Astronomical observations have shown that polycyclic aromatic hydrocarbons (PAHs) are abundant and widespread in the interstellar medium. A PAH molecule consists of several adjacent aromatic rings terminated with hydrogen. In the new study, scientists conducted laboratory isotope analysis of PAHs in samples of the asteroid Ryugu and meteorite Murchison collected by JAXA’s Hayabusa2 spacecraft. They argue that at least some of the Ryugu PAHs formed in cold interstellar clouds and therefore must be older than our solar system.
This image of asteroid Ryugu was taken on June 26, 2018 by the Telescopic Optical Navigation Camera (ONC-T) aboard JAXA’s Hayabusa 2 spacecraft from a distance of 13.7 miles (22 km).Image provided by: JAXA / University of Tokyo / Kochi University / Rikkyo University / Nagoya University / Chiba Institute of Technology / Meiji University / University of Aizu / AIST
PAHs contain about 20% of the carbon in the interstellar medium.
These can be produced in the circumstellar environment (temperatures above 1000 K), in cold interstellar clouds (temperatures around 10 K), or by the processing of carbon-rich dust particles.
“PAHs are organic compounds composed of carbon and hydrogen that are common on Earth but also occur in celestial bodies such as asteroids and meteorites,” said study co-author and director of the Western Australian Center for Organic Isotope Geochemistry. said researcher Professor Kriti Grice. Curtin University.
“We conducted controlled combustion experiments on plants in Australia and found that PAHs found in debris from the asteroid Ryugu returned to Earth by a Japanese spacecraft in 2020, and comparable to the Murchison meteorite that landed in Australia in 1969. I compared them physically.”
“We analyzed the bonds between light and heavy carbon isotopes in PAHs to reveal the temperatures at which they form.”
“Selected PAHs from Ryugu and Murchison were found to have different characteristics, with smaller ones probably forming in cold outer space and larger ones probably forming in warmer regions such as near stars or inside celestial bodies. It is thought to have been formed in the environment.”
A model of the molecular structure of ribose and an image of the Murchison meteorite. Image credit: Yoshihiro Furukawa.
“Understanding the isotopic composition of PAHs can help elucidate the conditions and environments in which these molecules were formed, providing insight into the history and chemistry of astronomical objects such as asteroids and meteorites,” says the study. said Dr. Alex Holman, co-author and fellow Westerner. Australian Center for Organic and Isotopic Geochemistry at Curtin University.
“This research gives us valuable insight into how organic compounds form extraterrestrially and where in the universe they come from.”
“Through the use of high-tech methods and creative experiments, we show that select PAHs on asteroids can form even in cold space.”
of result Published in this week’s magazine science.
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Sarah S. Zeichner other. 2023. Polycyclic aromatic hydrocarbons in Ryugu samples formed in the interstellar medium. science 382 (6677): 1411-1416; doi: 10.1126/science.adg6304
Source: www.sci.news
