“Blood Falls,” a rust-red cascade in Antarctica’s McMurdo Dry Valleys region, has puzzled researchers for more than a century. Multiple outlets report that the phenomenon is not caused by blood. Instead, the red color comes from iron-rich water emerging from beneath the Taylor Glacier. The flow is linked to an ancient, sub-glacial reservoir estimated to be about 1.5 million years old, trapped under the glacier. Water moves from this hidden lake to the surface through small fractures or cracks in the ice. When the iron-bearing water reaches the atmosphere, it reacts with oxygen and oxidizes, producing the distinctive red or rust hue seen in the waterfall-like stream. Scientists are studying how the trapped water travels and transforms, using the site to better understand glacial history and melt-and-flow processes under ice. The findings also contribute to broader research questions, including what kinds of chemical environments might support life in similarly icy, subsurface settings such as on other moons.