Вадим Дудченко
Администратор портала

Possible lifeforms in the Venusian clouds could be setting off a cascade of chemical reactions that is making the environment much more habitable, according to a paper published in the Proceedings of the National Academy of Sciences.

An artist’s conception of the aerial biosphere in the cloud layers of Venus. In this picture, hypothetical microbial life in the clouds of Venus resides inside protective cloud particles and is carried by winds around the planet. Image credit: J. Petkowska.

Venus is often called Earth’s sister planet because of its similar mass and size to Earth. Yet, owing, in part, to the greenhouse effect from its massive atmosphere dominated by carbon dioxide, Venusian surface temperature is higher than 700 K (427 degrees Celsius, 800 degrees Fahrenheit) — too hot for life of any kind.

The surface of Venus is therefore a complete contrast to Earth’s temperate surface and rich surface biosphere.

Venus is perpetually shrouded in a 20-km- (12.4-mile) deep layer of clouds, including the temperate atmosphere layers at 48 km to 60 km (30-37.2 miles).

The prevailing consensus is that these clouds are made from droplets of concentrated sulfuric acid.

While the clouds are often described as ‘temperate’ or ‘clement,’ such a statement is misleading when it comes to habitability. If the cloud particles are actually made of concentrated sulfuric acid, then it is difficult to imagine how life chemically similar to life on Earth could survive.

In the 1970s, Venera 8 and Pioneer Venus probes tentatively detected ammonia (NH3) in the planet’s clouds.

“Ammonia shouldn’t be on Venus,” said Professor Sara Seager, a researcher in the Department of Earth, Atmospheric and Planetary Sciences at MIT.

“It has hydrogen attached to it, and there’s very little hydrogen around. Any gas that doesn’t belong in the context of its environment is automatically suspicious for being made by life.”

In the new study, Professor Seager and colleagues modeled a series of chemical processes in search of an answer.

They found that if life were producing ammonia in the most efficient way possible, the associated chemical reactions would naturally yield oxygen.

Once present in the clouds, ammonia would dissolve in droplets of sulfuric acid, effectively neutralizing the acid to make the droplets relatively habitable.

The introduction of ammonia into the droplets would transform their formerly round, liquid shape into more of a nonspherical, salt-like slurry.

Once ammonia dissolved in sulfuric acid, the reaction would trigger any surrounding sulfur dioxide to dissolve as well.

The presence of ammonia then could indeed explain most of the major anomalies seen in Venus’ clouds.

The researchers also show that sources such as lightning, volcanic eruptions, and even a meteorite strike could not chemically produce the amount of ammonia required to explain the anomalies. Life, however, might.

In fact, there are lifeforms on Earth — particuarly in our own stomachs — that produce ammonia to neutralize and make livable an otherwise highly acidic environment.

“There are very acidic environments on Earth where life does live, but it’s nothing like the environment on Venus — unless life is neutralizing some of those droplets,” Professor Seager said.

“There are many other challenges for life to overcome if it is to live in the clouds of Venus,” said Dr. William Bains, a researcher in the School of Physics and Astronomy at Cardiff University.

“There is almost no water there for a start, and all life that we know of needs water. But if life is there, then neutralizing the acid will make the clouds just a bit more habitable than we thought.”

The scientists may have a chance to check for the presence of ammonia, and signs of life, in the next several years with the Venus Life Finder Missions that plan to send spacecraft to Venus to measure its clouds for ammonia and other signatures of life.

“Venus has lingering, unexplained atmospheric anomalies that are incredible. It leaves room for the possibility of life,” Professor Seager said.

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William Bains et al. 2021. Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies. PNAS 118 (52): e2110889118; doi: 10.1073/pnas.2110889118

 



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