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Organic molecules have been detected in samples collected by Japan’s Hayabusa2 mission from the near-Earth asteroid Ryugu.
“When the researchers analyzed samples collected from two different locations on the asteroid, they found uracil, one of the building blocks of RNA, and vitamin B3, or niacin (an important co-factor for metabolism in living things).
Uracil is a nucleobase or nitrogen-containing compound. It is one of the five nucleobases in DNA and RNA, the proteins and molecules that carry genetic information and instructions important to living cells.
A study detailing the findings was published Tuesday in the journal Natural communication.
Ryugu is a carbon-rich, diamond-shaped asteroid about 3,000 feet (1 kilometer) across. Hayabusa2 is the first mission to return a subsurface sample from an asteroid to Earth.
The Japanese Aerospace Exploration Agency collected a sample from the asteroid’s surface in February 2019 and then fired a copper “bullet” into the asteroid to create a 33-foot (10-meter) wide impact crater. A sample was collected from this pit in July 2019. Later, Hayabusa2 flew back to Earth and landed the sample in Australia in December 2020.
In previous analyses, researchers found amino acids and other molecules in samples from Ryukyu, while uracil and niacin have been found in meteorites that have fallen to Earth.
“Scientists have previously found nucleobases and vitamins in some carbon-rich meteorites, but there has always been the question of contamination by exposure to Earth’s environment,” said Yasuhiro Oba, an associate professor at Hokkaido University in Japan, in a statement. “Because the Hayabusa2 spacecraft collected two samples directly from the asteroid Ryugu and delivered them to Earth in sealed capsules, contamination could be ruled out.”
The researchers discovered the molecules when they soaked particles collected from Ryuku in hot water and analyzed the results using various monitoring methods, such as liquid chromatography and mass spectrometry.
Later, the team detected signatures of uracil, niacin, and other nitrogen-containing organic compounds.
“Other biological molecules were found in the sample, including amino acids, amines and carboxylic acids found in proteins and metabolites, respectively,” Oba said.
Overall, the findings so far from Ryugu’s samples add to the evidence that the building blocks of life originated in space and were delivered to Earth billions of years ago by meteorites.
Molecules may have first formed through photochemical reactions in space ice before our solar system existed, Oba said.
The concentration of molecules in the two samples is different, but that could be due to exposure to the harsh environment of space. Ryugu may have been part of a larger celestial body, such as a comet, that was 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 meteorites/meteorites have been delivered to Earth,” Oba said. “In particular, we expect that they may have played a role in prebiotic evolution on early Earth.”
As space rocks collided with other planets in our solar system, they may have carried similar blocks of life.
“I can’t say that the presence of such substances directly leads to the origin/existence of extraterrestrial life, but at least their components like amino acids and nucleobases are probably everywhere in space,” Oba said.
Now, researchers want to know how common these molecules are in asteroids. Fortunately, a sample of another asteroid named Bennu will be delivered to Earth in September by NASA’s Origin, Spectral Description, Resource Identification, Conservation-Regolith Explorer, or OSIRIS-REx spacecraft.
“The discovery of uracil in samples from Ryukyu lends strength to current theories regarding the origin of nucleobases on the early Earth,” Oba said. “NASA’s OSIRIS-REx mission will return samples from the asteroid Bennu this year, and a comparative study of the composition of these asteroids will provide additional data to develop these theories.”