New Analysis Finds No Signs of Life on Venus After Controversial Claims

No biomarkers indicative of airborne, sulfur-metabolizing life have been discovered in a fresh and detailed investigation of the chemistry of Venus' clouds.

For the time being, that implies the question of observable life in Venus' clouds has been answered. It's likely to stay that way until we acquire new information. The chemistry of Venus's upper atmosphere is far too complicated to be explained by the presence of life as we know it.

After a contentious announcement in 2020 that a team of scientists had discovered phosphine gas in the clouds of Venus, speculation about life in the clouds of Venus at temperate altitudes has ran rampant.

However, the concept is not new; in fact, it was introduced by biophysicist Harold Morowitz and astronomer Carl Sagan almost 50 years ago, in 1967.

More recently, scientists have argued that the chemistry might include hints — and that life in the clouds of Venus may have developed sulfur-based metabolism, similar to what we have observed in microbes here on Earth. Sulfur dioxide (SO2), a sulfur chemical, has an unusual characteristic on Venus: it is plentiful at lower altitudes but relatively low at higher altitudes.

"We've spent the past two years trying to explain the weird sulfur chemistry we see in the clouds of Venus," says University of Cambridge astronomer and chemist Paul Rimmer.

"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." 

Unless it's underground or in a cave or something, life as we know it isn't particularly adept at disguising its existence, no matter how skilled it is at odd chemistry.

Biological processes take components from their surroundings and release them back into it. A good example is respiration: we humans inhale oxygen and exhale carbon dioxide. (Trees take CO2 and release oxygen, which is an excellent system.)

Venus has a vastly different chemistry from Earth, with a sulfur-rich atmosphere that reaches concentrations 100,000 times greater than those found on Earth, tied up in molecules such sulfur dioxide, sulfuric acid, and carbonyl sulfide.

So, in a recent study conducted by astronomer Sean Jordan of the University of Cambridge, a group of researchers looked into the chemical processes we could predict given the energy sources accessible in Venus' atmosphere.

"We looked at the sulfur-based 'food' available in the Venusian atmosphere – it's not anything you or I would want to eat, but it is the main available energy source," Jordan explains.

"If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere."

The peculiar sulfur dioxide signal piqued my curiosity. The chemical is formed by volcanic activity on Earth, and it's probable that it's the same on Venus.

If animals with sulfur-based metabolism lived in Venus's upper atmosphere, they may be to blame for the strange absence of sulfur dioxide at such altitudes.

Scientists have devised sulfur-based metabolisms that may hypothetically use chemical species found in Venus' atmosphere.

Jordan and his colleagues used them as a starting point to simulate the chemical processes that would occur if those lifeforms were present, in order to test if they produced the known composition of the Venusian atmosphere.

Jordan and his colleagues used them as a starting point to simulate the chemical processes that would occur if those lifeforms were present, in order to test if they produced the known composition of the Venusian atmosphere.

They discovered that sulfur-metabolizing life may cause the observed sulfur dioxide depletion; but, the metabolic processes of a biomass of the size necessary would create other molecules in abundances that, in short, aren't there.

"If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus's atmospheric chemistry," Jordan adds.

"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."

That remains an unresolved subject since we don't know how or why sulfur dioxide is sucked out of Venus' upper atmosphere. It's also feasible that a biosphere with an unknown metabolism exists, which we won't know about until a probe arrives to investigate. That's quite thrilling.

Meanwhile, the team claims that their research provides a foundation for simulating the influence of an aerial biosphere on other worlds and, as a result, searching for life in exoplanet atmospheres. This is particularly useful given that exoplanet atmospheres are the ideal area to look for indications of life.

"Even if 'our' Venus is dead, it's possible that Venus-like planets in other systems could host life," Rimmer argues.

"We can take what we've learned here and apply it to exoplanetary systems – this is just the beginning." 
New Analysis Finds No Signs of Life on Venus After Controversial Claims New Analysis Finds No Signs of Life on Venus After Controversial Claims Reviewed by Lilit on June 15, 2022 Rating: 5
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