RNA 'life' building blocks have been found on the Ryugu asteroid

Uracil, an important building block for RNA and vitamin B3, has been identified in samples recovered from the distant asteroid Ryugu.
Christopher McFadden
Life-building molecules have been found on a distant asteroid
Life-building molecules have been found on a distant asteroid


A new study has found that uracil, one of the building blocks necessary to form RNA and vitamin B3 (an essential cofactor for metabolism in terrestrial life), has been detected in samples collected from the near-Earth asteroid Ryugu, according to a paper published in Nature Communications.

According to the research, this could mean carbon-rich asteroids brought nucleobases like uracil to Earth from an extraterrestrial origin.

Ryugu, in case you are unaware, is a near-Earth asteroid between Earth and Mars. It is a dark and rocky object that measures about one kilometer in diameter and orbits the Sun every 16 months.

In 2018, the Japanese spacecraft Hayabusa2 visited Ryugu and conducted a series of scientific observations and experiments, including collecting samples of the asteroid's surface material and deploying small rovers and landers to explore its surface. The study of Ryugu and its composition is expected to provide insights into the early Solar System and the origins of life on Earth.

In December 2020, the Hayabusa2 spacecraft brought samples back to Earth from two landing sites on Ryugu, each of which is believed to have had a unique history.

Yasuhiro Oba and coworkers examined samples from the asteroid Ryugu's two landing sites using recently created small-scale analytical techniques.

Niacin (vitamin B3), uracil, and other organic molecules believed to be crucial for synthesizing additional complex organic molecules were also found.

These molecules could have influenced the ultimate emergence of the first life on Earth. The same study team had previously discovered them in meteorites found on Earth, but their discovery in pristine samples returned from Ryugu points to an extraterrestrial origin.

RNA 'life' building blocks have been found on the Ryugu asteroid
A conceptual image for sampling materials containing uracil and vitamin B3 on the asteroid Ryugu by the Hayabusa2 spacecraft.

The authors hypothesize that these substances may have been produced by photochemical processes in interstellar ice, resulting in their integration into asteroids during the solar system's formation. Over millions of years, UV and cosmic rays may have further modified them. The authors also speculate that delivering these compounds to Earth by meteorite impact may have been crucial in the emergence of early life's genetic processes.

It is important to note, however, that it is also very likely that such organic molecules developed naturally here on Earth, so much so that many scientists believe that invoking extraterrestrial introduction of life (or its building blocks) to our planet only "muddy the waters" of our attempt to understand the origins of life on Earth.

If, as it appears, these molecules are commonplace throughout the Solar System, then it is a good bet they could also have been created using similar processes natively here on Earth.

You can view the study for yourself in the journal Nature Communications.

Study abstract:

"The pristine sample from the near-Earth carbonaceous asteroid (162173) Ryugu collected by the Hayabusa2 spacecraft enabled us to analyze the pristine extraterrestrial material without uncontrolled exposure to the Earth’s atmosphere and biosphere. The initial analysis team for the soluble organic matter reported the detection of a wide variety of organic molecules, including racemic amino acids, in the Ryugu samples. Here we report the detection of uracil, one of the four nucleobases in ribonucleic acid, in aqueous extracts from Ryugu samples. In addition, nicotinic acid (niacin, a B3 vitamer), its derivatives, and imidazoles were detected in search for nitrogen heterocyclic molecules. The observed difference in the concentration of uracil between A0106 and C0107 may be related to the possible differences in the degree of alteration induced by energetic particles such as ultraviolet photons and cosmic rays. The present study strongly suggests that such molecules of prebiotic interest commonly formed in carbonaceous asteroids, including Ryugu, and were delivered to the early Earth."

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