Scientists Find Organic Matter in Samples from Asteroid Ryugu, Throwing Light on Possible Source of Ingredients for Life on Earth

The Yomiuri Shimbun

16:49 JST, February 24, 2023

Samples from the Ryugu asteroid that were brought back by the Hayabusa2 space probe contain various organic substances, according to papers by two research teams published in the journal Science on Friday.

A team of Kyushu University and other researchers found that the samples contained about 20,000 kinds of organic matter, including amino acids, while a team of Hiroshima University and other researchers found a large amount of black organic matter that is insoluble in acid.

It is possible that such diverse organic matter was brought to the early Earth via asteroids like Ryugu, leading to the emergence of life, scientists said.

The papers by the two teams bring together the major findings of a total of eight teams that have been working on the initial analysis of the Ryugu samples.

A Japanese, U.S. and European team, led by Prof. Hiroshi Naraoka of Kyushu University’s Department of Earth and Planetary Sciences, analyzed the Ryugu samples to identify 20 kinds of amino acids among about 20,000 kinds of organic matter, including five kinds of amino acids that are the raw materials of proteins needed for life.

Even with the same constituent elements, amino acids have different kinds of structures called “right-handed” and “left-handed.” The left-handed structure is found in most living organisms on Earth. Since the amino acids found in this study had equal amounts of both structures, it is certain that the amino acids were created in space.

Meanwhile, the other team led by Hiroshima University Prof. Hikaru Yabuta, a specialist in cosmochemistry, found a volume of black organic matter with a complex molecular structure in the samples. The team believes that this organic matter may have been formed on a parent body of water-rich Ryugu.

“It is possible that such organic matter showered onto the early Earth and became material for life,” Yabuta said.

Yokohama National University Emeritus Prof. Kensei Kobayashi said, “There are believed to have been more materials on asteroids immediately after the birth of the solar system than there are today, and they may have supplied the Earth and other celestial bodies with organic matter that could have become the ingredients for life.”