Scientists find the origin of Antarctica’s creepy ‘Blood Falls’

The McMurdo Dry Valleys of Antarctica are some of the most extreme desert regions on the planet. But new research indicates that the region may actually be full of salty, extremely cold groundwater. The water may even connect surrounding lakes into a massive network, and it probably hosts extreme microbial life.

The findings were reported Tuesday in Nature Communications. Despite McMurdo’s apparent dryness on the surface, it’s always hinted at something more: The region is home to the magnificently creepy Blood Falls, a red ooze that shines bright against the otherwise desolate surface. For a while scientists believed that red algae gave this mysterious, bloody ooze its vibrant color. But even though iron oxide is responsible for the hue, analysis has shown that the feature does contain strange bacterial life.

Blood Falls Antartica

Scientists knew that ooze had to be coming up from somewhere, but were surprised to find just how extensive the valley’s briny waterways might be.

“I’ve been studying Blood Falls for quite some time, and it’s always been a mystery,” said lead study author Jill Mikucki of the University of Tennessee. As a microbiologist, she’s long been interested in the communities that live in the oozy brine.

A helicopter flies the AEM sensor over Lake Frxyell in the McMurdo Dry Valleys, Antarctica. (L. Jansan)


A helicopter flies the AEM sensor over Lake Frxyell in the McMurdo Dry Valleys, Antarctica. (L. Jansan)


She and her colleagues used an electromagnetic sensor mounted on a helicopter to scope out the area, testing the conductivity of the ground below. Water increases its resistivity as it freezes, meaning that it’s less conductive of electrical currents. But salty water — which can stay liquid at lower temperatures — have very low resistivity.

“We found, as expected, that there was something sourcing Blood Falls,” Mikucki said, “and we found that these brines were more widespread than previously thought. They appear to connect these surface lakes that appear separated on the ground. That means there’s the potential for a much more extensive subsurface ecosystem, which I’m pretty jazzed about.”

It’s possible that this extensive brine isn’t unique to the valley, Mikucki explained, and that subsurface ecosystems of extreme microbes might be connected to visible lakes, and perhaps even interact with the ocean.

“It turns out that as beautiful and visceral as Blood Falls is in these valleys, it’s actually just a blip. It’s a little defect in this much more exciting feature,” she said.

She hopes that the team will be able to go back and survey more areas to see just how connected the lakes of Antarctica are, and how much these subsurface brines interact with oceans at the coast. As with all work in the Dry Valleys, everything her team does is as useful for space exploration as it is for research on Earth.

“Scientists have been using the Dry Valleys to test instruments since the Viking missions,” Mikucki said. “So how we detect the brines and access them is relevant to work on places like Mars.”

And if we find life on another planet, it’s most likely going to look like the life we find in Antarctica. The subsurface lake Vostok, which is now thought to contain extensive (and quite alien) life, is often cited as an example of what might be found on Europa, Jupiter’s ice-and-ocean covered moon. Recent studies on Mars found evidence of brines on that planet, which could presumably have supported life once as well. On our planet, these subsurface waters host only the most extreme forms of life. But elsewhere in the universe, the same conditions might be as hospitable as a planet gets.

“The subsurface is actually pretty attractive when you think about life on other planets. It’s cold and dark and has all these strikes against it, but it’s protected from the harsh environment on the surface,” Mikucki said.


“We’ve learned so much about the Dry Valleys in Antarctica just by looking at this curiosity.”


“Blood Falls is not just an anomaly, it’s a portal to this subglacial world.”


Researchers suggested in the past that a deep salty groundwater system might lie beneath the Dry Valleys, known for decades to have its own permafrost and above-ground network of small frozen lakes. Mikucki and her colleagues partnered with SkyTEM, a Denmark-based airborne geophysical survey company. They used a helicopter to fly a giant transmitter loop over the Dry Valleys. The loop induced an electrical current in the ground. Then the scientists measured the resistance to the current as far as 350 meters (over 1,000 feet) below the surface.

The video clip below shows the sensor flying over Lake Bonney in the McMurdo Dry Valleys, Antarctica.

In this way, the researchers identified two distinct zones where there may be concentrated brines (salt water) below Antarctica’s ice.

The scientists say this hidden groundwater might create subsurface links between glaciers, lakes, and possibly even McMurdo Sound, part of the ocean around Antarctica into which the ice of the Dry Valleys continually flows.

The zones of underground water appear to stretch from the Antarctica’s coast to at least 7.5 miles (12 kilometers) inland. The water is thought to be twice as salty as seawater. In fact, Mikucki told the Christian Science Monitor, in her recent study:


“Salty water shone like a beacon.”


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Blood Falls in Antarctica. Photo by Benjamin Urmston via ScienceNow

Australian explorer and geologist Griffith Taylor discovered Blood Falls in Antarctica in 1911.

The Falls seep 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 later – thanks to Jill Mikucki’s 2009 study – they accepted that the red color was due to microbes from what had to be a lake hidden beneath Taylor Glacier. Lake water trickles out at the glacier’s end and deposits an orange stain across the ice as its iron-rich waters rust on contact with air.

How can the microbes that color Blood Falls survive underground, 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.


Read Mikucki and colleagues’ 2009 paper, explaining Blood Falls’ red color, in the journal Science.


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Dry Valleys and McMurdo Sound, via Wikimedia Commons and USGS

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False-color image of Taylor Glacier, flowing into Lake Bonney in Antarctica. Blood Falls is on the left side of both photos. Image acquired by NASA’s Terra satellite on November 29, 2000. Read more about this image from NASA’s Earth Observatory.

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 – 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 on the surface of the Dry Valleys. Each is chemically different from the others. Geologists who work in Antartica have studied for years to try to understand how the lakes formed and why they evolved so differently through time.

Now they will be trying to understand more about the hidden groundwater – and the ecosystem it must contain – revealed by the presence of Blood Falls.

Bottom line: The red color of Blood Falls in Antarctica was known to be caused by microbes living off sulfur and iron in what was surmised to be oxygen-free water trapped beneath the ice for nearly 2 million years. Recent work by Jill Mikucki at the University of Tennessee, Knoxville, confirms that there are indeed zones of liquid briny water hundreds of meters below Blood Falls, likely harboring a hidden ecosystem of microbial life.

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