The unusual behavior of sulfur in the atmosphere of Venus can not be explained by the “air” form of extraterrestrial life, according to a new study.
Scientists at Cambridge University used a combination of biochemistry and atmospheric chemistry to test the “life in the clouds” hypothesis, which astronomers have been pondering for decades, and found that life could not explain the composition of Venus’s atmosphere. Any form of life in sufficient quantity must leave chemical imprints in the planet’s atmosphere, as it consumes food and throws away waste. However, Cambridge researchers have not found any signs of such imprints on Venus.
The researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur given the known sources of chemical energy in Venus’ atmosphere. The models considered one feature of the Venusian atmosphere – a large amount of sulfur dioxide (SO2). On Earth, most SO2 in the atmosphere is formed as a result of volcanic emissions. On Venus, high levels of SO2 are observed lower in the clouds, but are somehow “sucked out” of the atmosphere at high altitudes.
Researchers have launched a model of metabolic responses to test whether they can explain the decrease in SO2 levels. They found that metabolic reactions can reduce SO2 levels, but only by producing other molecules in very large quantities that are not visible. The results set a hard limit on how much life can exist on Venus without destroying our understanding of how chemical reactions take place in planetary atmospheres – it turned out that this is not a viable solution.
There is no evidence that the clouds of Venus hide life that feeds on sulfur, but researchers say that studying the chemical behavior of our neighbor may help scientists find out how similar planets behave throughout the galaxy. “Even if our Venus is dead, it is possible that there may be life in other systems on Venus-like planets,” the scientists conclude.