In 1911, Australian explorer and geologist Griffith Taylor discovered a strange glacial feature in Antarctica, which is now known as Blood Falls. It’s a bright red waterfall, nearly five stories high, seeping through a crack in what’s now called Taylor Glacier, which flows into Antarctica’s Lake Bonney. Geologists first believed that the color of the water came from algae, but today the red color is known to be caused by microbes living off sulfur and iron in oxygen-free water trapped beneath the ice for nearly 2 million years. The hidden lake beneath Taylor Glacier sits beneath a quarter mile (400 meters) of ice and trickles out at the glacier’s end. It deposits an orange stain across the ice as its iron-rich waters rust on contact with air.
The subglacial lake beneath Taylor Glacier is thought to have been part of an ancient marine fjord system that became trapped as Taylor Glacier enclosed it between 1.5 million and 2 million years ago.
The sporadic outflow of reddish fluid – Blood Falls – let researchers explore the lake without drilling or risking contamination of the trapped lake itself.
Geomicrobiologist Jill Mikucki, now at Dartmouth College, published what’s still accepted as the best explanation for Blood Falls in 2009. She collected water samples from Blood Falls over a period of 6 years. A battery of tests revealed that its waters contained almost no oxygen and hosted a community of at least 17 different types of microorganisms. How could they have survived for so long, with no light or oxygen? According to a 2009 story in ScienceNow from the AAAS:
Mikucki and her team uncovered three main clues. First, a genetic analysis of the microbes showed that they were closely related to other microorganisms that use sulfate instead of oxygen for respiration. Second, isotopic analysis of sulfate’s oxygen molecules revealed that the microbes were modifying sulfate in some form but not using it directly for respiration. Third, the water was enriched with soluble ferrous iron, which would happen only if the organisms had converted ferric iron, which is insoluble, to the soluble ferrous form. The best explanation … is that the organisms use sulfate as a catalyst to ‘breathe’ with ferric iron and metabolize the limited amounts of organic matter trapped with them years ago. Lab experiments [had] suggested this might be possible, but it [had] never been observed in a natural environment.
The image above is a wider view, via satellite, of the area in Antarctica where Taylor Glacier and its Blood Falls flow into Lake Bonney. This region – known as the McMurdo Dry Valleys – is a series of parallel valleys between the Ross Sea and the East Antarctic Ice Sheet. Note the lack of snow on the surface. A nearly relentless katabatic wind — cold, dry air that rolls downhill toward the sea from the high altitudes of the ice sheet – sweeps the ground free of snow and ice. There are many ice-covered lakes in the Dry Valleys. Each is chemically different from the others. Geologists who work in Antartica are trying to understand how the lakes formed and why they evolved so differently through time. Read more about the image above from NASA’s Earth Observatory.
Bottom line: Blood Falls seeps from Antarctica’s Taylor Glacier. The red color is known to be caused by microbes living off sulfur and iron in the oxygen-free water trapped beneath the ice for nearly 2 million years.