Source: National Geographic

Outside, the sinking sun is coloring the autumnal sky a brilliant lavender, a rich hue that lingers over a vast blanket of ice. Here, off the northern coast of Greenland, the Arctic Ocean is masquerading as land, a snowy patchwork of smooth ice floes and abrupt, jagged piles of crystalline debris. Only the subtle shifting of our ship, the Norwegian icebreaker R.V. Kronprins Haakon, betrays the landlocked illusion.

It took longer than expected to get to this icy wonderland from the small coal-mining town of Longyearbyen, the most populated port in Norway’s Svalbard archipelago. Now that we’re here, Chris German isn’t paying much attention to the dramatic seascape. Instead, he’s staring intently at a live feed of the seafloor, and he’s trying on hats. Every 10 minutes or so, he plops a different hat on his head, rotating through haberdashery that includes a faux sealskin ushanka, a woven orange fez, and a beanie from the Woods Hole Oceanographic Institution, where he works.

The costume changes help German pass the time while we wait for the first glimpse of our quarry: a broken patch of seafloor that’s pumping smoky, superheated fluids into the darkness, perhaps helping to power one of the most alien ecosystems on Earth. This elusive zone is called the Aurora hydrothermal vent field. It’s the most northerly vent field yet known, and it’s among the deepest in the world, sitting nearly 2.5 miles below a permanent covering of sea ice.

Listen to National Geographic Explorer Kevin Hand talk about how deep-sea exploration fuels the search for alien life on our podcast, “Overheard at National Geographic.”

Exploring the deep sea, like venturing into deep space, is a high-risk endeavor. The abyssal seafloor is an unforgiving place for even the hardiest robots, and this mission has seen its share of mishaps, including a few heart-stopping days when it seemed like the team had lost its main underwater rover to the freezing polar ocean.

But on this violet evening, after hours of drifting over a muddy seafloor, a high-resolution camera towed beneath the ship at last passed directly over a gaping maw in Earth’s crust. Beamed onto screens throughout the ship, the footage revealed an angry black plume erupting from a crater measuring nearly five feet across—an astonishing span for this flavor of undersea smoker.

“That is a big f***ing plume,” German said, his rotating headgear paused on the ear-flapped ushanka. “This is a lot more than we knew was here.”

Studying vents below the ice

On September 19th, the research vessel, Kronprins Haakon, departed Longyearbyen, Svalbard headed toward the Aurora hydrothermal vent field, located along the Gakkel Ridge some 4000 meters below the arctic ice. After several days meandering through thick sea ice, the vessel reached its destination on September 28.

Later that night, the same camera would fly over the site twice more; and multiple passes over the next week would reveal wildly rugged terrain populating the southern slope of the Aurora seamount. The images revealed that the vent field is covered with extinct chimneys, heaps of extruded minerals, and not just one, but at least three black smokers.

The results offer our best look yet at such an exotic, ice-shrouded ecosystem. Better understanding this remote biosphere could help scientists figure out how creatures move through Earth’s deep oceans, and whether Arctic waters form a pathway for animals moving between the Atlantic and Pacific basins.

“The idea is to really understand this area when it’s still pristine,” says deep-sea ecologist Eva Ramirez-Llodra, the project’s lead scientist from the Norwegian Institution for Water Research. “If climate change gets rid of the ice, this will become a more used route to go to the Pacific, and it could become an open area for potential mining, for fisheries … it’s good to know what’s there.”

What’s more, the Aurora vents could hold the keys to detecting life-forms in the deep oceans on alien worlds. For now, Aurora is one of the closest Earth-analogs to the seafloor vents that are thought to be erupting on faraway ocean worlds, including the ice-encrusted moons Europa and Enceladus, which are considered among the best places to look for existing extraterrestrials.

“Alien oceans beyond Earth are so compelling in the search for life elsewhere,” says National Geographic Explorer Kevin Hand, an astrobiologist at NASA’s Jet Propulsion Laboratory who took part in the Aurora expedition. “Wherever we’ve looked on planet Earth and found liquid water, we’ve found life.”

Plethora of vents

In general, oceanic hydrothermal vents arise when seawater seeps through cracks in Earth’s crust and mingles with hot rocks beneath the surface; those buried molten rocks heat the saltwater and fuel chemical reactions that erupt in a roiling mass through vents in Earth’s crust. The continual extrusion of mineral-rich, superheated seawater provides the heat and energy needed for some organisms to thrive in these cold, dark depths, including a menagerie of vent-specific gigantic tube worms, foot-long clams, blind shrimp, and extreme microbes.

For a long time, canonical wisdom had suggested that hydrothermal vent activity could only exist at the fastest spreading mid-ocean ridges—places like the East Pacific Rise, where Earth’s tectonic plates are hustling away from one another at speeds of around seven inches a year. At these bursting planetary seams, the brisk spreading of Earth’s crust means that fresh magma is always available to fuel the vents.

Over the years, though, German and his colleagues have found vents populating a variety of ridges, including some that languidly go their separate ways. Our most recent target, the Gakkel Ridge, is a volcanic rift bisecting the Arctic Ocean that is spreading at the stultifying rate of less than half an inch a year.

“Nowhere is precluded from having hydrothermal activity,” German says. “We can dispense with that myth now.”

Scientists first went prospecting for hydrothermal plumes along the Gakkel Ridge in 2001. During that cruise, a layer of murky water detected near the seafloor hinted at vent activity, and a rock-dredge pulled up the remains of an extinct chimney. Both observations could be explained by black smokers, the sort of vents that launch towers of dark, hot plumes into the water.

During a second cruise in 2014, German and his colleagues returned to Aurora aboard the icebreaker Polarstern. They searched for vents by looking for hydrothermal signatures in the water column and, toward the end of the cruise, they dropped a high-resolution camera into the deep. Just two hours before it was time to head home, the team caught their first glimpse of a small chimney, a fleeting photobomb by a smoking vent that slid into the margins of several frames.

But the vent signatures written into the freezing sea suggested that something much more massive must lie below. Buoyed by that discovery, this year’s expedition, known by the acronym HACON, aimed to put the Aurora vent field into context. How extensive is the entire system? What kind of chemistry is involved? Can the vent support a deep-sea ecosystem, and if so, what kinds of organisms live there?

And, for the astrobiologists on board, what insights might the site bring in efforts to detect life on ice-covered ocean worlds across the solar system?

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Source: National Geographic