Dark Oxygen: A New Source of Deep-Sea Oxygen Found 4,000 Meters Down

Scientists studying the Clarion-Clipperton Zone in the Pacific Ocean have documented a phenomenon now called “dark oxygen,” where polymetallic nodules on the seafloor appear to generate oxygen in total darkness. The discovery began almost a year ago, when researchers repeatedly recorded unexpected oxygen spikes while sampling the seafloor at depths around 4,000 meters. With no sunlight at these depths, photosynthesis could not explain the readings.

In 2021 and 2022, scientists enclosed small areas of the seafloor inside experimental chambers to measure oxygen levels directly. Instead of the expected decline in oxygen caused by microbial consumption, the chambers showed rising oxygen levels. This suggested that something on the seafloor was producing oxygen in the absence of light. Suspecting polymetallic nodules was involved, these potato sized rocks contain manganese, nickel, cobalt, and other metals.

Laboratory tests showed that nodules can generate small electrical currents when placed in seawater like solutions. These currents may be strong enough to split water molecules into hydrogen and oxygen, acting like natural geobatteries. Measurements showed voltage readings ranging from a few millivolts up to 950 millivolts, approaching the threshold needed for water splitting. If confirmed, this process would represent a new light independent pathway for oxygen production on the seafloor. Scientists refer to this specific mechanism as nodule-associated dark oxygen production.

The implications extend beyond basic chemistry. Polymetallic nodules are central to ongoing debates about deep-sea mining. If these nodules play an active role in oxygen cycling, removing them could alter local biogeochemistry and affect deep sea ecosystems that rely on stable oxygen conditions. Researchers note that findings come at a critical moment as international regulations for mining in the Clarion Clipperton Zone are being developed.

Dark oxygen remains an active area of investigation, but the evidence so far suggests the deep ocean may host chemical processes that have gone unnoticed for decades. For ocean science, it adds another reminder that the seafloor is not a static environment. For conservation, it raises new questions about how industrial activity could affect systems we are only beginning to understand.

Iridogorgia Chewbacca a newly named deep-sea coral that is making headlines this month, not for size or age, but for its unusual appearance. In December 2025, researchers formally described Iridogorgia Chewbacca, a rare coral species whose long, glossy, hair-like branches resemble the silhouette of Chewbacca from Star Wars. The name is now official, but the species itself has been hiding in the deep for years. The first known specimen was photographed in 2006 during a remotely operated vehicle (ROV) dive off Molokai, Hawaii, growing on a rocky slope thousands of feet below the surface. A second specimen was later collected in the Mariana Trench region, confirming that the species occupies some of the most remote and least-surveyed areas of the Pacific. These corals live in cold, dark waters where sunlight never reaches and temperature stay just above freezing. I. Chewbacca belongs to a family of deep-sea corals known for their tall, branching structures, but this species stands out. Its branches can reach up to 4ft in height, arranged in loose spirals that give the coral a shaggy, windswept look. Each branch is made up of hundreds of tiny polyps that function together as a single organism. Only two specimens have ever been collected, making it one of the rarest documented corals in its group. Corals like Chewbacca grow extremely slowly sometimes only millimeters per year which means individual colonies may be centuries old. Their presence can indicate long term stability in deep habitats, while their vulnerability highlights how easily these ecosystems can be damaged by deep-sea mining, trawling, or climate driven changes in ocean chemistry. Even with decades of ROV surveys, new species continue to appear in areas once thought barren. Iridogorgia Chewbacca may have earned attention because of its Hollywood nickname, but its scientific value is far more important. It represents another reminder that the deep ocean still holds species we’ve barely begun to study and the importance of protecting these habitats.

Scientists have documented the deepest gas hydrate cold seep ever found in the Artic, revealing a previously unknown ecosystem thriving 3,640 meters below the surface on the Molloy Ridge in the Greenland Sea. The site, called Freya Hydrate Mounds, was identified during the Ocean Census Artic Deep- EXTREME24 expedition and published in December 2025 in Nature Communications. This discovery pushes the known depth limit for gas hydrate outcrops nearly 1,800 meters deeper than any previously recorded site. Gas hydrates are ice like solids formed when methane and other gases freeze under high pressure and low temperature. They are usually found at depths shallower than 2,000 meters, so the Freya site shows they can form and remain stable in far more extreme environments than expected. The Freya mounds form a compact field of hydrate structures, collapse pits, and small ridges. ROV surveys documented active methane seepage, crude oil emissions, and a dynamic landscape where hydrate mounds appear to form, destabilize, and collapse over time. Researchers also recorded methane flares rising more than 3,300 meters through the water column, among the tallest ever observed globally. The gases at the site are thermogenic, originating from Miocene aged sediments. This indicates deep geological fluid migration over millions of years and shows that the system is shaped by tectonic activity, heat flow, and long-term environmental change. Despite the extreme depth and cold, the Freya site supports a dense chemosynthetic community. Observed species include siboglinid tubeworms, maldanid worms, snails, amphipods, and other seep associated organisms. Many of these species are also found at Artic hydrothermal vents, revealing an unexpected ecological connection between deep sea habitats once thought to be isolated from one another. Scientists say the Freya Hydrate Mounds provide an ultra deep natural laboratory for studying methane stability, deep carbon cycling, and how Artic ecosystems respond to environmental change. The findings also highlight the need to protect these habitats from future deep-sea mining or industrial activity, as they may play a critical role in the biodiversity of the deep Artic.

NASA and ESA Launch Sentinel-6B to Extend Global Sea-Level Records

NASA and its European partners have launched Sentinel-6B, the newest satellite designed to monitor global sea levels with the high precision. The mission continues a decades-long effort to track ocean height, temperature, and circulation patterns from space. Sentinel-6B lifted off on November 16, 2025, and is now in orbit as the primary reference satellite for global sea-level measurements.

Sentinel-6B is part of the Copernicus Sentinel-6/Jason-CS mission, a collaboration between NASA, ESA, EUMETSAT, NOAA, the European Commission, and CNES. It succeeds its twin satellite, Sentinel-6 Michael Freilich, which launched in 2020. Together, the pair extend a sea-level record that began in 1992 with the TOPEX/Poseidon mission and continued through the Jason-1, Jason-2, and Jason-3 satellites.

The satellite carries a radar altimeter that sends signals to the ocean surface and measures the return time to calculate sea-surface height. It also includes an advanced microwave radiometer to correct for atmospheric water vapor, improving the accuracy of sea level measurements. Sentinel-6B will map about 90 percent of Earth’s ice-free oceans every 10 days, providing consistent global coverage.

In addition to sea-level monitoring, Sentinel-6B collects vertical profiles of atmospheric temperature and humidity using radio-occultation techniques. These data help improve weather forecasting, hurricane prediction, and climate modeling. NASA notes that the satellite’s measurements also support coastal planning, flood preparedness, and long-term climate assessments.

The mission is designed to operate through at least 2030. Its data will help scientists track how quickly oceans are rising, how heat is distributed across the planet, and how ocean circulation patterns are shifting. These long-term records are essential for understanding changes in coastal risk, storm intensity, and global climate trends.

Sentinel-6B’s launch marks the continuation of one of the most important climate-monitoring efforts in Earth science. With nearly four decades of continuous sea-level data, the mission provides a clear view of how the ocean is responding to warming temperatures and melting ice. The new satellite ensures that this record will remain uninterrupted for years to come.