Extraterrestrial Amino Acids: Do They Mean Life Is Common in the Universe?

The Cosmic Kitchen Where Life's Ingredients Cook

The extraterrestrial amino acid distribution has been extensively examined using carbonaceous chondrites, which are the most chemically primitive meteorites containing volatile components such as water and organic matter, particularly the Murchison meteorite since it's fall in 1969. The occurrence of extraterrestrial organic compounds is a key for understanding prebiotic organic synthesis in the universe. These space rocks aren't just random debris—they're time capsules from the early solar system, preserving chemistry that happened billions of years ago. Think of them as cosmic cookbooks, written in the language of molecules, telling us what ingredients were available when our planetary neighborhood was still forming. Currently, a total of 86 amino acids have been identified in the Murchison meteorite as α, β, γ and δ amino structures with a carbon number between C2 and C9 including dicarboxyl and diamino functional groups. The sheer diversity is mind-boggling—it's like finding an entire molecular pharmacy in a single stone. Thirty three of these amino acids are unknown in natural materials other than carbonaceous chondrites. Thus the Murchison meteorite has recently been the major source of new naturally-occurring amino acids.

When Space Rocks Became Biology's Teacher

Fifty years ago, scientists discovered protein building blocks called amino acids in the Murchison meteorite (a fragment is shown, right; isolated particles, left), which landed in Australia in 1969. Scientists confirmed in 1971 that the Murchison meteorite contained amino acids, primarily glycine, and that those organic compounds likely came from outer space. This wasn't just another scientific discovery—it was a paradigm shift that made us look up at the night sky differently. Before Murchison, life's building blocks seemed uniquely terrestrial, something special that happened only on our pale blue dot. In the decades since, amino acids and other chemical precursors to life have been uncovered in other fallen space rocks. Each new meteorite that crashes to Earth brings fresh evidence that the universe is far from sterile. It's more like a vast laboratory where complex organic chemistry happens routinely, across immense distances and time scales.

The Handedness Mystery That Puzzles Scientists

Here's where things get really weird, in a way that makes you question everything you thought you knew about chemistry. Making the case for cosmic origins of Earth's amino acids even more compelling is the fact that all of the meteorite amino acids, except glycine, favor the "left-handed" molecular structure, or chirality, that is also favored by life on Earth. The preference for left-handed amino acids was a necessary precondition for life, but just why life chose left (L-amino acids) over right (D-amino acids) is a mystery. Imagine if every coin that fell from the sky landed heads-up—that's essentially what we're seeing with these cosmic amino acids. The majority of amino acids come in mirror-image varieties, termed "left-handed" and "right-handed," but it is still a mystery as to why all life on Earth uses exclusively the left-handed version. Scientists postulate that organic- and amino acid-rich meteorites, many of which show excesses of the left-handed variety, could have seeded Earth with the molecules needed for life more than 3 billion years ago. This isn't just a coincidence—it suggests a deep connection between Earth's biology and the broader cosmos.

Recent Breakthroughs From Asteroid Visitors

The plot thickened dramatically when scientists got their hands on pristine samples from space missions. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. What's fascinating is that different parts of the same asteroid tell different stories about how amino acids form and survive. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. This shows us that water isn't just the solvent of life—it's an active participant in creating life's building blocks, even in the vacuum of space.

NASA's Treasure Trove From Asteroid Bennu

Samples returned from the B-type asteroid Bennu by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer mission enabled us to study pristine carbonaceous astromaterial without uncontrolled exposure to Earth's biosphere. Here we show that Bennu samples are volatile rich, with more carbon, nitrogen and ammonia than samples from asteroid Ryugu and most meteorites. The OSIRIS-REx mission brought back something extraordinary—completely uncontaminated space material that hasn't been tainted by Earth's atmosphere or biology. We detected amino acids (including 14 of the 20 used in terrestrial biology), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles. When you realize that 14 out of 20 of life's essential amino acids are sitting on an asteroid, it makes you wonder if the ingredients for biology are standard equipment throughout the solar system. Nitrogen-15 isotopic enrichments indicate that ammonia and other N-containing soluble molecules formed in a cold molecular cloud or the outer protoplanetary disk.

