Beneath cold, high-pressure oceans, water and gas molecules clump together into crystalline solids called gas hydrates. During a research cruise around the North Pole, scientists encountered the deepest gas hydrate ever found—an elusive crack on the seafloor hosting a myriad of scientific treasures.
The Freya Hydrate Mounds lie under Molloy Ridge near Greenland and were discovered in May 2024. Located at a depth of nearly 12,000 feet (3,640 meters), the mounds are the deepest vents of their kind ever discovered. What’s more, the team spotted a staggering 10,000-foot-tall (3,300-meter) methane gas flare rising through the water column, another record-setting observation.
“We found an ultra-deep system that is both geologically dynamic and biologically rich,” Giuliana Panieri, study lead author and a geoscientist at Ca’ Foscari University in Italy, said in a statement. “This discovery rewrites the playbook for Arctic deep-sea ecosystems and carbon cycling.”
A paper on the discovery was published on December 17 in Nature Communications.
Cold, submerged vents
The newly found Freya Hydrate Mounds are gas hydrate cold seeps. Like hydrothermal vents, cold seeps typically appear as fissures on the seafloor that leak fluids rich in hydrocarbons. The two features have some similarities but differ in important ways.
For instance, cold seeps, true to their name, are relatively colder and emit oil and methane in addition to hydrocarbons. They’re also longer-lasting than hydrothermal vents, which are typically volatile and short-lived since they’re formed by volcanic activity.
Theoretically, there is no depth limit for how far down a cold seep can maintain stability. However, before Freya, researchers hadn’t found any seep deeper than around 6,500 feet (2,000 meters). So, at a “staggering depth” of roughly 12,000 feet, the Freya mounds “challenge our previous understanding of hydrate formation,” the researchers said.
No sunlight, no problem
Because cold seeps persist for a long time, a rich array of marine creatures make a home for themselves near the fissure. Accordingly, the researchers identified chemosynthetic communities—tiny creatures that live on chemicals, not sunlight—thriving near the cold seep, such as tubeworms, snails, and amphipods.
Surprisingly, many creatures found living near cold seeps were related biologically to those residing near hydrothermal vents, the researchers noted. This connection will be critical to consider when forming future conservation plans, they added.
An ‘ultra-deep natural laboratory’
But that wasn’t all. When the team aged the thermogenic gas and crude oil from near the crack, it found that the soil was most likely from the Miocene—so about 5 to 23 million years ago. But the mounds to this day “appear to form, destabilize, and collapse over time,” the researchers explained.
“These are not static deposits,” Panieri said. “They are living geological features, responding to tectonics, deep heat flow, and environmental change.”
This dynamic sequence makes the region an “ultra-deep natural laboratory” to study the interplay between geology and biology in the Arctic—a critical, threatened, yet poorly understood part of the planet, they concluded.