Life on Venus? MIT's 'very surprising' discovery of amino acid stability

The results indicate cloudiness Venus It can be hospitable to some forms of life.

If there is life in the solar system outside Earth, it could exist in the clouds of Venus. In contrast to the planet's inhospitable surface, Venus' cloud layer, which extends 30 to 40 miles above the surface, hosts more moderate temperatures that could support some extreme forms of life.

If there were, scientists hypothesized that any inhabitants of the pink cloud would look very different from life forms on Earth. This is because the clouds themselves are made of highly toxic droplets of sulfuric acid sour – A highly corrosive chemical that is known to dissolve metals and destroy most biological molecules on Earth.

But a new study conducted Massachusetts Institute of Technology Researchers may challenge this assumption. Published on March 18 in the magazine AstrobiologyThe study suggests that, in fact, some elements essential for life can survive in concentrated sulfuric acid solutions.

The study authors found that 19 Amino acids Which are essential for life on Earth and are stable for up to four weeks when placed in vials containing 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 sulfuric acid solutions with concentrations ranging from 81 to 98 percent.

“What is quite surprising is that concentrated sulfuric acid is not a universally hostile solvent for organic chemistry,” says study co-author Janusz Petkowski, an affiliated researcher in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

“We have found that the essential elements for life on Earth are stable in sulfuric acid, and this is very interesting to the idea of ​​the possibility of life on Venus,” adds study author Sarah Seager, MIT's 1941 Professor of Planetary Science. He is a professor in the departments of physics and aeronautics and astronautics. “This doesn't mean that life there would be the same as here. In fact, we know it couldn't be. But this work reinforces the idea that Venus's clouds could support the complex chemicals needed for life.”

The study's co-authors include first author Maxwell Seager, an undergraduate student in the Department of Chemistry at Worcester Polytechnic Institute and Seager's son, and William Baines, a research affiliate at MIT and a scientist at Cardiff University.

The building blocks of acid

The search for life in Venus's clouds has gained momentum in recent years, driven in part by the controversial discovery of phosphine — a molecule considered one of the signs of life — in the planet's atmosphere. While this discovery is still under discussion, the news has reinvigorated an old question: Could Earth's sister planet actually host life?

In search of an answer, scientists are planning several missions to Venus, including the first privately funded mission to the planet, with support from California-based launch company Rocket Lab. The mission, for which Seager is the principal scientific investigator, aims to send a spacecraft through the planet's clouds to analyze its chemistry for signs of organic molecules.

Before the mission's launch in January 2025, Seager and her colleagues tested different molecules in concentrated sulfuric acid to see what parts of life on Earth might also be stable in Venus' clouds, which are estimated to be more acidic than orders of magnitude. The most acidic place on Earth.

“People think that concentrated sulfuric acid is a very strong solvent that will cut everything into pieces,” Petkowski says. “But we find that this is not necessarily true.”

In fact, the team has previously shown that complex organic molecules such as some fatty acids and nucleic acids remain surprisingly stable in sulfuric acid. The scientists are keen to stress, as they do in their current paper, that “complex organic chemistry is not life, of course, but there is no life without it.”

In other words, if certain molecules can survive in sulfuric acid, Venus' highly acidic clouds might be habitable, if not necessarily inhabited.

In their new study, the team turned their focus to amino acids, which are molecules that combine to form basic proteins, each with its own specific function. Every living organism on Earth needs amino acids to make proteins, which in turn perform life-sustaining functions, from breaking down food to generating energy, building muscle, and repairing tissue.

“If you look at the four building blocks of life as DNA bases, amino acids, fatty acids, and carbohydrates, we have proven that some fatty acids can form micelles and vesicles in sulfuric acid, and DNA bases are stable in sulfuric acid. It has been shown that carbohydrates are very acidic. Reaction with sulfuric acid
Seager explains. “This leaves us with only amino acids as the final building block
Stady.”

Stable spine

Scientists began their studies on sulfuric acid during the epidemic, and conducted their experiments in a home laboratory. Since that time, Seager and her son have continued to work on the chemistry of concentrated sulfuric acid. In early 2023, they requested samples of a powder of 20 “vital” amino acids—those amino acids essential 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, which represents the range found in the clouds of Venus.

The team then left the flasks incubated for a day before transporting them to MIT's Department of Chemistry Instruments (DCIF), a shared laboratory that operates 24/7 and offers a number of automated and manual instruments for use by MIT scientists. For their part, Seager and her team used the lab's 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 found, to their surprise, that the basic molecular structure, or “backbone,” in 19 of the 20 amino acids remained stable and unchanged, even in highly acidic conditions.

“Just showing that this backbone is stable in sulfuric acid does not mean that there is life on Venus,” says Maxwell Seager. “But if we showed that this spine was compromised, there would be no chance of life as we know it.”

“Now, with the discovery that many amino acids and nucleic acids are stable in 98 percent sulfuric acid, the possibility of life surviving in sulfuric acid may not be so far-fetched or fantastic,” says Sanjay Limaye, a planetary scientist at the university. from Wisconsin, who has studied Venus for more than 45 years, was not involved in this study. “Of course, there are many hurdles ahead, but life that evolved in water and adapted to sulfuric acid may not be so easily ruled out.”

The team acknowledges that Venus's cloud chemistry is likely more chaotic than the study's “test tube” conditions. For example, scientists have measured various trace gases, as well as sulfuric acid, in the planet's clouds. As such, the team plans to incorporate some trace gases into future experiments.

“There are only a few groups in the world now working on the chemistry of sulfuric acid, and they would all agree that no one has the intuition,” Sarah Seager adds. “I think we are happier than anything else because this latest result adds another ‘yes’ to the possibility of life on Venus.”

Reference: “Stability of 20 Vital Amino Acids in Concentrated Sulfuric Acid: Implications for the Habitability of Venus” by Maxwell D. Seager, Sarah Seager, William Baines, and Janusz J. Petkowski, March 18, 2024, Astrobiology.
doi: 10.1089/ast.2023.0082