A sample taken from an asteroid far from Earth has confirmed that RNA nucleobases can be found in space rocks.
Analysis of house dust from the asteroid Ryugu has been found to contain uracil – one of the four nucleobases that make up RNA – in addition to niacin, a form of vitamin B3, which plays an important role in metabolism.
This adds to the growing body of evidence that the building blocks of life in space, and may have been partially supplied to Earth by asteroid bombardment early in our planet’s history.
“Scientists have already found nucleobases and vitamins in some rocks with a lot of carbon, but there is always the question of contamination when looking at the Earth’s environment,” says astronomer Yasuhiro Oba of Hokkaido University in Japan.
“Since the Hayabusa2 spacecraft took two samples from asteroid Ryugu and delivered them to Earth in sealed capsules, contamination can be avoided.”
How life began, and how widespread it might be across the Milky Way galaxy, are two questions people would love to know the answers to. One way to interrogate them is to look for life structures in space, and find ways to support them out there to down here.
As we realize more and more, there are many life-building tools out there. Those who see in the world’s clear world, and in the world’s world’s darkest days, we have made a mess in our world. And they have been found in several meteorites that entered the Earth’s atmosphere and fell to the ground.
Taken together, the evidence suggests that life forms may have been alien… but certainty is not yet in place until scientists can prevent Earth’s material from getting into the rocks after they got here.
To find out what was in the ancient samples that Hayabusa2 brought back from Ryugu, Oba and his colleagues used a new method they developed to detect and identify nucleobases in small amounts.
The team took the two samples, which were taken from different locations on the asteroid, soaked them in hot water, and subjected them to high-performance liquid chromatography coupled to electrospray ionization high-resolution mass spectrometry. This method, when applied to the Murchison meteorite that fell to Earth in 1969, yielded all five accepted nucleobases.
The various biomolecules found in Ryugu were small, but still important, the researchers believe.
“We found uracil in a few samples, in the range of 6-32 parts per billion (ppb), while vitamin B3 was abundant, in 49-99 ppb,” said Oba. “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.”
The chemical compound, which is linked to 20 amino acids previously found in Ryugu samples, is different from those found in other carbonaceous meteorites that have fallen to Earth, but they are very similar. This suggests that biomolecules may be more common in carbonaceous meteorites, and could have made the journey to Earth during the bombardment.
As for how they found the asteroids, scientists believe that nitrogen-containing compounds may have been formed from simple molecules, including formaldehyde, ammonia, and hydrogen cyanide.
This was not found in Ryugu’s samples, but it should be present if, early in its history, the asteroid or its parent group was a comet, covered in ice rich in these molecules.
Ryugu, however, is just the beginning. NASA has collected a sample from another asteroid, Bennu, and brought it to Earth for analysis. Previous research shows that it also has physical properties that are related to biological structures.
“The discovery of uracil in the Ryugu samples gives strength to current theories about the origin of nucleobases in the early Earth,” says Oba.
“NASA’s OSIRIS-REx mission will return samples from asteroid Bennu this year, and comparative studies of the composition of these asteroids will provide additional data to build on these theories.”
It seems that the material of the stars that we were made of deviated from the asteroids.
Research has been published in Nature Communications.