The Cosmic Assembly Line for Life's Building Blocks

A new measurement of chemical evolution suggests that amino acids filled the early universe some nine billion years before life emerged. That has important implications for understanding the origin of life and attempting to re-create it in the lab. Picture the universe as a massive chemical factory that's been running for billions of years, churning out organic molecules in stellar nurseries and planetary systems. Astronomers have since found evidence of the same molecules on other planets, in asteroids, and even in interstellar space. And that raises some interesting questions. How did molecules first form in the universe, and when did the more complex ones emerge? The answer suggests that amino acid production isn't some rare accident—it's a natural consequence of cosmic chemistry. The important take-away is that the building blocks of life have a strong link not only to processes in the asteroid, but also to those of the parent interstellar cloud.

Laboratory Experiments Recreating Cosmic Conditions

Scientists aren't content to just find these molecules—they want to understand how they form. Scientists at NASA's Goddard Space Flight Center sought to explore how amino acids and amines – their chemical cousins – may have formed by simulating a mini, cosmic evolution in the lab. The researchers made ices like those found in interstellar clouds, blasted them with radiation, and then exposed the leftover material, which included amines and amino acids, to water and heat to replicate the conditions they would have experienced inside asteroids. It's like trying to reverse-engineer a recipe by analyzing the final dish. The radiation process broke apart simple molecules. Those molecules recombined into more complex amines and amino acids, such as ethylamine and glycine. What's remarkable is how readily these complex molecules form when you recreate the harsh conditions of space—intense radiation, extreme cold, and billions of years of time.

Why Earth's 20 Amino Acids Aren't Random

Here's something that will blow your mind: the 20 amino acids that life uses aren't a random collection. The researchers discovered that life seemingly did not choose its 20 building blocks randomly. "We found that chance alone would be extremely unlikely to pick a set of amino acids that outperforms life's choice," Freeland said. It's as if someone carefully selected the perfect toolkit from a hardware store with millions of options. Using novel advances in computational chemistry, we demonstrate that the set of 20 genetically encoded amino acids has been highly influenced by natural selection. We defined an adaptive set of amino acids as one whose members thoroughly cover relevant physico-chemical properties, or "chemistry space." Sets that cover chemistry space better than the genetically encoded alphabet are extremely rare and energetically costly. This suggests that if life exists elsewhere, it might converge on similar molecular solutions.

The Universal Chemistry of Life's Foundation

Life has been using a standard set of 20 amino acids to build proteins for more than 3 billion years. It's becoming increasingly clear that many other amino acids were plausible candidates, and although there's been speculation and even assumptions about what life was doing, there's been very little in the way of testable hypotheses. The fact that life stuck with the same 20 amino acids for billions of years, despite having hundreds of alternatives available, tells us something profound about the constraints of chemistry and physics. The researchers defined a likely pool of candidate amino acids from which life drew its 20. They started with the amino acids that have been discovered within the so-called Murchison meteorite, a space rock that fell in Murchison, Victoria in Australia in September 1969. This connection between meteoritic amino acids and biological ones isn't coincidental—it's evidence of a deep, cosmic continuity in the chemistry of life.

Amino Acids as Universal Molecular Attractors

Amino acids now seem both readily available to, and a plausible chemical attractor for, life as we do not know it. Amino acids thus remain important and tractable targets for astrobiological research. Think of amino acids as molecular magnets that naturally attract other molecules to form complex structures. They're not just ingredients in the recipe of life—they're the chemistry that makes complex organization possible. Whatever can be established about the likelihood of life elsewhere in the universe using amino acids or, better yet, about the characteristics of a "life-sustaining set," is a direct and significant contribution to current astrobiology. The ubiquity of these molecules throughout the cosmos suggests that the fundamental chemistry underlying life might be more universal than we ever imagined. Astronomers have detected hydrogen cyanide and methanimine, two carbon compounds that can combine with water to make the amino acid glycine, in the Arp 220 galaxy.

The Survival Challenge in Harsh Space Environments

But finding amino acids in space is only half the story—the other half is understanding how they survive the journey. In order to confirm the results of previous experiments concerning the chemical behaviour of organic molecules in the space environment, organic molecules (amino acids and a dipeptide) in pure form and embedded in meteorite powder were exposed in the AMINO experiment in the EXPOSE-R facility onboard the International Space Station. The GC–MS results confirm that resistance to irradiation is a function of the chemical nature of the exposed molecules and of the wavelengths of the UV light. They also confirm the protective effect of a coating of meteorite powder. Space is a hostile environment—intense radiation, extreme temperatures, and vacuum conditions that would destroy most organic compounds. Yet amino acids manage to survive, sometimes protected by the very rocks that carry them. The most altered compounds were the dipeptides and aspartic acid while the most robust were compounds with a hydrocarbon chain. The MS analyses document the products of reactions, such as decarboxylation and decarbonylation of aspartic acid, taking place after UV exposure.

