He + Irradiation of the Murchison Meteorite: Insights Into the Effect of Solar Wind Irradiation on Different Types of Organic Matter

Abstract Organic matter (OM) in C‐type asteroids provides important insights into the early evolution of the solar system and the origin of life on Earth. However, the responses of different types of OM to space weathering remain unclear. Here, we performed a He + irradiation experiment on the Murchison meteorite to simulate the solar wind irradiation process; the experiment was conducted at a fluence of 1.2 × 10 17 ions/cm 2 , simulating the solar wind exposure of a C‐type asteroid over an 800‐year timescale. Raman and nanoscale infrared spectroscopy were used to analyze the changes in OM after He + irradiation. The nano‐IR spectra revealed the presence of six organic functional groups (carboxylic acids, aliphatic and aromatic hydrocarbons, amides, amino acids, and aldehydes) within the macromolecular and soluble OM of the Murchison matrix. Irradiation led to an increase in the disorder of OM and reduction in the total OM content via the disruption of C bonds in macromolecular organic compounds and sputtering of their constituent atoms and molecules. Aliphatic hydrocarbons were modified to the greatest degree while aromatic hydrocarbons were more resistant to He + irradiation. These findings enhance our understanding of the formation and evolution of extraterrestrial OM during the process of solar wind irradiation.