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No signs of life in the atmosphere of Venus

No signs of life in the atmosphere of Venus
Written by insideindyhomes

Compared to Earth, Venus is a hostile planet – with about 100 times the pressure and a temperature of around 450 degrees Celsius on the planet’s surface. But in the dense atmosphere of Venus, at an altitude of 50 to 60 kilometers, the temperature and pressure are similar to those at the Earth’s surface. For a long time, astrobiologists have therefore speculated that bacterial life could at least exist there. However, a research team has now had to reject this hypothesis. The metabolism of such microbes would not be consistent with the observed composition of the Venusian atmosphere, the scientists say in the journal Nature Communications.

“We spent two years trying to explain the strange sulphur-based chemistry in the clouds of Venus,” explains Paul Rimmer of the University of Cambridge. In particular, the abundance of sulfur dioxide in the atmosphere of Venus is puzzling. On Earth, sulfur dioxide comes primarily from volcanoes. There are also active volcanoes on Venus that could spew sulfur dioxide into the atmosphere. However, the proportion of this gas is only high in the lower cloud layer – above that it decreases again rapidly. According to Rimmer and his colleagues, some process there has to consume the sulfur dioxide.

“Life is pretty good at creating weird chemistry. That’s why we looked for ways to explain the observations with the help of bacteria,” explains Rimmer. The researchers’ idea: The sulfur dioxide serves as food and energy source for bacteria in the temperate region of the atmosphere. So the scientists made a list of possible metabolic reactions based on sulfur dioxide to see if that could explain the reduction in the gas. And they were initially successful with this: bacteria could actually reduce the proportion of sulfur dioxide, so that it decreases with increasing altitude.

But the supposed success has a catch: Such a metabolism always produces excretions – other molecules that are not present in the Venusian atmosphere. The researchers therefore had to reject their hypothesis. “Our models show that it doesn’t work,” says Rimmer’s colleague Sean Jordan. “They go against everything we know about the atmosphere of Venus.”

The mystery of sulfur dioxide in Venus’ atmosphere thus remains unsolved. The researchers now want to explore non-biological approaches to the strange chemistry in the planet’s clouds. They also hope to soon be able to apply their method to planets around other stars. With the new James Webb space telescope, for example, sulfur compounds could be detected there. “We can then also apply what we learned from Venus to exoplanets,” says Rimmer.

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