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Component of RNA Found in Asteroid Ryugu Samples

A conceptual image for sampling materials on the asteroid Ryugu containing uracil and niacin by the Hayabusa2 spacecraft. Credit: NASA Goddard/JAXA/Dan Gallagher

Samples from the asteroid Ryugu collected by the Hayabusa2 mission contain nitrogenous organic compounds, including the nucleobase uracil, which is a part of RNARibonucleic acid (RNA) is a polymeric molecule similar to DNA that is essential in various biological roles in coding, decoding, regulation and expression of genes. Both are nucleic acids, but unlike DNA, RNA is single-stranded. An RNA strand has a backbone made of alternating sugar (ribose) and phosphate groups. Attached to each sugar is one of four bases—adenine (A), uracil (U), cytosine (C), or guanine (G). Different types of RNA exist in the cell: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>RNA.

Researchers have analyzed samples of asteroid Ryugu collected by the Japanese Space Agency’s Hayabusa2 spacecraft and found uracil—one of the informational units that make up RNA, the molecules that contain the instructions for how to build and operate living organisms. Nicotinic acidAny substance that when dissolved in water, gives a pH less than 7.0, or donates a hydrogen ion.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>acid, also known as Vitamin B3 or niacin, which is an important cofactor for metabolism in living organisms, was also detected in the same samples.

Photographs of samples A0106 and C0107 collected from the asteroid Ryugu, during the 1st touchdown sampling and 2nd touchdown sampling, respectively. Credit: Yasuhiro Oba, et al. Nature Communications. March 21, 2023

This discovery by an international team, led by Associate Professor Yasuhiro Oba at Hokkaido UniversityFounded in 1876 as Sapporo Agricultural College, Hokkaido University (Hokkaidō daigaku or Hokudai) is a Japanese national university in Sapporo, Hokkaido. It was selected as a Top Type university of Top Global University Project by the Japanese government.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Hokkaido University, adds to the evidence that important building blocks for life are created in space and could have been delivered to Earth by meteorites. The findings will be published today (March 21) in the journal Nature Communications<em>Nature Communications</em> is a peer-reviewed, open-access, multidisciplinary, scientific journal published by Nature Portfolio. It covers the natural sciences, including physics, biology, chemistry, medicine, and earth sciences. It began publishing in 2010 and has editorial offices in London, Berlin, New York City, and Shanghai. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Nature Communications.

“Scientists have previously found nucleobases and vitamins in certain carbon-rich meteorites, but there was always the question of contamination by exposure to the Earth’s environment,” Oba explained. “Since the Hayabusa2 spacecraft collected two samples directly from asteroid Ryugu and delivered them to Earth in sealed capsules, contamination can be ruled out.”

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Illustration of Japan’s Hayabusa2 mission to asteroid Ryugu. Credit: JAXA

The researchers extracted these molecules by soaking the Ryugu particles in hot water, followed by analyses using liquid chromatography coupled with high-resolution mass spectrometry. This revealed the presence of uracil and nicotinic acid, as well as other nitrogen-containing organic compounds.

Mass chromatograms from the first (top) and second (center) samples from asteroid Ryugu, showing the presence of uracil (red peak). They were compared to a sample of pure uracil (bottom). Credit: Yasuhiro Oba, et al. Nature Communications. March 21, 2023

“We found uracil in the samples in small amounts, in the range of 6–32 parts per billion (ppb), while vitamin B3 was more abundant, in the range of 49–99 ppb,” Oba elaborated. “Other biological molecules were found in the sample as well, including a selection of amino acids<div class="cell text-container large-6 small-order-0 large-order-1">
<div class="text-wrapper"><br />Amino acids are a set of organic compounds used to build proteins. There are about 500 naturally occurring known amino acids, though only 20 appear in the genetic code. Proteins consist of one or more chains of amino acids called polypeptides. The sequence of the amino acid chain causes the polypeptide to fold into a shape that is biologically active. The amino acid sequences of proteins are encoded in the genes. Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food.<br /></div>
</div>” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>amino acids
, amines, and carboxylic acids, which are found in proteins and metabolism, respectively.” The compounds detected are similar but not identical to those previously discovered in carbon-rich meteorites.

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The team hypothesizes that the difference in concentrations in the two samples, collected from different locations on Ryugu, is likely due to the exposure to the extreme environments of space. They also hypothesized that the nitrogen-containing compounds were, at least in part, formed from the simpler molecules such as ammonia, formaldehyde, and hydrogen cyanide. While these were not detected in the Ryugu samples, they are known to be present in cometary ice—and Ryugu could have originated as a comet or another parent body that had been present in low-temperature environments.

“The discovery of uracil in the samples from Ryugu lends strength to current theories regarding the source of nucleobases in the early Earth,” Oba concludes. “The OSIRIS-RExLaunched in 2016, the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft will help astronomers investigate how planets formed and how life began, as well as improve our understanding of near-Earth asteroids.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>OSIRIS-REx mission by NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA will be returning samples from asteroid Bennu this year, and a comparative study of the composition of these asteroids will provide further data to build on these theories.”

Reference: “Uracil in the carbonaceous asteroid (162173) Ryugu” 21 March 2023, Nature Communications.
DOI: 10.1038/s41467-023-36904-3

Funding: Japan Aerospace Exploration Agency, Deutsches Zentrum für Luft- und Raumfahrt, Centre national d’études spatiales, National Aeronautics and Space Administration, Australian Space Agency, Japan Society for the Promotion of Science

The Hayabusa2 mission was a Japanese space mission launched in 2014 with the aim of studying the asteroid Ryugu and bringing back samples to Earth. The spacecraft arrived at Ryugu in 2018 and spent over a year studying the asteroid’s surface and interior, deploying multiple landers and rovers to conduct experiments and collect data. In 2019, the spacecraft used a projectile to create a small crater on the asteroid’s surface, collecting subsurface material from the impact site. The spacecraft returned to Earth in December 2020, bringing back the first-ever subsurface samples from an asteroid. The mission provided valuable insights into the formation of the solar system and the composition of asteroids.

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Source: SciTechDaily