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The Dartmouth
July 15, 2025 | Latest Issue
The Dartmouth

Microbes found below glaciers in Antarctica

The rust-colored brine that oozes from Blood Falls at Taylor Glacier in Antarctica may shed light on how early life on Earth developed in extreme conditions, according to a study led by Jill Mikucki, a geomicrobiologist and visiting fellow at the John Sloan Dickey Center for International Understanding. The study, "A Contemporary Microbially Maintained Subglacial Ferrous 'Ocean,'" was published in this month's issue of Science and highlights the discovery of microorganisms that live in the extreme environment below the glacier and are believed to cause the phenomenon at Blood Falls.

Mikucki, along with colleagues at Harvard University and elsewhere, found that the rust-colored fluid results from metabolic processes performed by microorganisms able to survive in the subfreezing, dark, oxygen-poor and salt-rich environment. The microbes use iron and sulfur compounds present in their environment to convert organic compounds into energy. During this process, iron is chemically reduced into another form and released back into the surrounding salt water, according to the study.

The iron-rich salt water is then released to the surface of the glacier, although researchers do not fully understand the mechanisms controlling this process. The iron compounds are oxidized in the air and then assume the reddish hue that characterizes the rust-colored ooze, the study suggests.

The presence of thriving microbial communities in subfreezing, dark and oxygen-poor saltwater indicates how life may have existed in similar environments during the Neoproterozoic Era, approximately 750 to 550 million years ago, Mikucki said in an interview with The Dartmouth.

Studying how microorganisms survive in extreme circumstances, inhospitable to most modern life, provides a deeper understanding of how ancient life forms performed important metabolic processes when the chemical makeup of the ocean and atmosphere was very different, she said.

The discovery may also have implications for the search for life on other planets, Mikucki said. Understanding how microbes survive in glacial environments on Earth could apply to subfreezing environments of other planets, including the ice caps of Mars, she said.

Mikucki said she first became interested in studying the Blood Falls geological system in graduate school, when she saw a picture of the area during a glaciology class, she said. Mikucki said she suspected immediately that the high iron content of the brine resulted from microbial metabolism, though at the time, scientists attributed the phenomenon to non-biological processes.

"People said there wasn't life," she said. "The paradigm has shifted. People now see glaciers as ecosystems."

Mikucki conducted much of her investigation of Blood Falls during her years as a postdoctoral fellow at Harvard University, when she made several field trips to Antarctica to collect samples of the brine.

With other researchers, Mikucki performed isotope measurements and functional gene analyses to determine the metabolic pathways involved in forming the brine.

While some of the tests were performed in laboratories in the United States, others were completed at the collection site in Antarctica, Mikucki said.

The research team developed analytic methods on the spot to respond to environmental challenges and the time constraints involved with some of the measurements, she said.

Mikucki said she hopes to investigate other aspects of subglacial environments.

"I think that it's the tip of the iceberg," Mikucki said. "There's so much we still don't understand about what's going on. I'm definitely keen to continue studying polar and subglacial environments."