Photosynthesis maintains Earth's habitability for life as we know it, and shapes the way we search for habitable worlds around distant stars. Scientists have discovered a microbe that can use low-energy light to perform photosynthesis. This discovery could alter theories about the types of stars that could support Earth-like worlds.
In the process of photosynthesis on Earth, plants convert energy from the sun into chemical energy in the form of glucose, or sugar. The chlorophyll in plants absorbs more blue and red light from sunlight, and less green light. Chlorophyll is green, because it reflects green light more than blue and red light. Credit: NASA Ames
Different types of stars have different temperatures and lifetimes. Cooler red M-class stars live a long time, while hotter blue A-class stars have relatively brief lives. These four pictures are actually four different views of our own star, the sun. Each false-color view highlights atomic emission in different temperature regimes of the upper solar atmosphere. Yellow is 2 million Kelvin, green is 1.5 million K, blue is 1 million K, and red is 60 to 80 thousand K. Image Credit: Stereo Project/NASA
Kiang emphasizes the implications that the findings could have in the search for life on extrasolar planets - and the future of life here on Earth:
1) "Planets orbiting red dwarf stars may not get much visible light, but they'll get a lot of NIR light. So, now we know it would still make sense to look for oxygenic photosynthesis on such planets, and we could look for pigment signatures in the NIR."
2) "A. marina appears to be a late evolution, occupying a light niche that is produced by leftover photons from Chl a organisms. Since it can use more solar radiation than Chl a organisms, might our planet evolve to have Chl d outcompete Chl a?"
3) "Biomimicry of photosynthesis continues to be a quest in the development of renewable energy, but no one has yet developed an artificial system as good as Nature to split water. For renewable energy that depends on sunlight, do the lower energy photons used with Chl d mean that we don't need such strong artificial catalysts for producing hydrogen fuel and biofuels?"
The findings could completely change our understanding of a biological reaction that is essential to the modern biosphere of Earth. They may also open new doors for the future of humankind in areas like renewable energy. But for NASA, the study could also have implications for the future of life on Earth — and beyond — that are truly far out.