Discovery of Uracil in Ryugu Asteroid Provides Insight into the Emergence of Life on Earth- NASA

SPACE — For the first time, scientists have discovered one of the key building blocks for RNA in an asteroid in outer space. This discovery suggests that the blueprints for life may have been brought to Earth from beyond our planet, and that rudimentary life forms also exist elsewhere in the solar system.

Japanese scientists have performed a new analysis on samples taken from the diamond-shaped asteroid Ryugu. Researchers found uracil, one of the five nucleobases that make up our genetic code, along with vitamin B3 and a number of other organic molecules on the surface of space rocks.

Analysis of meteorites found on Earth previously revealed that fallen space rocks contained five nucleobases that are essential for building life as we know it. However, scientists are not sure whether they were in the rock before it fell to Earth or if the meteorite was contaminated by our atmosphere.

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But analysis of Ryugu’s contents, taken from the surface of the asteroid, has provided important clues that the cosmos may be teeming with life-promoting molecules. The researchers published their findings March 21, 2023, in the journal Nature Communications.

“As long as uracil and other nucleobases exist in space, that means the materials for nucleic acids (DNA and RNA) exist in that environment,” lead author Yasuhiro Oba told Live Science.

The astrochemist at Japan’s Hokkaido University said it was difficult to exclude the possibility that some life forms existed in the extraterrestrial environment. Five nucleobases, namely adenine, guanine, cytosine, thymine, and uracil combine with ribose and phosphate to form DNA and RNA. The latter two are ladder-like structures that make up the genetic code of all life on Earth.

It’s the code that cells are made of, that is, DNA is unzipped and transcribed into RNA, and RNA makes proteins, and proteins in turn act as the microscopic machinery that builds and maintains cells while creating more and more copies of DNA.

To make the first detection, the Japan Aerospace Exploration Agency (JAXA) sent the Hayabusa2 spacecraft on a 322 million kilometer journey to Ryugu, a carbon-filled asteroid filled with carbon-rich organic matter. According to the researchers, most of Ryugu’s formation, which is loosely piled like a swirling mass of debris, likely originated in the same nebula that formed our solar system’s sun and planets 4.6 billion years ago.

After landing on the asteroid in 2018, Hayabusa2 scraped about 5.4 grams from Ryugu’s surface, then stored the material in an airtight container. It then glides back to Earth on a prearranged trajectory. Other building blocks for life, including 15 different amino acids, were also found in the samples it carried.

How the blueprints for life first formed on Ryugu, or in interstellar clouds and the rest of our solar system, are not well understood. Researchers believe amino acids and nucleotides can be made when interstellar ice is struck with powerful cosmic rays, breaking down the simple molecules trapped inside and rearranging them into more complex configurations. Once trapped on asteroids like Ryugu, these molecules may eventually hitch a ride to Earth via meteorite impact, where they sparked the first upsurge of life in our primordial oceans.

Ryugu isn’t the only space rock being investigated. In 2021, NASA’s OSIRIS-REx spacecraft collected rock samples from another diamond-shaped asteroid, named Bennu. When the samples returned to Earth, the signatures of the organic matter they contained provided important clues about the evolution of the solar system and its materials, as well as clues about how life arose from it. Source: LiveScience