Uracil, one of the building blocks of life, found on Ryugu asteroid

Uracil, one of the building blocks of life, found on Ryugu asteroid


In addition to detecting uracil, one of the building blocks of RNA, the analysis of samples taken by the Japanese Hayabusa2 probe found vitamin B3. A finding that supports the theory that life on our planet could have an extraterrestrial origin

The asteroid RyuguJAXA

The meteorites that have fallen on Earth have allowed scientists to find out the composition of asteroids, investigate the formation of the Solar System and develop hypotheses about the origin of life on Earth, since it is believed that some elements that allowed meteorites to emerge The first organisms have extraterrestrial origin, that is, they could have reached our planet through these celestial bodies.

The dream of going to an asteroid, albeit with a robotic spacecraft, to analyze it indefinitely. situ (As has happened with the American DART mission, which on September 26 managed to divert the trajectory of Dimorphos) and the Japanese Hayabusa2 (which collected two samples in Ryugu and brought them to Earth) has become a reality and this Tuesday coincides with the publication of several studies on these two missions led respectively by NASA and JAXA, the Japanese space agency.

On the one hand, the monitoring for a month with the VLT (Very Large Telescope) terrestrial telescope of the European Southern Observatory (ESO) of the evolution of the debris generated after the impact of DART in Dimorphos has allowed two teams of scientists to study how its surface has changed after the collision and try to make a list of the elements that compose it, respectively. Studies have been published in Astronomy & Astrophysics.

In other research published today in Nature Communicationsa Japanese team reveals that the Ryugo asteroid visited by the Japanese probe Hayabusa2. contains important organic elements for life, in particular uracil and vitamin B3 (also called niacin or nicotinic acid), a result that supports the idea that these elements are created in space, and could have reached Earth via meteorites that fell to the surface.

Uracil is one of the informational units that make up RNA, a molecule similar to DNA that enables protein synthesis. In the same Ryugu samples, vitamin B3 or niacin, which is an important element for the metabolism of living organisms, was also detected.

“Scientists had previously found nucleobases and vitamins in certain carbon-rich meteorites, but there was always the question of whether the terrestrial environment could have contaminated those rocks. Since the ship Hayabusa2 collected two samples directly from the Ryugu asteroid and brought them to Earth in sealed capsules, contamination can be ruled out,” explained Yasuhiro Oba, a professor at Hokkaido University and leader of this research.

As Jesús Martínez-Fras, a CSIC planetary geologist with no connection to this study, reviews, the first detection of uracil dates back to 1979 and it was already known that this element can form in space: “The discovery of organic compounds, even complex ones, in meteorites is becoming more frequent. The most relevant article, in my opinion, on this subject was led by Oba in 2022, when they detected all the nucleobases (fundamental bricks of life, but not life, eye)”.

Regarding vitamin B3 or niacin, “Sandra Pizzarello discovered it in 2001 in the Tagish Lake meteorite and it has since been detected in other studies. Simulations have also been made indicating that it can form in interstellar ice, but that I know has not been detected”.

According to Oba, in the Ryugu samples they found uracil in small amounts, in the range of 6 to 32 parts per billion, while vitamin B3 was more abundant, in the range of 49 to 99 parts per billion. “Other biological molecules were also found in the sample, including a selection of amino acids and carboxylic acids, which are found in protein and metabolism, respectively.” The detected compounds, he adds, are similar but not identical to those previously discovered in carbon-rich meteorites.

the researchers found differences in the concentrations of uracil and vitamin B3 in the two samples that the ship collected in two different locations. A difference that they attribute to exposure to the extreme environment that is space.

Diagram of the elements found in the Ryugu asteroid by the Hayabusa2 probe
Diagram of the elements found in the Ryugu asteroid by the Hayabusa2 probeNASA Goddard/JAXA/Dan Gallagher

Jesús Martínez-Fras considers the role of these molecules “crucial” in the formation of life on Earth: “It is estimated that between 70 and 100 tons of cosmic dust reaches Earth, mainly ordinary and carbonaceous chondrites. In my opinion, It must have played a fundamental role in triggering, once on Earth, the emergence of life.”

From his point of view, “the detection of complex molecules already formed in space indicates that we need to better understand and go much deeper into the processes that give rise to them. In this sense, I believe that, in addition to radiolysis processes, the existence and the recent discovery of geological activity in asteroids and comets”.

From Ryugu’s analysis, Martínez-Fras draws two conclusions: “Firstly, we must not rule out the role played by the entry of extraterrestrial organic material for the emergence of life on Earth. And on the other hand, opens the door for us to take this into account on other planets and moons, since we should be cautious if, for example, we find organic compounds of this type on Mars since they could be false positives, that is, they would not be Martian organic compounds, but rather from meteorites”.

Another spacecraft, NASA’s OSIRIS-REx, will return to Earth on September 24 samples of the asteroid Bennu, whose composition could be compared to that of Ryugu and offer more evidence to support theories about how life arose on Earth. .

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