Scientists Uncover Life’s Building Blocks in Ryugu Asteroid Samples

Scientists have discovered essential ingredients for DNA and RNA in samples collected from the asteroid Ryugu. This finding, announced on Monday, reinforces the idea that such building blocks may be common throughout the Solar System. The results suggest that primitive asteroids could produce and preserve molecules critical to the chemistry associated with the origin of life.

The research follows earlier findings from the asteroid Bennu, where similar elements were identified. This supports a longstanding hypothesis that life on Earth may have originated from asteroids delivering fundamental components to our planet billions of years ago. The Hayabusa-2 spacecraft embarked on its mission to Ryugu in 2014, traveling approximately 300 million kilometres (about 185 million miles) to collect samples. In 2020, it successfully returned two samples weighing 5.4 grams (under a fifth of an ounce) each to Earth.

Research published in 2023 revealed that these samples contained uracil, one of the four bases that make up RNA. Unlike DNA, which serves as a genetic blueprint, RNA acts as a crucial messenger, translating the instructions stored in DNA for biological processes. In a new study published in Nature Astronomy by a team of Japanese researchers, all five nucleobases required for both DNA and RNA were identified in the Ryugu samples. These include uracil, adenine, guanine, cytosine, and thymine.

Toshiki Koga, the study’s lead author and biochemist at the Japan Agency for Marine-Earth Science and Technology, clarified that the presence of these molecules does not imply that life existed on Ryugu. “Instead, their presence indicates that primitive asteroids could produce and preserve molecules that are important for the chemistry related to the origin of life,” Koga stated.

The study’s findings underscore the potential for carbonaceous asteroids to have contributed to the prebiotic chemical inventory of early Earth. Cesar Menor Salvan, an astrobiologist from Spain’s University of Alcala who was not involved in the research, noted that these results do not support the notion that life originated in space. However, he emphasized, “with this and the results from Bennu, we have a very clear idea of which organic materials can form under prebiotic conditions anywhere in the universe.”

The discovery of these building blocks mirrors findings from fragments returned by NASA from Bennu, as well as from meteorites such as Orgueil and Murchison. In the latest research, the Japanese team compared the quantities of each nucleobase found in various space rocks and noted that these amounts differed based on their individual histories. Notably, they identified a correlation between the ratios of nucleobases and the concentration of another essential chemical for life: ammonia.

Koga remarked, “Because no known formation mechanism predicts such a relationship, this finding may point to a previously unrecognised pathway for nucleobase formation in early Solar System materials.”

Another scientist not involved in the research, Morgan Cable from the Victoria University of Wellington in Australia, described this particular discovery as “unique.” She added, “This discovery has important implications for how biologically important molecules may have originally formed and promoted the genesis of life on Earth.”

As researchers continue to investigate the implications of these findings, the understanding of life’s origins on our planet may take on new dimensions, with asteroids like Ryugu providing crucial insights into the fundamental processes that led to the emergence of life.