In samples taken by Japan’s Hayabusa2 mission from the near-Earth asteroid Ryugu, organic compounds have been found. Researchers detected uracil, one of the RNA’s building blocks, as well as vitamin B3, or niacin, in the samples they took from two distinct spots on the asteroid (a key cofactor for metabolism in living organisms).
A nucleobase, or substance containing nitrogen, is uracil. It is one of the five nucleobases that make up DNA and RNA, the proteins and molecules that hold the genetic data and instructions vital for living species’ cells. The results of the study were published in the Tuesday issue of Nature Communications. Ryugu is a diamond-shaped, carbon-rich asteroid that is roughly 3,000 feet (1 km) wide. The first mission to bring back an asteroid surface sample was Hayabusa2.
A 33-foot (10-meter) wide impact crater was made by the Japanese Aerospace Exploration Agency mission after it took one sample from the asteroid’s surface and fired a copper “bullet” into it. In July 2019, a sample was taken from this crater. The sample was then delivered to Australia by Hayabusa2 during a flyby of Earth in December 2020.
Earlier tests of Ryugu’s samples revealed the presence of amino acids and other compounds, while meteorites that crashed to Earth have also been found to contain uracil and niacin.
“Scientists have previously found nucleobases and vitamins in certain carbon-rich meteorites, but there was always the question of contamination by exposure to the Earth’s environment,” said lead study author Yasuhiro Oba, associate professor at Hokkaido University in Japan, in a statement. “Since the Hayabusa2 spacecraft collected two samples directly from asteroid Ryugu and delivered them to Earth in sealed capsules, contamination can be ruled out.”
Building blocks of life in space components of life in space
When particles taken from Ryugu were bathed in hot water and the findings were examined using several observational techniques, including liquid chromatography and mass spectrometry, the researchers detected the compounds. Then, the scientists found uracil, niacin, and other organic nitrogen-containing chemical signatures.
“Other biological molecules were found in the sample as well, including a selection of amino acids, amines, and carboxylic acids, which are found in proteins and metabolism, respectively,” Oba said.
The results from Ryugu’s samples collectively add to the mounting evidence that the elements of life were first brought to Earth by meteorites billions of years ago from space. Before our solar system even existed, the molecules most likely first developed by photochemical reactions in ice in deep space, according to Oba.
Further asteroid composition research
The molecules’ concentrations in the two samples varied, but this was probably caused by their exposure to space’s harsh environment. It’s conceivable that Ryugu formerly belonged to a larger celestial body, such as a comet, before being fragmented by impacts with other space objects.
“It is no doubt that biologically important molecules such as amino acids and a nucleobase(s) in asteroids/meteorites have been provided to the Earth,” Oba said. “In particular, we expect they might play a role in prebiotic evolution on the early Earth.”
It’s also conceivable that some of the same components of life may have been transported by asteroids that collided with other planets in our solar system.
“I cannot say 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 may be present everywhere in space,” Oba said.
Scientists are now interested in learning how prevalent these chemicals are in asteroids. Thankfully, NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx, spacecraft will bring a sample from another asteroid named Bennu to Earth in September.
“The discovery of uracil in the samples from Ryugu lends strength to current theories regarding the source of nucleobases in the early Earth,” Oba said. “The OSIRIS-REx mission by NASA will be returning samples from asteroid Bennu this year, and a comparative study of the composition of these asteroids will provide further data to build on these theories.”