A new study about Earth's northernmost seafloor hydrothermal system shows even more variety in vent styles than previously thought.
This has important implications for understanding the origin of these vents and assessing the global-scale impact of hydrothermal activity on the ocean and Earth system, according to the journal article, "Ultramafic-influenced submarine venting on basaltic seafloor at the Polaris site, 87°N, Gakkel Ridge," published in Earth and Planetary Science Letters.
In addition, the study has implications for understanding and investigating for habitability and perhaps even life on ocean worlds in our outer solar system, according to the study's authors.
The article reports on results from return studies in 2016 and 2023 to the Polaris hydrothermal field on the ultraslow-spreading Gakkel Ridge in the Arctic Ocean. Initial reports about the Polaris site suggested that it was a volcanically-hosted "black smoker"-type system, because of temperature and turbidity anomalies in its hydrothermal plume and because of its location near the summit of a volcanic seamount situated astride the spreading-ridge axis.
However, a combination of geochemical analyses and seafloor surveys discerned that Polaris is not a conventional black smoker hydrothermal system, but instead, discharges metal-poor hydrogen- and methane-enriched fluids into the Arctic Ocean.
Of the more than 30 locales at which deep-sea hydrothermal plumes have been detected along ultra-slow spreading mid-ocean ridges [MORs] to date, the nature of more than 90% has only been inferred from water column plume signals coupled with seafloor mapping and/or petrologic sampling. Where detailed studies have been carried out, "a diversity of styles of venting has been found, beyond what had previously been reported. This expansion of the geodiversity of hydrothermal sites has continued into the Arctic Ocean, first with the Aurora hydrothermal field [in the Gakkel Ridge] and now with this study."
"Hydrogen-rich vents like Polaris have a lot more chemical potential energy available for life than any other kinds of vents, bang per buck. The microbial diversity you get when there is that much energy available also is really quite impressive and distinct from most ordinary hydrothermal vents," said journal co-author Chris German, senior scientist in the Department of Geology and Geophysics at the Woods Hole Oceanographic Institution (WHOI).
"The discoveries we have made here are particularly important because they reassure us that we could go and search for life on other ocean worlds beyond Earth in a credible and meaningful way, based on what we now know," added German, who also is principal investigator for the Exploring Ocean Worlds project, which is a cornerstone for NASA's Network for Ocean Worlds program. German added that findings from Polaris also underscore the need for improved approaches for exploring hydrothermal plumes on Earth to properly classify their underlying sources.
"It is both fascinating and inspiring to study seafloor geologic processes in the Arctic Ocean, one of the least-explored places on Earth," said journal article lead author Elmar Albers, a postdoctoral investigator in the Department of Geology and Geophysics at WHOI. Albers' work over the past two years has been supported by a Feodor Lynen Postdoctoral Fellowship from the Alexander von Humboldt (AvH) Foundation, hosted by Chris German at WHOI. "The insights we gained from the Polaris hydrothermal system were unexpected, with major implications for hydrothermal exploration in other oceans. We are excited to learn what other surprises the Arctic holds in the future."
"Understanding the distribution of life in the universe starts here at home in exploring the places and ways that life thrives on Earth," said Becky McCauley Rench, Astrobiology Program Scientist at NASA headquarters. "The work of this team amplifies the importance of expanding our knowledge of our home planet and applying those lessons as we search the solar system and universe for answers about whether we are alone. What we learn here, in the Arctic or anywhere on Earth, is directly applied to our successful exploration at other worlds, like Europa and Enceladus, and beyond."
This work was funded primarily through NASA's PSTAR program at WHOI and by the Alexander von Humboldt Foundation, the Helmholtz Association and the Max Planck Society in Germany.
