Hydrothermal vent site in the Arctic could provide clues about extraterrestrial life

In 2014, researchers at the Woods Hole Oceanographic Institution (WHOI) discovered a hydrothermal vent in the Arctic Ocean and called it the Aurora hydrothermal system. A follow-up expedition to the site, five years later, has revealed that the hydrothermal system could hold clues to finding life on other planets and their moons, a press release said.

Hydrothermal vents on ocean floors aren't a new thing. Oceanographers can list hundreds of such vents in each major ocean of the world. Therefore, when the WHOI researchers found the Aurora Hydrothermal vent, they returned, assuming it to be one more such vent with a massive ice cover.

However, a follow-up visit to the site revealed much more about the vent and how it could help scientists look for signs of life on Jupiter's moon Europa and the Saturnian moon Enceladus since they post boast subsurface oceans.

What do we know about the Aurora hydrothermal system?

Apart from being located in the Arctic region, the Aurora hydrothermal system is also unique because it is more than 328 feet (100 m) wide. This is unusually large since the vent is volcanically hosted, and comparable to tectonically hosted systems that assume such sizes.

Compared to other volcanic "black smoker" vents that are basalt hosted, the plumes from the Aurora vent have higher methane values and resemble high-temperature ultramafic-influence vents. Ultramafic rocks are primitive rocks present in the Earth's interior and whose composition resembles that of meteorites.

Ultramafic rocks are also found at slow-spreading ridges, such as the Gakkel Ridge rift valley that moves at about half an inch (one cm) every year and is home to the Aurora hydrothermal system.

How can the hydrothermal vent help us?

Oceanographers may have plotted hundreds of black smoker vents on the sea floor, but most of these interact with the basaltic or silica-rich rocks underneath. Ultramafic rocks and hot water circulation from them is an important concept in origin-of-life and astrobiology research.

Even after years of research, scientists just have composition details of less than 12 such hydrothermal vents and do not know if others have similar chemistries or ones that are significantly different from what we know. Although the Aurora system bears a resemblance with another underwater hot spring, scientists know of, they would like to study it more to know if it can expand their knowledge about such vents.

In addition to providing clues about signs of life, these vents are also sites of economic interest with high levels of copper and gold found in Aurora's deposits. Until recently, scientists were of the view that such sites would not be able to sustain the growth of mineral deposits for very long. However, it seems that these minerals might be more abundant at ridge crests than previously thought.

"We continue to be surprised by how diverse and wonderful the seafloor is. Every time we go out and explore, we get surprised because we do not just find more of the same," said Christopher German, senior scientist at WHOI in the press release. "Rather, we continue to find completely new things, different from everything we have seen before."

The research findings about the Aurora hydrothermal system were published recently in the journal, Nature Communications.

Abstract:

The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH4/Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges. We hypothesize that deep-penetrating fluid circulation may have sustained the prolonged venting evident at the Aurora hydrothermal field with a hydrothermal convection cell that can access ultramafic lithologies underlying anomalously thin ocean crust at this ultraslow spreading ridge setting. Our findings have implications for ultra-slow ridge cooling, global marine mineral distributions, and the diversity of geologic settings that can host abiotic organic synthesis - pertinent to the search for life beyond Earth.