Samples taken from the near-Earth asteroid 162173 Ryugu continue to provide scientists with important insights. This time, it is about the possibility of the beginning of life on earth.
In December 2014, the Japan Aerospace Exploration Agency (JAXA) launched Hayabusa 2 on a return mission to collect samples from the carbon-rich asteroid Ryugu. After rendezvous with the asteroid in June 2018, Hayabusa2 surveyed and sampled the asteroid over her 16 months.
Hayabusa 2 delivered an extraterrestrial payload to Earth in December 2020, collecting a total of 0.2 ounces (5.4 g) of pristine sample during two touchdown operations to the asteroid. A previous analysis of the sample revealed the oldest material identified so far. Now Space Rock has abandoned many of its secrets.
An international research team led by Hokkaido University in Japan analyzed the samples using high-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (HPLC/ESI-HRMS). This powerful tool enables the molecular level analysis of complex substances, especially nucleobases, which researchers have sought.
Nucleobases are nitrogen-containing compounds that can form nucleosides, the building blocks of nucleotides that are part of DNA and RNA. The nucleobases of DNA are cytosine, guanine, adenine, and thymine. Uracil is found in RNA that provides the instructions for building organisms. These five nucleobases are called “canonical” because they are the basic units of the genetic code.
“Scientists had previously discovered nucleobases and vitamins in certain carbon-rich meteorites, but there was always the problem of contamination from exposure to the global environment,” said Yasuhiro Ohba, lead author of the study. says. “Because the Hayabusa2 spacecraft collected two samples directly from the asteroid Ryugu and delivered them to Earth in a sealed capsule, contamination can be ruled out.”
The researchers hoped that finding the nucleobases would help them better understand their role in prebiotic evolution, a stage of evolution thought to have occurred before life appeared on Earth.
Analysis of asteroid samples showed the presence of uracil in addition to nicotinic acid, a form of vitamin B3 also known as niacin, and other nitrogen-containing organic compounds.
“Uracil was detected in small amounts in the sample, ranging from 6 to 32 ppb, while vitamin B3 was more abundant, ranging from 49 to 99 ppb,” Oba said. “Other biomolecules were also found in the samples, including a selection of amino acids, amines and carboxylic acids found in proteins and metabolism, respectively.”
The compounds found by the researchers are similar, but not identical, to compounds previously found in meteorites.
Researchers hypothesize that the nitrogen-containing compounds likely formed from simple molecules such as ammonia, formaldehyde, and hydrogen cyanide. These molecules were not detected in Ryugu samples, but are present in the ice found on the comet. Researchers believe that Ryugu may have originated in a cold environment as a comet or other planetary body. shed more light on
“The discovery of uracil in samples from Ryugu gives strength to current theories about the origin of nucleobases on the early Earth,” Ohba said.
The researchers hope to compare their results with those obtained from samples collected by NASA’s OSIRIS-REx spacecraft, which is scheduled to reach Earth in September 2023. 2020.
“NASA’s OSIRIS-REx mission is scheduled to return samples from asteroid Bennu this year, and comparative studies of the compositions of these asteroids will provide further data to build on these theories.” Oba said.
The study was published in a journal Nature Communications.
Source: Hokkaido University
