New research is focusing on the sulfuric-acid clouds of Venus as a potential abode for life.
The new Venus study calls for the start of a new branch of astrobiology and a new branch of organic chemistry.
"The search for signs of life beyond Earth is a motivator in modern-day planetary exploration, but life on other planets does not have to have the same biochemistry as our life here on Earth," said Janusz Pętkowski, a research affiliate at the Massachusetts Institute of Technology (MIT) in Cambridge. "Life needs some sort of liquid medium to function, but does it always have to be water?"
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Amino acids are surprisingly stable
A major finding of the new study, which appears in a special collection of "Venues" research papers in the journal Astrobiology, is that amino acids remain stable in concentrated sulfuric acid. That's extremely interesting to astrobiologists, for amino acids are the building blocks of proteins, which are essential for life as we know it.
And that brings us full circle to those sulfuric acid-laden Venusian clouds. Venus is often called Earth's sister planet, but is it also a celestial companion of cozy microbes?
"These findings significantly broaden the range of biologically relevant molecules that could be components of a biochemistry based on a concentrated sulfuric acid solvent," Pętkowski and his research colleagues state in the paper, which is titled "Stability of 20 Biogenic Amino Acids in Concentrated Sulfuric Acid: Implications for the Habitability of Venus' Clouds."
Solvent for life
Pętkowski points to other potential liquid solvents on the surface, subsurface or in the clouds of planets and moons. "Therefore, it is important to understand the basic chemistry that happens in such potential alternative solvents for life, to assess if complex organic chemistry could form in them, be stable and soluble. On Earth, water is a dominant liquid, but other liquid solvents are also present in our solar system," he told Space.com.
Pętkowski is interested in research related to hunting for life on exoplanets, biosignature gases and theoretical biochemistry. One goal of his work is determining whether or not any universal laws of biology can be identified, a pursuit that uses "cheminformatics" computer simulations as an aid in designing future laboratory experiments.
The research team is particularly interested in concentrated sulfuric acid as a potential solvent for life. Liquid droplets of concentrated sulfuric acid build the clouds of Venus. The acid concentrations in the droplets vary from 81% to 98% acid, with the rest being composed of water.
An important item to mix into that Venusian cloud blend: Amino acids and other organics are continuously being delivered to Venus with meteoritic material.
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Morning Star initiative
Could such an aggressive solvent in the Venus clouds set the stage for alien biochemistry?
"If yes, then of course such life would be fundamentally different from life on Earth," said Pętkowski. He and colleagues are motivated to study organic chemistry in concentrated sulfuric acid, to see if such complex reacions might be occurring in the Venus cloud layers, around 30 miles to 40 miles (48 to 64 kilometers) up.
This research will also likely inform future missions to the cloud-cloaked planet. These efforts include the Venus Life Finder mission (now labeled the Rocket Lab Mission to Venus), which is scheduled to launch atop a Rocket Lab Electron rocket in early 2025, and the subsequent projects from the Morning Star Missions to Venus initiative led by MIT astrophysicist and planetary scientist Sara Seager.
Pętkowski is deputy principal investigator on the Venus Life Finder Mission Concept Study.
Objective #1 for Venus Life Finder is searching for the presence of organic material within cloud-layer particles as a function of altitude.
Early work on the scientific and technical challenges of privately funded Venus exploration was aided by the Breakthrough Initiatives, a suite of space science programs financially backed by a foundation established by entrepreneurs Julia and Yuri Milner.
"There's increasing attention on Earth's 'Evil Twin' Venus as a past, and possible current, abode of life," Pete Worden, executive director of Breakthrough Initiatives, told Space.com. "It's possible, and increasingly likely that Venus is a life-bearing world. Perhaps Earth life even originated there!"
Not universally hostile
"We have shown that concentrated sulfuric acid is not universally hostile to organic chemistry and that surprisingly, many organics are stable and soluble for months, if not longer, in this aggressive solvent," Pętkowski said.
In earlier work, the investigative team showed that other key molecules needed for life — nucleic acid bases — are stable in concentrated sulfuric acid, "advancing the notion that the Venus atmosphere environment may be able to support complex chemicals needed for life," Pętkowski added.
The stability of amino acids in concentrated sulfuric acid is an "unexpected discovery," Pętkowski said, "that further supports the notion that complex organic chemistry is possible in Venus' concentrated sulfuric acid clouds, and that it is likely that organic chemistry is in fact present in Venus clouds."
