The distinctive color of the Blood Falls comes from the high iron content of the salty water, which leaves a crimson stain on the white snow as it flows out from under the glacier. That tells us this place may be preserving traces of an older connection between the Dry Valleys and the sea.” Even though glaciers are made of water ice, Antarctica’s McMurdo Dry Valleys are not just some of the planet’s coldest deserts, but also the driest. “We were not just asking whether marine organisms were present,” Zoumplis said. In the Blood Falls samples, the team’s analysis revealed between 60% and 80% of the diatoms were marine-associated.