Over 110 years ago, geoscientist Griffith Taylor discovered a unique waterfall during an expedition to Antarctica. The clear meltwater flowing from beneath the Taylor Glacier turns blood-red when it comes into contact with air.
The Blood Falls have puzzled scientists since their discovery. In 2017 a research team using a special ground-penetrating radar discovered that a network of fissures in the bedrock and tunnels in the ice form a buried saltwater reservoir feeding the waterfall at the glacier’s snout. The salt concentration, in combination with the pressure at the glacier base, keeps the water flowing despite the low temperatures. But what caused the sudden color change remained a mystery. In most cases, the reddish color of rocks or springs is caused by weathering of iron-rich minerals, like magnetite, goethite or hematite (also known as bloodstone). Studies conducted in the 1960s claimed to have found only very small traces of such minerals in water samples from the Taylor Glacier, not enough to explain the blood-red coloration. Another possible explanation involved a mass proliferation of red ice algae in the melting glacier, but even if traces of carbon were found, no algae were confirmed.
A research team led by the University of Alaska Fairbanks and Colorado College solved this apparent mystery by using a combination of analyses techniques. The authors studied water and soil samples taken from the Blood Falls under a Transmission Electron Microscope (TEM). TEMs can magnify objects up to 2 million times.
The researchers discovered tiny spheres just a few nanometers (the billionth part of a meter) in diameter floating in the water. A chemical analysis using X-rays showed that these nanospheres are composed of iron, silica, calcium, aluminum, sodium and other elements. Previous studies missed them as they are very small and don’t possess a crystalline structure, and most standard analytical methods used by mineralogists will miss such amorphous materials.
The study concludes that iron plays a role in the color change of the Blood Falls, but not as previously assumed. Not free iron atoms or iron-rich minerals react with oxygen, but the iron in the nanospheres will form iron-oxides and -hydroxides as soon as the meltwater comes into contact with air. Additionally, the high salinity and the presence of other elements, such as chlorine, magnesium and sodium, may play an important role in forming yellow- to orange-colored iron-phases, resulting in a blood-like coloration.
The study “A Multi-Technique Analysis of Surface Materials From Blood Falls, Antarctica” was published in Frontiers in Astronomy and Space Sciences (2023).