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The putative detection of phosphine gas in Venus’ atmosphere raised the fascinating question of whether it could be of biological origin.
Given how inhospitable Venus seems to life as we know it, the question has been all the rage. But scientists have now determined that the hell planet may indeed be habitable after all – high in the clouds, well above the scorching surface.
Specifically, the level of solar irradiation at specific altitudes is comparable to solar irradiation on Earth, which means that airborne photosynthetic microbes could presumably survive at these altitudes. In addition, the thick cloud layer would provide some protection against harmful UV rays, and the acidity of these clouds may be below expectations and within acceptable parameters for life.
“Together,” the researchers wrote in their paper, “these photophysical and chemical considerations support a potential for phototrophy in the clouds of Venus.”
As far as livability goes, Venus seems rather improbable. The conditions on the surface are truly hellish. The planet is completely enveloped in a thick atmosphere composed almost entirely of carbon dioxide which spins 60 times faster than the planet itself, producing insane winds.
The sky is filled with thick clouds of sulfuric acid, and its atmospheric pressure at 0 altitude is almost 100 times that of Earth. If that weren’t enough, it’s extremely hot, with an average surface temperature of 471 degrees Celsius (880 degrees Fahrenheit).
So when astronomers announced that they had detected phosphine gas in the planet’s atmosphere last year, controversy ensued. This is because one of the explanations for its presence could be microorganisms.
Phosphine can be found here on Earth in very limited settings, one of which is anaerobic, or low oxygen, ecosystems. It is found in swamps and muds, where anaerobic microbes thrive; it is found in the intestines and intestinal gas. Somehow, anaerobic microorganisms produce phosphine, and the clouds of Venus are anaerobic.
A biological origin is not the only explanation – a volcanic origin is also possible – but to assess the feasibility of a biological origin in the first place, a proper analysis of the habitability of Venus would certainly not go astray.
So, led by biochemist Rakesh Mogul of California State Polytechnic University, Pomona, a team of scientists set out to conduct one. First, they looked at the level of sunlight that can penetrate the clouds of Venus. We have data from the Russian Venus expedition between 1967 and 1983; none of their probes survived for long on the surface, but they did return the measurements they took of the clouds during their descents.
From these and other historical measurements, the researchers were able to calculate the light levels in the clouds and determined that the irradiances in the middle and lower clouds of Venus are similar to those at the surface of the Earth, where photosynthetic life is abundant.
But light levels alone are insufficient. A study earlier this year found that there is simply not enough water activity in the clouds of Venus to support life as we know it. But that might not be the case if the makeup of Venus’s clouds is not what we think it is. Current estimates place the sulfuric acid concentration at 75 percent for medium clouds and 98 percent for lower clouds.
Mogul and his team revisited the data from Venus and determined that the signatures indicating sulfuric acid could also be caused by neutralized forms of sulfuric acid, such as ammonium bisulfate. If so, there could be a lot more water activity – and a lot less acidity – in the clouds of Venus than previous estimates suggest.
This does not mean that it is. The research aims to establish that this is simply possible – which, in turn, opens avenues for future research, including more detailed analysis of the Venusian atmosphere, to determine habitability.
“Our study provides tangible support for the potential for phototrophy and / or chemotrophy by microorganisms in the clouds of Venus,” Mogul said.
“The acidity and activity levels of the water are potentially within an acceptable range for microbial growth on Earth, while the constant lighting with limited UV suggests that the clouds of Venus may be. hospitable for life. We believe the clouds of Venus would make a great target for habitability or life. detection missions, such as those currently planned for Mars and Europe. “
The research was published in Astrobiology.
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