Organic Molecules found at the Asteroid Ryugu
Hayabusa2 (Peregrine Falcon 2 in Japanese) is an asteroid sample-return mission operated by the Japanese state space agency (JAXA) [1].
It rendezvouses with Ryugu on 27 June 2018, surveyed for one year and a half then took samples. It left the asteroid in November 2019 and returned the samples to Earth on 5 December 2020 UTC. Its mission has now been extended to 2031 when it will rendezvous with 1998 KY26.
Scientists identified numerous organic molecules in the Ryugu samples. They analyzed the samples with mass spectroscopy and detected hundreds of thousands of ion signals, which they assigned to ~20,000 elementary compositions consisting of carbon, hydrogen, nitrogen, oxygen, and/or sulfur [2]. They liberated the gases in Ryugu samples by heating to 1400 degree Celsius and analyzed them. Surprisingly, fifteen amino acids were found in the asteroid. They include glycine, alanine, and α-aminobutyric acid. Amino acids are found in nature as left-handed. In the asteroid’s samples, amino acids were equally left and right-handed. This confirms the abiotic origin. Aliphatic amines (such as methylamine) and carboxylic acids (such as acetic acid) were also detected, likely retained on Ryugu as organic salts [2]. These results, mostly indicate water source.
Samples collected by Hayabusa2 contain Soluble Organic Molecules (SOM). Asteroid is exposed to the hard vacuum of space, energetic particle irradiation, heating by sunlight, and micrometeoroid impacts, but the soluble organic molecules are still preserved [2]. Minerals, contained in the asteroid, are most likely caused by the water in the parent asteroid. But the presence of SOM and amino acids provide a piece of evidence to Panspermia theory.
There is another meteorite that is in Earth named Murchison Meteorite. It fell to Murchison, Victoria, Australia [3]. 100 kilograms of material were recovered from Murchison meteorite. Scientists were compared the organic material with Murchison meteorite and found that molecular diversity of low-molecular weight compounds was lower than Murchison. It can be less however, due to minerals and their protection, Ryugu continued to contain organic compounds [2].
Surface grains on Ryugu may disperse its SOM with entry to planets. Planet entry will cause ablation and high temperature on the surface. This can cause the degradation of the molecules and all evidence of amino acids may be destroyed. However, there is a case that they can stay intact and spread SOM to planets. Therefore, SOM on C-type asteroids could be a source of organics delivered to other bodies [2].
References
[1] “In Depth | Hayabusa 2 — NASA Solar System Exploration.” https://solarsystem.nasa.gov/missions/hayabusa-2/in-depth/ (accessed Feb. 25, 2023).
[2] “Soluble organic molecules in samples of the carbonaceous asteroid (162173) Ryugu | Science.” https://www.science.org/doi/10.1126/science.abn9033 (accessed Feb. 25, 2023).
[3] “Murchison (Meteorit) — Wikipedia.” https://de.wikipedia.org/wiki/Murchison_(Meteorit) (accessed Feb. 25, 2023).
