New research has shown that life as we know it is impossible in the atmosphere of Venus. The results are published by Nature Astronomy.
The search for life on the planet closest to Earth has so far proven fruitless. In 2020, scientists discovered phosphine gas in the atmosphere of Venus, which is known to be produced by bacteria on Earth. Later, this discovery was questioned, it turned out that scientists took a completely different substance for phosphine – sulfur dioxide.
In a new study, scientists wondered if there is enough water in Venus’s atmosphere to make life possible on the planet. It turned out that, despite the moderate temperature in the middle layers of the atmosphere of Venus, there is no other necessary condition for life. Namely, a sufficient amount of water, most of which is contained in drops of sulfuric acid.
To understand if life is possible in the planet’s atmosphere, scientists evaluated water activity – a parameter associated with relative humidity. Water activity determines the efficiency of microbial cells, therefore it determines habitability. This parameter ranges from 0 to 1, with the unit corresponding to 100% humidity.
In 2017, microbiologist John Hallsworth discovered a terrestrial fungus that can survive at a humidity setting of 0.585. These are the driest conditions under which biological activity has ever been measured. However, even such persistent organisms cannot survive in the atmosphere of Venus. It turned out that the water activity there is no more than 0.004. In other words, the atmosphere on the planet turned out to be a hundred times drier than the limit of the existence of the most hardy organisms on Earth.
To calculate the concentration of water, scientists used existing measurements from seven American and Soviet probes and one orbiter sent to Venus in the late 1970s and early 1980s.