This image highlights some of the organic molecules found on asteroid Ryugu. (Credit: NASA/JAXA/Dan Gallagher)
An international team of scientists has analyzed a sample of the asteroid Ryugu and found that the sample is rich with organic molecules. Organic molecules are the building blocks of all currently known forms of terrestrial life. Thus, this discovery supports the theory that asteroids may have delivered the chemical components necessary for life to Earth many, many years ago. The results of the analysis were published in the journal Science.
The sample was collected from the asteroid’s surface by Japan’s Hayabusa 2 spacecraft (led by the Japan Aerospace Exploration Agency, JAXA) on February 22, 2019 and delivered to Earth on December 6, 2020. The sample was distributed between laboratories in Japan, the United States, and Europe. The aforementioned paper presents the first organic analysis of the Ryugu sample, but the sample will continue to be studied for many years. In fact, scientists are planning to compare the sample from asteroid Ryugu to a sample from asteroid Bennu. The sample of asteroid Bennu was collected in late 2020 by NASA’s OSIRIS-Rex mission and should be delivered to Earth sometime in 2023. The OSIRIS-Rex mission is expected to return much more sample mass from Bennu than was collected from Ryugu. This sample will provide another piece of the puzzle to see if organic building blocks of life are common in a carbon-rich asteroid.
Organic molecules are a family of compounds composed of carbon combined with hydrogen, oxygen, nitrogen, sulfur, as well as other atoms. They can be made by chemical reactions that do not involve life forms, which supports the hypothesis that chemical reactions in asteroids can create some of life’s ingredients.
Many organics were found in the sample from Ryugu, as well as several kinds of amino acids. Amino acids are essential for building proteins, which can in tern be used to make enzymes. The sample also contained organics that form in the presence of liquid water (e.g., aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, nitrogen-containing heterocyclic compounds). The amino acid results from Ryugu are consistent with what has been measured for some carbon-rich meteorites that have been exposed to water in space. However, although sugars and nucleobases, key ingredients of DNA and RNA, have been discovered in carbon-rich meteorites, they have not been discovered in the sample from Ryugu. It is possible that these compounds do exist in the sample but are below the detection limits of the techniques being used to analyze the sample.
The presence of organic molecules on the asteroid’s surface suggests that the surface grains of Ryugu could be protecting these molecules despite its extremely harsh environment. Ryugu is subject to solar heating, ultraviolet radiation, and cosmic-ray radiation. Thus, organic molecules may be safely transported through the Solar System on asteroids. These organic molecules may then be dispersed as interplanetary dust particles if and when they are ejected from the asteroid, eventually making their way to the surface of planets and moons.
Source: NASA.gov