RNA compound and vitamin B3 found in near-Earth asteroid samples

Organic molecules have been detected in samples collected by the Japanese Hayabusa2 mission from the near-Earth Ryugu asteroid. A study published in the journal Nature Communications details the findings.

Ryugu is a carbon-rich diamond-shaped asteroid measuring about a kilometer across.

“When the researchers analyzed the samples, collected from two different locations on the asteroid, they found uracil, one of the building blocks of RNA, as well as vitamin B3, or niacin – a key cofactor for metabolism in living organisms.”

Uracil is a nucleobase, or a nitrogen-containing compound. It is one of five nucleobases in DNA and RNA, the proteins and molecules that contain crucial genetic information and instructions for the cells of living organisms.

Hayabusa2 was the first mission to return a subsurface sample from an asteroid to Earth. It was collected in February 2019, and then a copper “bullet” was fired at the asteroid to create an impact crater 10 meters wide.

In previous analyses, the researchers detected amino acids and other molecules in samples from Ryugu, while uracil and niacin were also found in meteorites that fell to Earth.

“Scientists have already found nucleobases and vitamins in certain carbon-rich meteorites, but there has always been the question of contamination from exposure to the Earth’s environment,” said study lead author Yasuhiro Oba, an associate professor at Hokkaido University in Japan. in a statement.

“Since the Hayabusa2 spacecraft took two samples directly from the Ryugu asteroid and delivered them to Earth in sealed capsules, contamination can be ruled out.”

Building blocks of life in space

The researchers discovered the molecules when they soaked particles collected from Ryugu in hot water and analyzed the results using different observational methods such as liquid chromatography and mass spectrometry.

The scientists worked with samples collected from two different locations on the near-Earth asteroid Ryugu. Then, the team detected the signatures of uracil, niacin and other nitrogen-containing organic compounds.

“Other biological molecules were also found in the sample, including a selection of amino acids, amines and carboxylic acids, which are found in proteins and metabolism, respectively,” said Oba.

Together, the Ryugu sample results so far add to the growing evidence that the building blocks of life originated in space and were originally delivered to Earth billions of years ago by meteorites.

The molecules likely originally formed through photochemical reactions in ice in outer space even before our solar system existed, Oba said.

Further study of the asteroid’s composition

The concentrations of the molecules in the two samples were different, but that was probably due to exposure to the harsh environment of space.

It is possible that Ryugu was once part of a larger celestial body, such as a comet, before being broken into pieces by collisions with other space objects.

“There is no doubt that biologically important molecules such as amino acids and nucleobase(s) in asteroids/meteorites have been provided to Earth,” said Oba.

“In particular, we hope they could play a role in prebiotic evolution on early Earth.”

It’s also possible that as space rocks collide with other planets in our solar system, they could be carrying some of the same building blocks of life.

“I cannot say that the presence of such ingredients directly leads to the emergence/presence of extraterrestrial life, but at least their components, such as amino acids and nucleobases, could be present throughout space,” said Oba.

Now researchers want to know how common these molecules are in asteroids.

Fortunately, a sample from another asteroid called Bennu will be delivered to Earth in September by NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer or OSIRIS-REx spacecraft.

“The discovery of uracil in the Ryugu samples supports current theories about the source of nucleobases on early Earth,” said Oba.

“NASA’s OSIRIS-REx mission will return samples from asteroid Bennu this year, and a comparative study of the composition of these asteroids will provide more data to build these theories.”