First look at Ryugu asteroid sample reveals it is organic-rich

According to preliminary research conducted by a NASA and international team using a surface sample brought to Earth by Japan's Hayabusa2 mission, asteroid Ryugu has a wide variety of organic compounds. The finding lends more credence to the theory that the list of molecular elements required for life included organic material from space.

All known types of terrestrial life are composed of organic molecules, which are a diverse range of substances made of carbon mixed with hydrogen, oxygen, nitrogen, sulfur, and other atoms. The idea that chemical processes in planets can create some of the components of life is supported by the fact that organic compounds can also be produced by chemical processes that do not involve life.

Several different types of amino acids were among the prebiotic organics identified in the sample. Prebiotic chemistry is the study of the substances and processes that may have given birth to life. Terrestrial living uses specific amino acids frequently as building blocks for proteins. Proteins are necessary for living because they are used to create enzymes that speed up or control chemical processes as well as to create structures of all sizes, including hair and muscles. The Ryugu sample also contained a variety of organic compounds that develop when liquid water is present, such as aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and heterocyclic compounds that contain nitrogen.

According to Hiroshi Naraoka of Kyushu University in Fukuoka, Japan, "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 shield organic molecules. "These molecules can be expelled from the top layer of the asteroid by impacts or other sources and carried throughout the solar system, possibly spreading as interplanetary dust particles."

An article about this study that was published online on February 23 in Science has Naraoka as its main author.

According to co-author Jason Dworkin of NASA's Goddard Space Flight Center in Greenbelt, Maryland, "so far, the amino acid findings from Ryugu are mostly compatible with what has been seen in certain kinds of carbon-rich (carbonaceous) meteorites that have been subjected to the most water in space."

However, according to co-author of the article and Daniel Glavin of NASA Goddard, "sugars and nucleobases (components of DNA and RNA) which have been found in some carbon-rich meteorites, have not yet been identified in samples returned from Ryugu." Given the comparatively tiny sample mass that is accessible for analysis, it is conceivable that these chemicals are present in the asteroid Ryugu but are below our analytical detection limits.

The samples were taken on February 22, 2019, and they were returned to Earth on December 6, 2020, by the Hayabusa2 mission. They were removed in Japan in July 2021, and Goddard conducted analysis in the following fall. The worldwide soluble organic analysis squad was given a very tiny sample (30 milligrams, or about 0.001 ounce). The sample was processed (like tea) in many various liquids in Japan and examined with a wide array of tools akin to those used in a forensics lab in Japan, Goddard, and Europe.

The Ryugu sample underwent its first organic analysis in this effort, and it will continue to be examined for years. When the sample from the asteroid Bennu is brought back to Earth by NASA's OSIRIS-REx mission in 2023, "we will directly compare the samples from Ryugu and the sample from asteroid Bennu," said Dworkin. Another significant chance to search for traces of the organic building blocks of life in a carbon-rich asteroid will be provided by OSIRIS-REx, which is anticipated to return much more sample mass from Bennu.