Microbes Living in Complete Darkness
Deep beneath the rocky canyons of southern New Mexico, a network of 119 caves holds a surprising secret. Cave biologist Hazel Barton discovered green microbes thriving in areas with no sunlight. “The wall was bright green, the most iridescent green you’ve ever seen, yet it was completely dark,” Barton said. These organisms are cyanobacteria, single-celled life forms related to bacteria, usually dependent on sunlight for energy.
The Carlsbad Caverns Mystery
The caves, part of Carlsbad Caverns National Park, formed 4 to 11 million years ago through sulphuric acid dissolving limestone. The park’s main attraction, Carlsbad Cavern, draws nearly 350,000 visitors annually. While most tourists explore the Big Room with its glittering stalactites.
In 2018, microbial biologist Lars Behrendt invited Barton to join him on an expedition. As they ventured past the tourist trail, they entered pitch-black sections of the cave. When Behrendt shone a torch on the walls, green pigment appeared. Tests confirmed cyanobacteria were present, but these microbes were unlike any other—they could photosynthesize without sunlight.
Near-Infrared Light Powers Photosynthesis
Unlike regular cyanobacteria, these cave microbes contain special chlorophyll types, d and f, capable of absorbing near-infrared light. Near-infrared light travels deeper into caves than visible light because the limestone walls reflect it efficiently. Measurements in the darkest parts of the cave showed near-infrared light levels 695 times higher than at the entrance. The cyanobacteria were densest in these deepest areas, showing they can generate energy in total darkness.
Implications for Extraterrestrial Life
Researchers explored other remote caves in the park and found the same phenomenon. “We showed that not only do they live down there, but they photosynthesize in a completely sheltered environment where they’ve probably been untouched for 49 million years,” Behrendt said. This discovery suggests that life could exist in places previously thought impossible, even beyond Earth.
