At the end of Taylor Glacier in the McMurdo Dry Valleys, in Antarctica, a rusty-red stain spills across the ice and rocks before reaching Lake Bonney. It looks almost impossibly like a frozen waterfall of blood. But there is no blood, and Blood Falls is not really a waterfall at all. The color comes from iron-rich, hypersaline water emerging from beneath the glacier and turning red as the iron oxidizes when it meets the atmosphere.
The remarkable part is what lies behind that strange splash of color. Beneath Taylor Glacier is an isolated brine system containing microorganisms that survive in conditions that seem hostile to almost everything we associate with life: darkness, extreme cold, high salinity and little available oxygen. The microbes do not rely on sunlight. Instead, they obtain energy by interacting with chemical compounds involving iron and sulfur.
The brine itself is extraordinarily salty. That matters because salt lowers the freezing point of water. Researchers have found that the Blood Falls brine can remain liquid at temperatures below −7°C, allowing water to move through and beneath the glacier even when ordinary freshwater would be frozen solid.
And then there is the age of the water.
Scientists believe the brine is derived from seawater that became trapped beneath Taylor Glacier when the landscape was dramatically different. Taylor Valley was once influenced by marine conditions, and researchers estimate that the isolated system may have persisted for roughly 1.5 million years. The water has since been chemically transformed by interactions with the surrounding rock and by microbial activity.
That makes Blood Falls more than an Antarctic curiosity. It is a glimpse into an ecosystem that has existed beneath the ice, separated from sunlight and the surface world, for an extraordinary length of time. Scientists have even studied it as an analogue for environments that might exist beneath the ice of other worlds.
There is another twist. The red color isn't simply caused by iron sitting in the water. Microbial activity helps alter the chemistry of the underground system, producing iron-rich compounds that eventually emerge with the brine. Once exposed to oxygen, the iron oxidizes and stains the ice that unmistakable rusty red.
So the strange red streak at Taylor Glacier is actually the visible signature of something hidden far below: an ancient, salty environment where life has managed to persist in darkness and cold for an astonishing span of time and is exactly why scientists are so interested in it.
SOURCES
- NASA Science — Blood Falls, Antarctica’s Dry Valleys
- NASA Science — Taylor Valley, Antarctica
- NASA Astrobiology — Life at Blood Falls
- National Science Foundation — Science on the Ice
- Lyons et al., The Geochemistry of Englacial Brine From Taylor Glacier, Antarctica
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