Life might survive the sulfuric acid clouds of Venus, new experiments find

Venus may be a hellscape by our standards, but there’s a chance that some forms of life could evolve there. A new MIT study has now found that the building blocks of life are surprisingly stable in highly concentrated sulfuric acid – which Venus’ clouds happen to be made of.

Thick cloud cover gave early science fiction writers free reign to imagine the surface of Venus as a paradise, but as technology improved science fact once again ruined the party. It’s a dry, hot, pressure-cooker of a planet, with surface temperatures of up to 464 °C (867 °F) – hot enough to melt lead – and air pressure equivalent to being 900 m (3,000 ft) beneath the sea. Throw in clouds of sulfuric acid and a suffocating atmosphere of 96% carbon dioxide, and Venusian real estate is starting to look pretty cheap.

While many alien hopefuls might cast their eye towards Mars, or moons like Europa, Enceladus and Titan, Venus has clawed its way back into the headlines in recent years. Conditions are thought to be more hospitable at altitudes between about 48 and 60 km (30 and 37 miles) above the surface, where the temperature and pressure drops and there’s more water around. Intriguingly, that’s about the altitude where strange dark patches have been spotted drifting through the Venusian clouds, with optical signatures suspiciously similar to a bacteria species here on Earth.

But there’s a major problem that life might face in that airborne oasis – sulfuric acid clouds. Previous studies have suggested that they could be shielded by other particles in the air up there, but a new study has found that microbes might not even need protection, and could be just fine floating around in sulfuric acid.

An MIT team placed all 20 'biogenic' amino acids – chemicals that are essential to all life as we know it – into vials of sulfuric acid at concentrations of 81-98%, levels they’d face in Venusian clouds. Surprisingly, 19 of them were found to remain stable even at the highest concentrations, with their molecular 'backbones' remaining intact. This lasted for the entire four weeks of the study, with the team ending things there because there was no further signs of activity.

“We are finding that building blocks of life on Earth are stable in sulfuric acid, and this is very intriguing for the idea of the possibility of life on Venus,” said Sara Seager, an author of the study. “It doesn’t mean that life there will be the same as here. In fact, we know it can’t be. But this work advances the notion that Venus’ clouds could support complex chemicals needed for life.”

Amino acids aren’t the only life ingredients that have proven hardy in sulfuric acid: The team has previously shown that some fatty acids and nucleic acids show similar stability. The scientists do make a very careful distinction to keep in mind though: “complex organic chemistry is of course not life, but there is no life without it.” It basically means the ingredients of life can survive there, but it remains to be seen whether they actually are present, let alone whether evolution has cobbled them together into lifeforms. The researchers also acknowledge that the actual chemistry of Venus' atmosphere is of course far more complex than their lab recreation.

This study lends a little weight to the “yes” side of the ongoing debate about life on Venus, but unfortunately it still seems like the “no” side is currently winning. One of the most exciting finds in recent years came in 2020 with the announcement that astronomers had detected phosphine in the Venusian atmosphere, a rare chemical that here on Earth is mostly produced by anaerobic microbes. However, a later study found that the signature was most likely common sulfur dioxide. Others found that Venus has too little water for life, and is missing other biosignatures that would be expected.

Either way, we may know for sure sooner rather than later. The upcoming Venus Life Finder mission involves sending a spacecraft to skim those acidic clouds for signs of life, and is planned for launch at the end of 2024.

The research was published in the journal Astrobiology.

Source: MIT