2021-11-11

What would photosynthesis look like on a planet?

By yqqlm yqqlm

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we can observe the existence of red edges in the celestial spectrum of the earth. Because plants absorb a lot of red light, but rarely infrared light, the spectral curve of this band will show a “steep slope”. Satellites above the earth will use this feature to track vegetation growth. Astrobiologists may also find this feature on other planets as one of the signs of life

What would photosynthesis look like on a planet?

in a new study recently published in the frontier of astronomy and space science, scientists used a variety of chemical and physical models of photosynthesis to find the best wavelength around different stars and most suitable for plant absorption

life on earth interacts with sunlight through a chemical called chlorophyll a. The substance can capture light and be used for photosynthesis. The light they absorb can be used by plants as energy for biological processes. Biologists believe that the reason why plants rely on chlorophyll a is that it can maximize the energy absorbed from sunlight and minimize the energy required for photosynthesis, so as to maximize the energy output rate of plants

but what if the light from the sun is different in color? Will chlorophyll a still be the most suitable chemical for this task? Probably not, because plants that rely on other stars also need to be adjusted according to the corresponding light to maximize energy efficiency. This means that if we want to look for the red edge effect on the planets around other stars, we may get nothing, because these planets are not necessarily “red” edges, they may be blue edges, they may be red edges of another hue, and they may not even be in the range of visible light

What would photosynthesis look like on a planet?(1)

the figure shows which light plants around different stars absorb the most. Type F stars are the brightest and type M stars are the darkest

the researchers of this new study are composed of scientists from NASA Ames Research Center, NASA Goddard Space Flight Center and the University of Washington. They considered a variety of factors, such as the amount of light at each wavelength in the light of stars, the impact of earth like atmosphere, and the energy consumption of cells for photosynthesis. Their goal is to find out whether future telescopes should search for the “red” edge as a sign of extrasolar life

using a series of chemical and physical equations, they established several models to determine the optimal wavelength of photosynthesis for plants around different types of stars. Then, the results of these models are compared with the earth’s vegetation, and the absorption spectra of spinach and other plants are reconstructed. By applying these models to well-known plants such as spinach, they can test whether their calculations are correct. It is found that around stars brighter and hotter than the sun (such as type F stars with a temperature half higher than the sun), plants tend to absorb higher energy light to produce a “blue edge”; while around stars with a temperature lower than the sun (such as type K and M stars) , plants mainly absorb light with lower energy, and the edge color is redder or even close to infrared light.

interestingly, except for the stars with the lowest temperature (the temperature is only half or even lower than that of the sun) , all the edges generated by these models are in the visible light range. Although the spectral range is large, the light most suitable for plants to generate energy is still concentrated in a small visible light band. The researchers also found in the model that the growth of plants is not limited by the amount of energy around any kind of star, but is more affected by factors such as land and nutrients

these models have been improved on the basis of previous studies. Scientists previously believed that the light emitted by stars can be established as a simple curve model by using the detailed spectra of different types of stars. In addition, they have been inferring on the basis of the earth’s atmosphere before, but the atmospheric composition of exoplanets may be different from that of the earth. Because the atmosphere will absorb light Part of the light emitted by stars and the atmosphere will also affect the light absorbed by plants on the planet’s surface.

although there are more and more complex factors that can be added to these models, such as different atmospheric components and different leaf shapes, this study has laid a good foundation for searching alien plants. In the next few decades, we will use habex and luvoir This information may really help scientists find extraterrestrial vegetation. These two space telescopes should be able to provide us with atmospheric spectral information of earth like planets, and may even find the red edge (or blue edge) effect on extrasolar planets. (leaves)