chairs, and it’s lined with oxygen tanks and switches for all the electronics. In the lower part there are three porthole windows that allow a view of the seabed. I was impressed by the smoothness of the crossing, and the silence, only interrupted by communications with the surface”.

The descent to the deepest point of the pit —8,069 meters, according to the maps that had been made the day before, took them three and a half hours. Ulloa imagined that he was going to get bored, but between moments of conversation with Vescovo, they ended up listening to music.

Ulloa played a song by the Chilean singer-songwriter Manuel Garcia doing a duet with My Laferte, and showed Vescovo photos of his children, who live in Sweden. In turn, Vescovo chose Tequila Sunrise, from the group The Eagles, and told him about his motivations for ending up exploring the depths. Then, between laughs, they decided that when they returned they would have time to see a piece of the Spanish series El Cid. So it was.

At some point during the descent they ate half their sandwiches: tuna for Vescovo and egg salad for Ulloa.

Once at the bottom, Vescovo maneuvered the spacecraft over an amazing terrain of valleys, ridges and other rock formations that will yield important information regarding the characteristic geology of this region of the planet.

“We were also struck by the large number of sea cucumbers, a species of sea cucumber that has been found in other trenches, but which were present in great abundance here,” says Ulloa.

“But if there is one thing that I, as a microbiologist, wanted on this expedition, it was to find tapestry of microbial colonies. And for that reason, seeing them with my own eyes was something extraordinary, the confirmation for the first time of their existence in the Atacama Trench and at more than 8,000 meters”.

Worms architects of cities

For Rubén Escribano, 64, the experience, two days later, was just as intense.

Since his interest is fauna, Vescovo descended only to 7,330 meters, exploring the eastern slope of the trench in search of more abundant organisms.

They found unexpected creatures for such depths like cold-water corals and a lone starfish. They were also able to observe animals present in greater numbers than in any other trench studied so far, including polychaete worms, amphipod crustaceans, and other hadal beings that are only now beginning to be studied.

“They told me that we had to study the pit, but they didn’t tell me that we had to go to it,” Escribano joked as soon as he got out of the submersible and stepped onto the deck.

“It was something magical; like descending on another planet and seeing the structures built by these beings. I imagined that they were tiny cities made by the worms and crustaceans that make paths in the sediment.”

The Atacama Hadal Expedition also made high-resolution maps of various stretches of the Atacama Trench, which, at 5,900 kilometers long, is one of the longest cracks in the deep ocean, a formidable structure that is born where the Nazca plate sinks under that of South America, which causes the earthquakes and tsunamis that hit this region.

The maps will be key to determining the optimal place to install the sensors of a future project to establish the first observation system anchored in the deep ocean, a titanic effort in the making by the Chilean scientific community.

Studying how the physical, geochemical and biological conditions present in the area change over time would provide the scientific basis that can be used to eventually observe the effects of climate change at high depths and better understand the processes that cause large earthquakes and tsunamis in the region.

“We have had unique access to making a leap in Chilean oceanographic science, and I am confident that this achievement will inspire new generations,” said Ulloa.

For its part, Vescovo says it is committed to the effort to continue mapping tens of thousands of square kilometers per month to support the GEBCO 2030 initiative, which seeks to complete the mapping of the entire seabed by 2030. (I)