Scientists have confirmed the presence of organic molecules in samples taken from the Ryugu asteroid, adding credence to the idea that the ingredients for life came to Earth via meteorite and asteroid impacts.
Ryugu is a primitive carbonaceous asteroid, a rocky remnant from the formation of the Solar System more than 4 billion years ago. Japan’s Hayabusa2 mission visited Ryugu and collected samples from its surface in 2019, giving us a great way to learn what the Solar System was like in its early stages.
The research team identified hundreds of thousands of ion signals from Ryugu samples, which they associated with numerous organic molecules, including 15 amino acids, amines, aromatic hydrocarbons and other compounds. Their research is published in the Science journal.
“The presence of prebiotic molecules on the asteroid surface despite its harsh environment caused by solar heating and ultraviolet irradiation, as well as cosmic-ray irradiation under high-vacuum conditions, suggests that the uppermost surface grains of Ryugu have the potential to protect organic molecules,” said Hiroshi Naraoka, a planetary scientist at Kyushu University in Japan, in a release of NASA Goddard Space Flight Center.
“These molecules can be transported throughout the solar system, potentially dispersing as interplanetary dust particles after being ejected from the uppermost layer of the asteroid by impacts or other causes,” Naraoka added.
One of the central questions of biochemistry is how the building blocks for life, such as amino acids, got to Earth. Organic molecules, including amino acids and nucleotides, were previously found in meteorites that fell to Earth, but they were inevitably contaminated by the environment in which they landed.
This makes Ryugu’s find very special. The Japan Space Agency’s (JAXA) Hayabusa2 probe captured clumps of dust, pebbles and gas from asteroid Ryugu in 2019 when it was nearly 200 million kilometers from Earth. In 2020, the mission delivered about 5.4 grams of asteroid samples (about a teaspoon) to Earth.
The research team noted that samples from Ryugu were exposed to space and related conditions, from micrometeorite impacts to heating from the Sun.
“The presence of prebiotic molecules on the asteroid surface suggests that these molecules can be transported throughout the Solar System,” the team notes in their new paper.
NASA’s OSIRIS-REx mission is currently returning from asteroid Bennu, where it performed a similar sampling operation.
“We will do a direct comparison of the samples from Ryugu and the sample from asteroid Bennu when NASA’s OSIRIS-REx mission returns it to Earth in 2023,” said study co-author Jason Dworkin, an astrochemist at NASA’s Goddard Space Flight Center, in the release.“OSIRIS-REx is expected to return much more sample mass from Bennu and will provide another important opportunity to look for trace organic building blocks of life in a carbon-rich asteroid.”
Comparing the chemical composition of the two asteroids will reveal similarities and differences between the two rocks and help scientists fill in the gaps in our understanding of the formation of the Solar System.