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.
Provided by
NASA's Goddard Space Flight Center
