On Dec. 8, 2020, a capsule from the Japan Aerospace Exploration Agency (JAXA) touched down carrying samples from asteroid Ryugu.
Unlike meteorites that slam into Earth and become contaminated through contact with the terrestrial environment and human handling, these samples arrived under completely sterile conditions.
Recently, an international team of scientists led by geochemist Yasuhiro Oba of Hokkaido University detected in the sample the complete set of five nucleobases that make up DNA and RNA — adenine, guanine, cytosine, thymine, and uracil.
The discovery indicates that the fundamental ingredients for life are not unique to our planet — they were already present in the early solar system 4.5 billion years ago. Ryugu, a carbon-rich C-type asteroid, serves as a time capsule, preserving prebiotic chemistry that predates the emergence of the first living organisms.
The discovery came from an exhaustive analysis of just 5.4 grams of rocky material. Although preliminary research had already detected uracil and several amino acids, the use of optimized analytical techniques allowed researchers to identify all five nucleobases in the sample from the asteroid, which measures roughly 3,000 feet across.
The analyzed samples reveal that Ryugu contains 3.7% carbon. While most of it resembles coal, the more scientifically significant portion consists of organic molecules that release amino acids such as glycine and alanine when they interact with water. These compounds are the building blocks of proteins, and their presence in a space rock reinforces the idea that the universe’s chemistry follows consistent, universal principles.
The researchers identified a correlation between these nitrogenous bases and ammonia. This suggests that ammonia may have acted as a catalyst for complex chemical reactions in space, allowing these molecules to form and persist inside carbonaceous asteroids over millions of years of exposure to cosmic radiation.
A Matching Discovery: Asteroid Bennu
This is not an isolated case in recent space exploration. NASA obtained identical results in 2023 with samples extracted from asteroid Bennu by the OSIRIS-REx spacecraft.
The similarity in chemical composition between the two objects strengthens the hypothesis that the presence of these DNA “letters” is a common feature of asteroids orbiting in the belt between Mars and Jupiter.
Toshiki Koga, a biogeochemist and lead author of the study, clarified that the presence of these molecules does not imply the existence of past life on the asteroid. What makes the discovery significant is the ability of these ancient objects to produce and preserve compounds that are essential to prebiotic chemistry.
Impact on the Theory of Life’s Origins on Earth
The finding does not demonstrate that life once existed on Ryugu — rather, it shows that the chemical precursors to life were present there. The results suggest that early Earth was supplied with a chemical “construction kit” delivered from space. In contact with water and Earth’s geochemical environment, these materials triggered a chain of processes known as chemical evolution.
This discovery validates decades of laboratory experiments, from Walter Löb’s work in 1913 to Stanley Miller’s landmark experiment in 1953. For a century, scientists tried to model the chemistry of celestial objects using laboratory simulations. Today, the samples from asteroid Ryugu confirm that those predictions were right.
Finding these molecular structures in deep space suggests that if life has arisen elsewhere in the universe, it likely shares a biochemical foundation similar to our own.
Humanity is drawing closer to writing the opening chapter of biological history — the one that explains how the inert matter of the cosmos became the foundation of life on Earth.
