Ancient Extremophiles Found Under Glacial Ice

Diatoms can be found living in a wide variety of extreme environments, including ancient Antarctic Ice. Some believe they may even exist on Europa and in interstellar dust. The above diatom, Surirella, was collected from the alkaline and hypersaline Mono Lake. Originally uploaded in Microbial Life.

For millions of years a secret has been hiding below Taylor Glacier in Antarctica’s desert waste, the McMurdo Dry Valleys. This secret is newly-discovered microbes (some of which could be similar to the one pictured above) that have been living and developing in isolation without access to sunlight or oxygen; and, breathing iron.

"Among the big questions here are: How does an ecosystem function below glaciers? How are they able to persist below hundreds of meters of ice and live in permanently cold and dark conditions for extended periods of time, in the case of Blood Falls, over millions of years?," says Jill Mikucki, lead author of the paper and research associate in the Department of Earth Sciences at Dartmouth.

These extremophiles, so-called because of their ability to survive in the most severe climates our planet has to offer, are living in a briny liquid trapped under the glacier. This brine is not dissimilar from seawater; and, given the other conditions, no one would have expected any life to survive whatsoever.

"This briny pond is a unique sort of time capsule from a period in Earth's history," says Mikucki. "I don't know of any other environment quite like this on Earth."

Much to the researchers' surprise, they discovered that while these microbes existed in isolation, they shared many similarities with microbes found in marine environments. This has lead researchers to a novel hypothesis: they believe these extremophiles are adapted remnants of a once-larger population of ocean-dwelling microbes.

"The salts associated with these features are marine salts, and given the history of marine water in the dry valleys, it made sense that subglacial microbial communities might retain some of their marine heritage," Mikucki said.

One theory says that when the sea level fell more than 1.5 millions years ago, microbes and possibly other smaller life forms, became trapped in this seawater pond. This pond eventually became covered over by the Taylor glacier trapping everything inside. Most of the other life forms would have died; but, these microbes obviously managed to adapt.

"It's a bit like finding a forest that nobody has seen for 1.5 million years," says Ann Pearson, Thomas D. Cabot Associate Professor of Earth and Planetary Sciences at Harvard. "Intriguingly, the species living there are similar to contemporary organisms, and yet quite different -- a result, no doubt, of having lived in such an inhospitable environment for so long."

Chemical analysis proves the microbes survived by breathing iron with an assist from a sulfur catalyst.

Scientists believe these microbes will provide a better understanding of Earth’s geological period when most of the world was covered in ice. Also, it opens the mind to the possibilities of life on other planets; including the ice caps on Mars; and, one of Jupiter’s moons, Europa, which is covered in ice.