Uracil in the carbonaceous asteroid (162173) Ryugu

Area of Science:

• * Astrobiology
• * Organic Geochemistry
• * Planetary Science

Background:

• * Pristine asteroid samples from (162173) Ryugu, collected by the Hayabusa2 mission, offer a unique window into extraterrestrial organic matter.
• * Previous analyses revealed diverse organic molecules, including racemic amino acids, in Ryugu samples.
• * Nitrogen-containing heterocyclic molecules are crucial for understanding the origins of life.

Purpose of the Study:

• * To detect and identify nucleobases and other nitrogen heterocyclic molecules in aqueous extracts of Ryugu samples.
• * To investigate the potential delivery of prebiotic molecules to early Earth via carbonaceous asteroids.
• * To explore the influence of space weathering on the distribution of organic compounds.

Main Methods:

• * Analysis of aqueous extracts from Ryugu samples using advanced analytical techniques.
• * Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) for molecular identification.
• * Investigation of sample alteration due to energetic particle exposure.

Main Results:

• * Detection of uracil, a fundamental nucleobase of ribonucleic acid (RNA).
• * Identification of nicotinic acid (niacin) and its derivatives, along with various imidazole compounds.
• * Observed variations in uracil concentration potentially linked to space weathering effects (UV photons, cosmic rays).

Conclusions:

• * Carbonaceous asteroids like Ryugu are significant sources of prebiotic molecules, including nucleobases.
• * These extraterrestrial organic compounds likely contributed to the chemical inventory of early Earth.
• * The findings support the hypothesis of extraterrestrial delivery of life's building blocks.