Huge cosmic breakthrough may reveal where life on Earth really came from

An artistic visualisation of the OSIRIS-REx spacecraft descending towards asteroid Bennu (Image: NASA/Goddard/University of Arizona)

The tantalising possibility that the building blocks of life on Earth were delivered from space has been strengthened by a comprehensive analysis of the sample retrieved from Asteroid Bennu. Scientists analysing the material collected by NASA’s OSIRIS-REx mission have confirmed that the dark, pristine rock contains a complete inventory of the organic molecules necessary for the formation of terrestrial biology, providing robust empirical evidence for a cosmic origin of life's chemistry.

The intriguing findings, which bolster the theory that asteroids seeded the early Earth with life’s chemical components - a process known as panspermia - reveal an unparalleled complexity within the sample.  Laboratory analysis has confirmed the presence of all five nucleobases—adenine, guanine, cytosine, thymine, and uracil—which are the fundamental molecular "letters" encoding genetic information in DNA and RNA. Additionally, 15 of the 20 amino acids used to build proteins have been identified.

A microscopic particle of asteroid Bennu (Image: NASA/University of California, Berkeley)

Crucially, the investigation detected key biological sugars. While previous meteorite studies had hinted at the presence of these compounds, the Bennu sample, returned to Earth in a sealed capsule in 2023, is the first to unambiguously show the existence of both ribose and glucose. Ribose is the essential sugar that forms the backbone of RNA, while glucose is a primary fuel source for cellular metabolism.

The discovery of ribose alongside the nucleobases is considered a pivotal moment in astrobiology. Ribose is fundamental to the so-called "RNA World” hypothesis, which proposes that early life used simpler RNA molecules to store genetic data before evolving into the more complex, double-stranded DNA structure. 

The fact that the sample contained ribose but lacked detectable amounts of deoxyribose (the sugar used in DNA) suggests the asteroid’s chemistry represents a time capsule from the early solar system’s pre-DNA chemical phase.

A mission spokesperson stated: “The Bennu sample is an exceptional archive of our solar system’s history, and its contents suggest a chemical environment conducive to forming these complex building blocks.”

Beyond the organic molecules, the sample provided overwhelming evidence of ancient aqueous processes.

Analysis of the clay minerals and iron oxides demonstrated that Bennu’s parent body hosted liquid water —specifically, salty brines— for prolonged periods in the solar system's first few million years. 

This means the organic molecules did not form in a dry vacuum but were synthesised within a warm, watery environment, akin to a natural chemical reactor.

Further adding to the scientific intrigue, the team identified a strange, nitrogen-rich polymer — a type of flexible, gum-like substance not previously observed in space rock samples.

This unique finding suggests that the asteroid may have hosted numerous complex chemical pathways that remain to be fully understood.

Ultimately, the analysis confirms that Asteroid Bennu is a remnant of an early solar system population that routinely impacted the primitive Earth. 

By proving that these bodies contained all the essential organic and structural components—genetic letters, protein building blocks, metabolic sugars, and evidence of water—the Bennu sample delivers concrete, empirical support for the theory that life’s origins were chemically primed from space.

The mission has firmly established the astronomical contribution to the terrestrial biosphere, says NASA.