Strange Sulfur at Venus not a Sign of Life

Jun 16, 2022 | Daily Space, Venus

IMAGE: The northern (left) and southern hemispheres of Venus. Created using radar, the images give us a view of how the surface may look below the planet’s thick atmosphere. CREDIT: Pixabay

With NASA and the European Space Agency (ESA) gearing up to explore Venus in more detail, scientists continue to explain strange discoveries in the Venusian atmosphere. This time, a team of researchers tested the hypothesis that some unusual type of cloud-based life was causing elevated levels of sulfur dioxide. Their findings, published in Nature Communications, basically answer… no. We’re not looking at a biological process.

Of course, all the hullabaloo over phosphine in the atmosphere and the Jurassic Park quoting of “life finds a way” keeps researchers excited to examine all the possibilities. Co-author Paul Rimmer notes: Life is pretty good at weird chemistry, so we’ve been studying whether there’s a way to make life a potential explanation for what we see.

To explore this particular hypothesis, the team combined atmospheric and biochemical models and studied the various chemical reactions. If sulfur is being used as a food source from some exotic form of life, they thought, then there should be evidence in the chemical composition of the atmosphere. Nutrients taken in mean energy produced and waste products expelled, after all.

First, we have to compare Venus to Earth. On Earth, our atmospheric sulfur dioxide is the result of volcanic activity. Venus has volcanoes, possibly even active ones, that could be supplying the atmosphere with sulfur dioxide on an ongoing basis. That sounds reasonable enough. But then, at higher levels in the atmosphere, the sulfur dioxide disappears. So perhaps drops in sulfur dioxide were due to consumption.

Next, the team added metabolic reactions to the model that would result from life possibly consuming sulfur dioxide and producing those waste products. And then they checked the data from Venus’s atmosphere to see if those particular molecules were present.

It turns out that yes, the metabolic reactions could produce the drop in sulfur dioxide seen; however, the by-products released just aren’t present in the quantities necessary to indicate life. First author Sean Jordan explains: If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry. We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved—there’s lots of strange chemistry to follow up on.

And some of that follow-up could be done with JWST because our newest telescope (well, almost) is really sensitive to these types of sulfur molecules. Life or not, Venus is incredibly fascinating.

More Information

University of Cambridge press release

Proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus,” Sean Jordan, Oliver Shorttle, and Paul B. Rimmer, 2022 June 14, Nature Communications

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