Dark‑Cave Greens Show Life Can Thrive Without Sunlight

In 2018, two scientists walked deep into a remote part of the Carlsbad Caverns in New Mexico. They found walls covered with a bright green substance that could not have been reached by any visible light. The green coating is made of tiny cyanobacteria that use two uncommon pigments, chlorophyll d and f. These pigments can capture light that is invisible to humans but exists in the near‑infrared spectrum. Inside the cave, rocks act like mirrors and bounce this invisible light around. Measurements revealed that in places far from the entrance, the amount of near‑infrared light was 695 times higher than at the mouth. The largest colonies of bacteria were found exactly in those dark corners. The team then checked other caverns in the same park and found similar bacteria everywhere.This discovery suggests that life can survive and even photosynthesize in environments that are completely cut off from the sun. The implications reach beyond Earth. Most stars in our galaxy are red dwarfs that emit mostly near‑infrared light. If these bacteria can thrive on such light, similar organisms might exist on planets orbiting those stars. The researchers have proposed a NASA study to learn the minimum light levels required for life, information that could help astronomers spot habitable worlds with telescopes like the James Webb. The find also hints that oxygen could be produced on planets without visible light if the right kind of microbes are present. Finding oxygen in an exoplanet’s atmosphere would then become a strong sign of life. The scientists believe the bacteria in the caves have lived untouched for about 49 million years, giving a glimpse into how life can endure in extreme darkness.