Implications for Life Beyond Earth

Abiotic synthesis of aromatic amino acids might be possible in the water–rock interface of Enceladus's subsurface ocean. That's only as far as Saturn. Maybe a Solar System block party is closer than we think. Saturn's moon Enceladus has liquid water beneath its icy crust, and if amino acids can form there naturally, we might be looking at a second genesis of life right in our cosmic backyard. Given the universality of chemistry in space, our results have a broader implication for the fate of organic molecules that seeded the planets as soon as they became habitable as well as for the effects of UV radiation on exposed molecules at the surface of Mars, for example. The same processes that created amino acids in meteorites are happening right now throughout the galaxy. Every star system, every planetary disk, every asteroid belt could be a factory for life's building blocks.

The Deep Time Connection to Early Life

In this new paper, researchers explain that vital pieces of our proteins (amino acids) date back four billion years—to the last universal common ancestor (LUCA) of all life on Earth. We're not just talking about recent chemistry here—we're looking at molecular structures that connect us directly to the earliest life forms on our planet. This folds into existing research, like a 2017 paper suggesting that our amino acids represent the best of the best, not just a "frozen accident" of circumstances. In the new paper, the scientists say that amino acids could have even come from different portions of young Earth, rather than from the entire thing as a uniform environment. The diversity of amino acid sources suggests that early Earth was a patchwork of different chemical environments, each contributing its own molecular gifts to the emerging biosphere.

What Amino Acid Chemistry Reveals About Planetary Habitability

The results demonstrate the important role that water plays in the formation of amino acids on the giant precursors of asteroids like Ryugu. Our solar system formed from a molecular cloud, which was composed of gas and dust that was emitted into the interstellar medium (ISM), a vast space between stars. Water isn't just essential for life as we know it—it's the medium that transforms simple organic molecules into the complex building blocks of biology. This period of liquid water (termed aqueous alteration) enabled many reactions to occur, including Strecker synthesis and Formose-like reactions, the result being the production of new organic material, including amino acids. The same process also changed the rocky materials from their original minerals to new secondary minerals, such as phyllosilicates, carbonates, Fe-oxides and Fe-sulfides. Every water-bearing world becomes a potential laboratory for prebiotic chemistry, turning simple starting materials into the molecular foundation for life.

The Chemical Evolution Timeline

After several millions of years, the planetesimals began to freeze, as the radioactive material was used up. Later catastrophic collisions and interaction with the solar systems planets broke up the large bodies and sent their asteroidal and cometary fragments close to Earth. Further impact events have since delivered fragments of these asteroids and comets to the Earth's surface, supplying the Earth with large quantities of organic material, including amino acids, over the course of its history. This isn't a story about one-time events—it's about a continuous delivery system that has been operating for billions of years. Earth has been receiving regular shipments of cosmic chemistry, each meteorite fall adding to the molecular inventory available for life. The bombardment that once seemed destructive now appears to have been constructive, seeding our planet with the very molecules that would eventually become organized into living systems.

Modern Evidence From Space Missions

As it exploded, pieces of the rock that survived the journey – the Tarda meteorites – were quickly collected, and earlier this year, Dr. Rachel Smith procured a sample for the Museum. Like the other unusual meteorites with amino acids, Tarda could hold important clues to the earliest chemistry that eventually led to the origin of life. Every new meteorite that falls is like receiving a letter from deep space, written in the language of molecules. Some extraterrestrial amino acids are identical to those on Earth, while many are not found anywhere in our biosphere, making them uniquely space-borne, and many have yet to be fully identified and named. These unique space-borne amino acids represent alternative evolutionary paths that chemistry could have taken—they're like discovering new colors in the spectrum of molecular possibility. Classified as a carbonaceous chondrite, Tarda is among the most primitive and important meteorites in that it preserves within it the exact material left over from the formation of the solar system approximately 4½ billion years ago.