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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 the samples, which were 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 in metabolism in living things).
Uracil is a nucleobase, or nitrogen-containing compound. It is one of the five nuclear bases in DNA and RNA, the proteins and molecules that contain genetic information and instructions crucial to the cells of living organisms.
A detailed study of the results was published Tuesday in the journal Nature Communications.
Ryugu is a diamond-shaped, carbon-rich asteroid about 3,000 feet (1 kilometer) across. Hayabusa2 was the first mission to return a subsurface sample from an asteroid to Earth.
The Japan Aerospace Exploration Agency mission collected one sample from the asteroid’s surface in February 2019, then fired a copper “bullet” into the asteroid to create a 33-foot (10-meter) wide impact crater. A sample was collected from this crater in July 2019. Hayabusa2 then flew over Earth and dropped the sample in Australia in December 2020.
In previous analyses, the researchers detected amino acids and other molecules in the Ryugu samples, while uracil and niacin were also found in meteorites that landed on Earth.
“Scientists have previously found nuclear bases and vitamins in some carbon-rich meteorites, but there has always been the issue of contamination through exposure to the Earth’s environment,” study senior author Yasuhiro Ohba, an associate professor at Hokkaido University in Japan, said in a statement. “Since the Hayabusa2 spacecraft collected two samples directly from the asteroid Ryugu and delivered them to Earth in sealed capsules, contamination can be ruled out.”
The researchers detected the particles when they soaked particles collected from Ryugu in hot water and analyzed the results using various observational methods, such as liquid chromatography and mass spectrometry.
Next, the team discovered fingerprints 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 found in proteins and metabolites, respectively,” Ohba said.
Taken together, the results from the Ryugu samples 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.
Ohba said the molecules were likely originally formed through photochemical reactions in ice in outer space before our solar system existed.
The concentrations of particles in the two samples were different, but that was likely due to exposure to the harsh space environment. It is possible that Ryugu was once part of a larger celestial body, such as a comet, before it was broken into pieces by collisions with other space objects.
“There is no doubt that biologically important molecules such as amino acids and nuclear base(s) in asteroids/meteorites have been provided to Earth,” Ohba said. “In particular, we speculate that they may play a role in the evolution of prebiotics on the early Earth.”
It’s also possible that as space rocks collided with other planets in our solar system, they may have been carrying some of the building blocks for life.
“I can’t say that the presence of such components directly leads to the emergence / existence of extraterrestrial life, but at least its components such as amino acids and nucleic bases may be present everywhere in space,” Ohba said.
Now, the researchers want to know how common these particles 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 samples from Ryugu strengthens current theories regarding the source of nuclear bases in the early Earth,” Ohba said. “NASA’s OSIRIS-REx mission will return samples from Bennu this year, and a comparative study of the composition of these asteroids will provide more data to build on these theories.”
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