Scientists have spent years recovering samples directly from asteroids to settle persistent questions about whether life’s chemical building blocks exist beyond Earth — and whether they arrived here from space.
A new paper has confirmed the presence of all five nucleic acid bases in material retrieved from the asteroid Ryugu by the Hayabusa2 mission. According to the report, earlier analysis of Ryugu samples had detected only one base clearly, leaving the others unaccounted for despite their presence in samples from multiple other asteroids. The new work addressed that gap directly: researchers used larger starting samples combined with higher-sensitivity testing, and the remaining bases appeared.
That fills in a specific gap, but it is not the first time these molecules have turned up off-world.
The paper’s abstract references their discovery across three different asteroids, and an early paragraph cites a 2011 paper describing nucleic acid bases in meteorites — fragments of asteroids that survived atmospheric entry. Subsequent years brought further confirmations. When NASA‘s OSIRIS-REx mission returned material from the asteroid Bennu, the same bases were present in that sample as well. Each time, the asteroids also carried closely related molecules not used by any known living organism.
The contamination question had long complicated results from meteorite studies, since atmospheric heating or contact with terrestrial life could theoretically account for what was found. Direct sample retrieval from space addresses that concern without ambiguity.
Both DNA and RNA depend on four bases each — three shared between them, plus one unique to each molecule — and the sequence of those bases along a molecular backbone is what carries genetic information. Before life as we know it existed, the ordering of bases along RNA molecules is hypothesized to have determined what chemical reactions those molecules could catalyze. The bases are not sufficient on their own to produce life, but they represent a significant part of the required chemistry.
The new paper moves beyond confirmation into something more revealing. Nucleic acid bases split into two structural categories: purines, which have two-ringed structures, and pyrimidines, which are simpler single-ring forms. Researchers pooled these two classes across multiple asteroid samples and compared their relative concentrations. They found a correlation between those ratios and the amount of ammonia present in each asteroid — a finding the researchers suggest may point toward the specific chemistry that originally produced these bases in space.
That chemical connection matters because extensive research has long sought to identify which reactions could plausibly generate nucleic acid bases under non-biological conditions. Understanding the ammonia link could bring scientists closer to reconstructing how those reactions actually operated, and by extension, how the raw materials for life on Earth came to be here at all.
The next step the paper points toward is continued analysis of the relationship between ammonia levels and base formation chemistry across asteroid samples.
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