ICE CHEMISTRY ON OUTER SOLAR SYSTEM BODIES: ELECTRON RADIOLYSIS OF N₂-, CH₄-, AND CO-CONTAINING ICES

Area of Science:

• Astrochemistry
• Planetary Science
• Organic Chemistry

Background:

• Surface ices on outer Solar System bodies are processed by radiation.
• This radiation processing is hypothesized to create complex organic molecules.
• These molecules may contribute to the observed colors of icy bodies.

Purpose of the Study:

• To analyze refractory materials produced from electron irradiation of simple ices.
• To simulate cosmic ray bombardment effects on Pluto's surface ices.
• To identify the composition and chemical nature of radiation-produced organics.

Main Methods:

• Electron bombardment of low-temperature N2-, CH4-, and CO-containing ices.
• Analysis of refractory materials using Fourier-transform infrared spectroscopy (FTIR).
• X-ray absorption near-edge structure (XANES) spectroscopy and gas chromatography-mass spectrometry (GC-MS).

Main Results:

• Electron irradiation of simple ices produced complex oxygen- and nitrogen-bearing organic molecules.
• FTIR and XANES indicated the presence of alcohols, carboxylic acids, amines, amides, urea, and nitriles.
• XANES analysis revealed highly nitrogen-rich residues (N/C ~ 0.9).

Conclusions:

• Radiation processing of simple ices can generate complex organic molecules relevant to astrobiology.
• The identified molecules, including urea and carboxylic acids, are significant for prebiotic chemistry.
• This study provides insights into the chemical evolution of icy bodies in the outer Solar System.