Certain minerals may be the source of photosynthesis!

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Recently, Chinese scientists have developed a new theory about photosynthesis. Certain inorganic minerals lining the earth’s surface would be able to absorb the energy of sunlight before channeling the latter in chemical reactions.

Minerals capable of photosynthesis

As a reminder, photosynthesis is a bioenergetic process giving the ability to certain organisms to synthesize organic matter using sunlight. When we talk about this phenomenon, it is more precisely a question of oxygenic photosynthesis. The latter made its appearance in cyanobacteria (or “blue algae”) 2.45 billion years ago. This is the main route for transforming mineral carbon into organic carbon.

This ability of cyanobacteria generated a real ecological upheaval on earth. While its atmosphere was rich in methane, it underwent a transformation to give the current atmosphere, essentially composed of nitrogen (78.08%) and dioxygen (20.95%). Without cyanobacteria, life might not have never made an appearance on our planet.

Cyanobacteria under the microscope.
Credits: NASA / Wikipedia

According to a study published by a team from Peking University (China) on December 23, 2020, minerals were already capable of photosynthesis before cyanobacteria. Scientists initially attempted to answer the following question: How did the first bacteria evolve in order to become capable of photosynthesis?

At the origin of the transformation of the primitive Earth

Scientists have mentioned the terms “birnessite”, “goethite” or even “hematite”. It is inorganic minerals present on the surface of the Earth. These would also be able to absorb the energy of sunlight before proceeding with chemical reactions. These minerals are semiconductors and therefore sensitive to a specific wavelength of light. When these absorb photons, part of their electrons get excited. These “jump” towards higher energy states, occasionally generating reduction reactions. However, these effects usually need an external source of energy to exist.

Thus, the study speaks of a new mechanism that can catalyze reactions similar to that of oxygenic photosynthesis. Certain minerals would then be capable of facilitating the fixation of carbon or the division of water molecules into hydrogen and oxygen atoms. It may also be to promote the conversion of CO2 into carbonates.

In their conclusion, the study’s leaders claim that these mechanisms potentially transformed the early Earth. Significant changes then appeared in atmospheric (and marine) conditions. However, this would have had the effect of promote the evolution of the first forms of life, including cyanobacteria. Finally, this work could one day make it possible to manufacture more efficient solar panels or to develop new techniques in water treatment.





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