Blood Falls: The Antarctic Glacier That Bleeds

In 1911, during Robert Falcon Scott’s Terra Nova expedition, geologist Griffith Taylor led a party into one of the ice-free McMurdo Dry Valleys. At the end of the glacier that now carries his name, where it meets frozen Lake Bonney, they found the white ice cliff streaked a deep rust red. Taylor later wrote that “bright red alga lent an unusual touch of colour” at the snout of the glacier. The stain was soon known as Blood Falls.

Not algae

Algae was a fair guess in 1911, but it was wrong. When scientists came back in the 1960s they found a very salty, iron-rich liquid seeping out of cracks in the glacier front. By 1979 researchers had noted that fresh outflow carried no red at all. The liquid comes out clear, and only turns rusty once its dissolved iron meets the air. The flow is not steady. It comes in episodes, and the size of the stain changes from year to year.

Life in the dark

The bigger surprise was what lives in the brine. Jill Mikucki spent several seasons waiting for an outflow before she could catch the liquid as it ran out of a crack. “When I started running the chemical analysis on it, there was no oxygen,” she told the Harvard Gazette. Her team’s 2009 paper in Science described an active community of microbes, related to sea-water bacteria, living in a salty pool under the glacier with no light and no oxygen. They get energy by working iron and sulfur from the bedrock. The team estimated the pool was sealed off when the glacier covered it 1.5 to 2 million years ago. The salt itself points to the sea: the brine has the same ratios of salts as seawater, a leftover from when the valley was a fjord, concentrated as it froze.

How it stays liquid

The average air temperature at the glacier is about −17 °C, far too cold for ordinary meltwater. In 2015 a team flying an electromagnetic sensor under a helicopter mapped brine spreading beneath the glacier and the valley floor, part of a much bigger underground system. In 2017 a radar survey on the glacier itself traced a band of brine running through the ice toward Blood Falls. That study found the brine stays liquid because of its salt and because freezing part of it releases heat that keeps the rest flowing.

The last piece: why red

One question was left. Earlier studies assumed the red came from a rust mineral, but tests kept failing to find one. A 2022 study in Frontiers in Astronomy and Space Sciences, with Johns Hopkins microscopist Ken Livi and Mikucki among the authors, looked at Blood Falls sediment under an electron microscope. They found tiny iron-rich spheres, about a hundredth the size of a human red blood cell, mixed with silicon, calcium, aluminum and sodium. The spheres are not crystals, which is why mineral tests missed them. “As soon as I looked at the microscope images, I noticed that there were these little nanospheres and they were iron-rich,” Livi told the Johns Hopkins Hub in 2023.

Sources

• Mikucki, J. A., et al. (2004), “Saline discharge at the terminus of the Taylor Glacier, Antarctica”, Annals of Glaciology 39: montana.edu (PDF)
• Mikucki, J. A., et al. (2009), “A contemporary microbially maintained subglacial ferrous ‘ocean’”, Science 324, 397–400: doi.org/10.1126/science.1167350
• Harvard Gazette, “Microbes thrive under Antarctic glacier” (Apr 2009): news.harvard.edu
• Mikucki, J. A., et al. (2015), “Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley”, Nature Communications 6, 6831: nature.com
• Badgeley, J. A., et al. (2017), “An englacial hydrologic system of brine within a cold glacier: Blood Falls, McMurdo Dry Valleys, Antarctica”, Journal of Glaciology 63, 387–400: doi.org/10.1017/jog.2017.16
• Sklute, E. C., et al. (2022), “A multi-technique analysis of surface materials from Blood Falls, Antarctica”, Frontiers in Astronomy and Space Sciences: doi.org/10.3389/fspas.2022.843174
• Johns Hopkins Hub, “Seeing red: Researchers uncover the century-old mystery of Blood Falls” (26 Jun 2023): hub.jhu.edu

Original text. Images: U.S. National Science Foundation photographs and diagram (public domain), self-hosted. Every image on this page is credited where it appears.

Weighing it

Nothing here is supernatural, but the real story is stranger than the 1911 guess. A pool of ancient seawater, trapped under a glacier for perhaps two million years, still supports living microbes and leaks out as a red stain. Each step, from iron to microbes to liquid brine in frozen ice to the nanospheres, rests on published, peer-reviewed work. The map pin is at the level of Taylor Valley.