Scientists uncover big clue as to how Antarctica's mysterious Blood Falls came to be

Scientists uncover big clue as to how Antarctica's mysterious Blood Falls came to be Brine that feeds the gruesome-looking Blood Falls in East Antarctica may have been emplaced when sea levels were higher than they are now, a new study says. At the end of a glacier deep in East Antarctica's Taylor Valley, there is a haunting waterfall that oozes red brine like a bleeding wound in the ice. Scientists explained the brine's gory hue several years ago, finding that it is exceptionally rich in iron. And now, they may have identified the salty water's origin. Microbes in the crimson waterfall, called Blood Falls, suggest the brine is composed of ancient seawater that was trapped in a pool beneath the glacier when ocean levels fell and the glacier advanced. However, it's unclear exactly when that happened, researchers noted. Previous studies had already proposed a seawater origin for the brine, based on various chemical signatures and bacteria detected in the liquid, but the new results add molecular and genetic evidence to the mix of clues. "Findings in this study reveal a dominance of marine eukaryotic lineages in the Blood Falls area" compared with the broader region, known as the McMurdo Dry Valleys, the authors wrote in the study, published Monday (Aug. 3) in the journal Nature Geoscience. "This marine signal is less prominent but still detectable in the prokaryotic structure," the researchers added. Eukaryotes' cells contain a membrane-bound nucleus and other closed internal compartments. Prokaryotes, by contrast, are single-celled organisms whose DNA floats around freely in the cell, unbounded by a membrane. To characterize the types of microorganisms present within Blood Falls, the researchers used a suite of genetic techniques to analyze 167 samples of water, sediment and air from around the falls and the broader McMurdo Dry Valleys. Some researchers argue that Blood Falls' water does not originate from seawater, and suggest the marine bacteria and chemical signatures that point to seawater may have instead reached the falls from the ocean via intense winds, which are common in the McMurdo Dry Valleys. By analyzing samples from various sites in the Dry Valleys, the team behind the new study compared microorganisms from the wider region with those at Blood Falls to determine if Blood Falls has a distinct microbial assemblage potentially left over from ancient conditions. The researchers found that the crimson brine and associated red-tinted sediments at Blood Falls shared a higher proportion of eukaryotes with nearby oceanic samples than other sites in the Dry Valleys did. Whereas Blood Falls had a little over 9% of its eukaryotes in common with the ocean, the Dry Valleys showed only about 1% similarity, according to the study. The remaining eukaryotes and most of the prokaryotes identified in the paper had freshwater and terrestrial origins. Get the world’s most fascinating discoveries delivered straight to your inbox. The results also showed that the air near Blood Falls contained only a tiny proportion of marine microorganisms, suggesting that present-day winds can't fully explain the microbial composition of Blood Falls, the researchers wrote. RELATED STORIES - Antarctica just experienced minus 119 F, Earth's coldest temperature since 2012 — here's why - Scientists discover giant, fan-shaped structure deep beneath the East Antarctic Ice Sheet - Antarctica’s sudden sea ice loss is one of the most extreme and confusing events in the modern climate record. Scientists now know why it's happening. Therefore, an ancient seawater origin is the most likely explanation for the microorganisms found at Blood Falls today, the team concluded. Winds may have played a role in shaping the community in the past, but now, their influence is probably insignificant, the team added. The brine that feeds Blood Falls may have become entrapped more than 1 million years ago, during a warm period with higher sea levels and less ice cover than there is now, previous estimates suggested. However, further work, including more comprehensive genetic profiling and mapping of microorganisms, is needed to pinpoint when Taylor Valley's glacier grew to cover the brine, the researchers wrote. Zoumplis, A., Füssy, Z., Kaul, D., Schulte, N., Zheng, H., Lampe, R. H., Brylka, K., Venepally, P., Mikucki, J. A., McKnight, D. M. and Allen, A. E. (2026). Molecular evidence for a relict marine community in an Antarctic Dry Valleys subglacial brine-fed system. Nature Geoscience. https://doi.org/10.1038/s41561-026-02054-6 Antarctica quiz: Test your knowledge on Earth's frozen continent Sascha is a U.K.-based staff writer at Live Science. She holds a bachelor’s degree in biology from the University of Southampton in England and a master’s degree in science communication from Imperial College London. Her work has appeared in The Guardian and the health website Zoe. Besides writing, she enjoys playing tennis, bread-making and browsing second-hand shops for hidden gems. You must confirm your public display name before commenting Please logout and then login again, you will then be prompted to enter your display name.