Why Does Antarctica’s Blood Falls Spew Ruby Red Water? Microbes Offer New Clues About the Geologic Feature’s Ancient Origins

The falls contain saltwater rich with iron, which oxidizes and turns red when exposed to air. A new study provides further evidence that the brine probably comes from ocean water trapped when flood waters retreated millions of years ago

Margherita Bassi | Daily Correspondent

August 6, 2026 4:26 p.m.

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In one of East Antarctica’s dry desert valleys, a natural feature called Blood Falls occasionally spews shockingly red-orange saltwater. Flowing from Taylor Glacier into Lake Bonney, the brine is rich with iron, which oxidizes and turns rust-colored when exposed to air. The crimson is so striking that you can see it from Google Maps’ satellite images.

The bloody scene, in addition to the barren surrounding landscape, might not seem like a particularly welcoming habitat for life. New research, however, zeroes in on a complex microbial ecosystem thriving in the red-stained ice, mud and sediments and bolsters the idea that the organisms’ ancestors may have traveled far to get there.

In a study published on August 3 in the journal Nature Geoscience, researchers found a microbial community in the blood-colored material at the lowest end, or terminus, of Taylor Glacier, full of marine-associated creatures—despite their long distance from the ocean. The findings bolster the idea that the falls are fed by a long-isolated pool of marine water and shed light on microbes’ adaptability.

“Finding what is effectively a thriving marine oasis in a polar desert—more than 20 miles from the ocean—was extraordinary,” study co-author Andrew Allen, a marine biologist at the Scripps Institution of Oceanography at the University of California, San Diego, tells Popular Science’s Laura Baisas. “The diverse microbial community we found retains a biological connection to an ancient marine environment while demonstrating the remarkable resilience and adaptability of life.”

Allen and his colleagues examined 167 samples of sediment, water and air from the area, called the McMurdo Dry Valleys, as well as a nearby ice-covered inlet for reference. Genetic analyses revealed that samples collected around Blood Falls contained lots of eukaryotes—microbes made of cells with nuclei and other membrane-bound organelles—associated with marine environments. Those identified include diatoms, dinoflagellates, haptophytes and ciliates. In fact, more than 60 percent of the diatoms found in the red mud and sediment samples had ancestral ties to ocean life. Some of the sampled prokaryotes, single-celled organisms without nuclei or membrane-bound organelles, also had marine roots.

Nearby locations, on the other hand, hosted mostly terrestrial and freshwater microbial communities, pointing to something special taking place at Blood Falls.

“We think that this periodic outflow of brine water creates a habitat where marine microbes could persist,” Allen tells Scientific American’s Adam Kovac. As for how they got there, “the origin of these particular marine microbes is probably most consistent with the idea of ancient flooding than wind dispersal.”

Past research indicates that millions of years ago, when Antarctica was warmer than it is today, the ocean may have flooded its eastern region. When the waters later retreated, some may have gotten stuck beneath the encroaching Taylor Glacier around 2.5 million years ago, per a statement.

Scientists have previously discovered marine-associated bacteria, types of prokaryotes, in Blood Falls’ brine. However, some researchers suspect that ocean sediments and organisms were simply carried there by strong winds. The recent discovery of eukaryotes with ancestors that lived in the sea bolsters the idea of an ancient oceanic source for Blood Falls.

What’s more, the new study sheds light on the microbes themselves. Analyses suggest that some of the eukaryotes near Blood Falls have enrichments in cellular pathways involved in photosynthesis, stress responses, cellular repair and ability to survive in salty habitats.

The study is “noteworthy” for its evidence that these microbes “have adapted to environments that are very different from the habitats in which they evolved,” Brent C. Christner, an environmental microbiologist at the University of Florida who didn’t participate in the study, tells Smithsonian magazine. “The microbes they documented have evolved strategies to survive in the dry valleys despite conditions that differ greatly from their ancestral marine setting.”

And they haven’t just adapted to a new environment. The place they now call home is an extremely harsh habitat, showcasing the microbes’ impressive endurance.

Moving forward, the marine eukaryotes could help researchers come up with a more precise estimate for when the Blood Falls’ brine became isolated, Allen tells Gizmodo’s Ellyn Lapointe.

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.