Dark‑Cave Greens Show Life Can Thrive Without Sunlight
In 2018, two scientists ventured deep into a remote section of Carlsbad Caverns in New Mexico and uncovered an astonishing discovery: walls coated with a bright green substance that could not have been illuminated by any visible light.
What Makes It Green?
The coating is composed of tiny cyanobacteria that utilize two rare pigments—chlorophyll d and chlorophyll f. These pigments allow the bacteria to capture light that is invisible to humans but exists in the near‑infrared spectrum.
How Light Bounces Inside
- Rocks as mirrors: The cave’s rocky surfaces reflect and bounce the invisible light around.
- Surge in infrared: Measurements revealed that in areas far from the entrance, near‑infrared light levels were 695 times higher than at the mouth.
- Optimal habitats: The largest colonies of bacteria were found precisely in those dark corners.
A Widespread Phenomenon
The team extended their search to other caverns within the same park and detected similar bacteria everywhere, indicating that this is not an isolated case.
Implications for Life Beyond Earth
- Red dwarfs and near‑infrared light: Most stars in our galaxy are red dwarfs, emitting predominantly near‑infrared radiation.
- Potential exoplanetary life: If these bacteria can thrive on such light, similar organisms might exist on planets orbiting red dwarfs.
- NASA’s next step: Researchers propose a NASA study to determine the minimum light levels required for life—information that could help astronomers identify habitable worlds with telescopes like the James Webb Space Telescope.
- Oxygen production: The discovery hints that oxygen could be generated on planets lacking visible light, provided the right microbes are present. Detecting oxygen in an exoplanet’s atmosphere would then become a strong biosignature.
A Glimpse into the Past
Scientists estimate that these cave bacteria have lived untouched for about 49 million years, offering a window into how life can endure in extreme darkness.
Takeaway
The Carlsbad Caverns discovery expands our understanding of photosynthesis, demonstrating that life can not only survive but also thrive in environments completely cut off from the sun—paving the way for new searches for life across the cosmos.
