Nagoya, Gatra.com- A key building block for life was found in the distant asteroid Ryugu — and it could explain how life on Earth began. Thereby Live Science, 22/03. Scientists have found uracil, one of the main building blocks of RNA, in the asteroid Ryugu 200 million miles away.
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 could 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 previous meteorites found on Earth reveals that falling space rocks contain five nucleobases essential for building life as we know it, but scientists are unsure whether they were there before they fell to Earth or made their way into meteorites due to contamination of our atmosphere.
But analysis of the contents of Ryugu, which was retrieved from the surface of the asteroid before it was launched back to Earth, has provided important clues that the cosmos may be full of life-promoting molecules. The researchers published their findings March 21 in the journal Nature Communications.
“As long as uracil and other nucleobases exist in space, that means they’re ingredients for nucleic acids [DNA dan RNA] exist in the environment,” lead author Yasuhiro Oba, an astrochemist at Hokkaido University in Japan, told Live Science via e-mail. “In my personal opinion, it is difficult to exclude the possibility that some form of life exists in an extraterrestrial environment.”
Five nucleobases – adenine, guanine, cytosine, thymine and uracil – combine with ribose and phosphate to form DNA and RNA, the twisted ladder-like structures that make up the genetic code of all life on Earth. It is from this code that cells are made: DNA is unzipped and transcribed into RNA; RNA makes proteins; and proteins in turn act as the microscopic machinery that builds and maintains cells while creating more copies of DNA.
To make the first detection, Japan Aerospace Exploration Agency (JAXA) sent the Hayabusa2 spacecraft on a 200 million mile (322 million kilometer) journey to Ryugu, a carbon-filled asteroid with carbon-rich organic matter. Most of Ryugu’s content, which is loosely stacked as a swirling mass of debris, likely originated in the same nebula that gave birth to our solar system’s sun and planets roughly 4.6 billion years ago, according to researchers.
After landing on the asteroid in 2018, Hayabusa2 scraped about 0.2 ounces (5.4 grams) from Ryugu’s surface, before depositing the material in an airtight container and launching itself back to Earth on a well-arranged trajectory. Other building blocks for life, including 15 different amino acids, were also found in the returned sample.
How the blueprints for life first formed on Ryugu, or in the interstellar clouds that would later give birth to it and the rest of our solar system, is 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 the 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 return to Earth in September, the signatures of the organic matter they contain may provide scientists with important clues about the evolution of the solar system and its materials, as well as clues about how life emerged from it.