Blood Falls: Antarctica’s Rust-Red Glacier

In 1911, Australian geologist Thomas Griffith Taylor was exploring a valley in Antarctica when he came across something strange: a bright red stain running down the white face of a glacier. The valley and the glacier were later named after him, and the red stain became Blood Falls. Early explorers guessed the color came from red algae. The real cause is beneath the ice. Millions of years ago, seawater filled a fjord in the area. About 5 million years ago, it was cut off, and scientists estimate the pool under Taylor Glacier was sealed in roughly 1.5 to 2 million years ago. Over time, the trapped water became extremely salty, two to three times saltier than the ocean, and that salt keeps it from freezing even at about 19°F. The brine carries dissolved iron. Deep under the glacier there’s almost no oxygen, so the iron stays dissolved. When the brine seeps out at the glacier’s edge and touches the air, the iron oxidizes and leaves a rust-red stain on the ice. In 2023, Johns Hopkins researchers took a closer look. Using electron microscopes, they found the color comes from tiny iron-rich nanospheres, about 1/100 the size of a human red blood cell. Earlier studies missed them because they aren’t crystals. The brine isn’t sterile either. Researchers have found at least 17 types of microbes living in it, surviving with almost no oxygen. Scientists study them as a clue to how life might survive on other worlds, including Mars.