It seemed such a beautiful and appropriate hypothesis: aliens living high in the atmosphere of Venus and secretly sniffing sulfur dioxide. But the exciting hypothesis can go in the trash.

Using models, researchers show that, in theory, aliens may be able to nibble on the sulfur dioxide high in Venus’ atmosphere, but in practice it results in the formation of other molecules. And they would be produced in such quantities that we can detect them quite easily. But – and now it comes – we don’t see those molecules at all. “We wanted life to be a possible explanation, but when we checked the models, it turned out not to be a sustainable solution,” said researcher Sean Jordan.

The problem

The problem Jordan and colleagues were looking for a solution to is found in the atmosphere of Venus. There is something strange going on. A little deeper in that atmosphere we find quite high concentrations of sulfur dioxide, but at higher altitudes the sulfur dioxide is much more scarce. As if the sulfur dioxide is being sucked out of the air there.

wild speculation

Rather, it sparked wild speculation. Because why did the sulfur dioxide ‘disappear’ high in the atmosphere? Were there aliens behind that? “If life is present, it must affect the chemical composition of the atmosphere,” said researcher Oliver Shorttle. “Could life be the reason that the concentration of sulfur dioxide on Venus (higher in the atmosphere, ed.) is declining so much?”

Living in the clouds

Some researchers thought so. They imagined extraterrestrial life that existed high in the atmosphere of Venus and ‘snacked’ sulfur dioxide there. “It’s not something you can or want to eat,” Jordan emphasizes. “But it is the most important source of energy available.”

Models

Jordan and colleagues decided to take a closer look at the idea that aliens are harnessing the sulfur dioxide high in Venus’ atmosphere. To this end, Jordan developed models that describe, among other things, which metabolic processes must take place in these extraterrestrial beings when they ‘use’ sulfur dioxide and which waste products are created. They then used those models to determine whether aliens and the metabolic processes that take place in them could be responsible for the decline in sulfur dioxide we see high in Venus’ atmosphere.

Nope..

And at first it looked promising. For example, the models show that the metabolic reactions could lead to a decrease in atmospheric sulfur dioxide. But – so the researchers had to quickly conclude – these metabolic reactions produce large amounts of other molecules that we do not see in the same atmosphere. “If life were responsible for the sulfur dioxide concentrations we see on Venus, it would contradict everything we know about the composition of Venus’ atmosphere,” Jordan said.

Issue

So no sulphur-eating aliens in the atmosphere of Venus. It may be a bit disappointing, but for the researchers it mainly means that there is still a lot of work to be done. “Because if life isn’t responsible for what we see on Venus, then we still have a problem to solve,” Jordan notes.

And so the atmosphere of Venus remains somewhat mysterious. It is almost certain that even more atmospheric mysteries will come to scientists in due course. In a few weeks, the James Webb Space Telescope will open its eyes and start sifting through the atmospheres of planets outside our solar system. And there, too, we will undoubtedly encounter surprises. Findings about the atmospheres of planets closer to home—such as Venus—could be very helpful in interpreting what we see in those exoplanetary atmospheres. “Even if ‘our’ Venus does not harbor life, it is possible that Venus-like planets in other systems do harbor life,” notes researcher Paul Rimmer. “We can also apply what we have learned to exoplanetary systems – this is just the beginning.”