Yellowstone's Rainbow Colors Come From Heat-Loving Microbes

The vivid oranges, yellows and greens around Yellowstone’s hot springs are alive. The U.S. National Park Service explains that many of the bright colors found in the park’s hydrothermal basins come from thermophiles, microorganisms that thrive in hot temperatures. The name means heat lover. Individually they are too small to see, but so many are grouped together, trillions of them, that they appear as mats of color. Each kind has a narrow range. Different types of thermophiles live at specific temperatures within a hot spring and cannot tolerate much cooler or warmer conditions, so the colors change in bands where one group reaches its limit and another takes over. They live in conditions extreme to human life, from near-boiling water to acidity that can burn holes in clothing. Not every color is biological: the intense blue of some springs comes from sunlight in deep, clear water.