Space weathering processes such as micrometeorite bombardment and solar wind irradiation alter the microstructural, compositional, and optical properties of airless body regoliths. As a result, space weathering complicates the interpretation of remote sensing data from spacecraft missions [1] . Unlike the Moon and asteroids similar in composition to unaltered ordinary chondrites, very little is known about space weathering of hydrated, organic-rich (carbonaceous or C-type) planetary bodies. In

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... he next three years, the Hayabusa2 and OSIRIS-REx missions will return samples from C-type asteroids Ryugu and Bennu, respectively [2, 3] . To maximize the scientific return of these missions, we simulated solar wind irradiation in the laboratory on CM2 Murchison-a suitable analog for C-type asteroids [4] . We present results from a coordinated analysis investigating how 1 keV/amu H + and He + ion irradiation modifies the physical, chemical, and spectral properties of the organic and inorganic components of carbonaceous chondrites. H + and He + irradiations were performed separately under ultra-high vacuum on two discrete 6x6 mm regions of a dry-cut Murchison slice. Using a flux of 1.1x10 13 ions/cm 2 /s, the first region was irradiated with 4 keV He + to a total fluence of 1.1x10 18 ions/cm 2 (~6000 years of exposure at Bennu) while the second region was irradiated with 1 keV H + to a total fluence of 8.1x10 17 ions/cm 2 (~200 years of exposure at Bennu). To comprehensively analyze the samples, we employed four analytical techniques: (1) X-ray photoelectron spectroscopy (XPS), (2) visible to near infrared (VNIR; 0.35-2.50 µm) spectroscopy, (3) two-step laser-desorption mass spectrometry (μL 2 MS), and transmission electron microscopy (TEM). We observed changes in surface chemistry via in situ XPS using a PHI Versaprobe with a monochromatic, scanning X-ray source (AlKα: 1486.7 eV) and hemispherical electron-energy analyzer. We collected VNIR spectra using a fiber-optic ASD FieldSpec 3 Spectrometer (Malvern Panalytical) under ambient laboratory conditions to understand trends in reflectance. Changes in organic functional group chemistry were evaluated using a 118 nm photoionization spectral map acquired with a µL 2 MS instrument. Using an FEI Quanta 3D focused ion beam scanning electron microscope (FIB-SEM), we prepared eight electron transparent thin sections consisting of matrix material, pyroxene, Mgrich olivine, and Fe-rich olivine from both the H + -and He + -irradiated regions. TEM analysis of these FIB-sections revealed microstructural and chemical changes driven by ion irradiation. Specifically, we acquired bright field (BF), high-angle annular dark field (HAADF), and high-resolution TEM (HRTEM) images, as well as elemental distribution maps, using a JEOL 2500SE 200 kV field-emission scanning