In the heart of Antarctica, where vast frozen deserts stretch endlessly, a dark-red liquid seeps from Taylor Glacier in a scene that makes the ice appear to bleed. Known as Blood Falls, it is one of the most mysterious natural phenomena on Earth.
A recent study published in the journal Antarctic Science has offered a new explanation for how the red saltwater surges to the surface, more than a century after scientists first began puzzling over the phenomenon.
Not blood, not algae
When Australian geologist Griffith Taylor discovered the site in 1911, he believed the red colour was caused by algae and named it Blood Falls. Subsequent research proved that the colour has nothing to do with blood or algae; it is instead produced by water that is extremely saline and rich in iron, trapped beneath the northern end of Taylor Glacier for at least 1.5 million years, according to Science Alert.
The water originates from an ancient pocket of seawater that became isolated beneath the ice as the glacier advanced over time, growing progressively saltier until it became a concentrated brine that does not freeze at normal temperatures.
When this water reaches the surface and comes into contact with oxygen, the iron it contains oxidises — just as rust forms — turning it the deep red colour that defines Blood Falls.
The mystery of the water's path
For decades, scientists were unable to explain how the water travelled from deep within the ice to the surface. In 2017, however, a team from the University of Alaska Fairbanks used radar to map a route extending roughly 300 metres through a hidden network of pressurised channels inside the glacier, showing that the high salinity lowers the water's freezing point, allowing it to remain liquid despite the extreme cold.
The freezing of portions of the brine also releases heat that helps warm the surrounding ice, keeping the channels open and allowing water to continue flowing.
Taylor Glacier is today considered the coldest known glacier on Earth to contain continuously flowing water.
An isolated world beneath the ice
But the greatest surprise lay not in the water's chemistry, but in the life concealed within it.
Hundreds of metres below the ice, scientists discovered an entire community of bacteria that had lived in isolation from sunlight, oxygen, and the outside world for more than a million years.
These microorganisms rely on sulphate compounds for energy, surviving in an environment that permits no known form of surface life. They have never been exposed to sunlight and have never depended on oxygen to survive.
Obtaining samples of this water required years of fieldwork before analysis revealed a microbial ecosystem of astonishing activity.
A window onto life beyond Earth
Blood Falls has become a key site in astrobiology research. Scientists believe it represents a natural model for the extreme icy environments that may exist on moons such as Jupiter's Europa or Saturn's Enceladus, where liquid saltwater could lie beneath thick layers of ice.
The surge mechanism
In the new study, researcher Peter Doran of Louisiana State University led a team that observed Blood Falls by chance in September 2018 using three instruments simultaneously: a GPS station measuring glacier movement, a camera capturing daily images of the falls, and sensors monitoring the temperature of the adjacent lake.
The measurements showed that the glacier's surface dropped by approximately 15 millimetres while its forward movement slowed by roughly 10%, coinciding with the appearance of new red patches and a sudden recorded drop in lake water temperature.
The researchers concluded that pressure gradually accumulates inside the brine trapped beneath the ice and, upon reaching a certain level, bursts outward in pulses, causing measurable changes in the glacier's surface before the cycle begins again.
A natural early-warning system
The researchers suggest that long-term monitoring of this phenomenon could help reveal changes occurring inside Taylor Glacier and may make Blood Falls an early indicator of the shifts taking place in Antarctica's glaciers.
With its unique combination of geology, chemistry, and microbiology, Blood Falls remains one of the most remarkable natural phenomena on Earth — a natural laboratory that may help scientists understand the limits of life on this planet and the possibility of its existence elsewhere in the solar system.