Yellowstone_gunk-CM

Neither a painting of a rust stain nor a picture of rust, this close-up photo from one of Yellowstone National Park’s many hot springs shows thermophiles —microorganisms that thrive in hot temperatures. When bunched together, the individual organisms appear as a color but different types thrive at varying specific temperatures. The varying colors show where one thermophile ends and another begins. Many scientists believe life on earth may have begun in high-temperature environments and the first living organisms could have been thermophiles. (Courthouse News photo / Chris Marshall)