The building blocks of life are stable in Venus' atmosphere

An MIT study discovered the stability of amino acids in sulfuric acid. The clouds of Venus may be suitable for some life forms.

03/20/2024, Jennifer Chu, MIT News

If there is life in the solar system beyond Earth, it can be found in the clouds of Venus. Unlike that planet's inhospitable surface, Venus's cloud layer, 30 to 40 miles above the surface, has more moderate temperatures where some extreme life forms can survive.

Scientists suggest that any inhabitants of the Venusian clouds, if they exist there, are very different from life forms on Earth. This is because the clouds themselves are made up of droplets of highly toxic sulfuric acid, a highly caustic chemical that is known to dissolve metals and destroy most biological molecules on Earth.

But a new study by scientists at the Massachusetts Institute of Technology may challenge this assumption. A study published in the journal Astrobiology reports that some key building blocks of life may, in fact, be preserved in concentrated sulfuric acid solutions.

The study authors found that 19 amino acids that are essential for life on Earth are stable for up to four weeks when placed in vials of sulfuric acid at concentrations similar to those found in the clouds of Venus. In particular, they found that the molecular backbone of all 19 amino acids remained intact in solutions of sulfuric acid with concentrations ranging from 81 to 98 percent.

“What is absolutely surprising is that concentrated sulfuric acid is not a solvent, which is universally hostile to organic chemistry,” says study co-author Janusz Petkowski, a postdoctoral fellow in MIT's Department of Earth, Atmospheric and Planetary Sciences. and Planetary Sciences – EAPS).

“We found that the building blocks of life on Earth are stable in sulfuric acid, which is very exciting for the idea of ​​life on Venus,” adds study author Sarah Seeger, professor of planetary sciences in MIT's EAPS Department and professor in the departments of physics and aeronautics. and astronautics. – This does not mean that life there will be the same as here. In fact, we know that this cannot be true. But this work raises the idea that Venus's clouds may contain complex chemicals necessary for life.”

Co-authors of the study include first author Maxwell Seeger, a chemistry student at Worcester Polytechnic Institute (son of Sarah Seeger), and William Baines, a research fellow at MIT and a scientist at Cardiff University.

Building blocks in acid

The search for life in the clouds of Venus has gained momentum in recent years thanks to the controversial discovery of phosphine, a molecule believed to be one of the hallmarks of life, in the planet's atmosphere. While the discovery remains a matter of debate, the news from MIT has reignited an old question: Could a planet related to Earth really support life?

In search of an answer, scientists are planning several missions to Venus, including the first mission to the planet, largely privately funded, backed by California-based Rocket Lab. The mission, for which Seager is the principal investigator, aims to send a spacecraft through the planet's clouds to analyze their chemical composition for signs of organic molecules.

Ahead of the mission's planned January 2025 launch, Seeger and her colleagues tested different molecules in concentrated sulfuric acid to see which fragments of Earth's life might also be stable in the clouds of Venus, which are estimated to be several orders of magnitude more acidic. than the most acidic places on Earth.

“People have this idea that concentrated sulfuric acid is an extremely aggressive solvent that will cut everything to pieces,” Petkowski says. “But we believe that this is not necessarily the case.”

In fact, the team previously showed that complex organic molecules, such as some fatty acids and nucleic acids, remain surprisingly stable in sulfuric acid. In their scientific article, the scientists try to emphasize that “complex organic chemistry, of course, is not life, but without it there is no life.”

In other words, if certain molecules can be preserved in sulfuric acid, then perhaps the highly acidic clouds of Venus are habitable, although not necessarily habitable.

In their new study, the team focused on amino acids – molecules that combine to form essential proteins, each with a specific function. Every living thing on Earth requires amino acids to produce proteins, which in turn perform life-sustaining functions, from breaking down food to generating energy, building muscle mass, and repairing tissue.

“If you consider the four basic building blocks of life, which are nucleic acid bases, amino acids, fatty acids and carbohydrates, we have demonstrated that some fatty acids can form micelles and vesicles in sulfuric acid, and nucleic acid bases are stable in sulfuric acid. Carbohydrates have been shown to be highly reactive to sulfuric acid, explains Maxwell Seeger. “This left us with only amino acids as the last basic building block to study.”

Stable frame

Scientists began researching sulfuric acid during the pandemic, conducting experiments in a home laboratory. From this time on, Seeger and her son continued work on the chemistry of concentrated sulfuric acid. In early 2023, they ordered samples of a powder of 20 “biogenic” amino acids – those amino acids that are necessary for all life on Earth. They dissolved each type of amino acid in vials of sulfuric acid mixed with water at concentrations of 81 and 98 percent, similar to the range found in the clouds of Venus.

The team then left the vials to incubate for a day before transporting them to the MIT Department of Chemistry Instrumentation Facility (DCIF), a shared 24-hour laboratory that offers MIT scientists a range of automated and manual instruments. Seager and her team also used a laboratory nuclear magnetic resonance (NMR) spectrometer to analyze the structure of amino acids in sulfuric acid.

After analyzing each vial several times over four weeks, the scientists were surprised to find that the basic molecular structure, or “backbone,” of 19 of the 20 amino acids remained stable and unchanged even under highly acidic conditions.

“Simply demonstrating that this core is stable in sulfuric acid does not mean that there is life on Venus,” notes Maxwell Seager. “But if we showed that this framework was compromised, then life as we know it would have no chance.”

The team acknowledges that the chemistry of Venus's clouds is likely more confusing than the test-tube conditions. For example, scientists measured various gas impurities in the clouds of the planet, in addition to sulfuric acid. So the team plans to include some trace gases in future experiments.

“There are only a few groups in the world right now working on sulfuric acid chemistry, and they would all agree that no one has a clue,” adds Sarah Seeger. “I think what we're most excited about is that this latest result adds another 'yes' to the possibility of life on Venus.”

Translation: Alexander Tarlakovsky (blog tay-ceti.space)
Original: Study: Life's building blocks are surprisingly stable in Venus-like conditions

Research Article: Stability of 20 biogenic amino acids in concentrated sulfuric acid: implications for cloud habitability of Venus.