Ion irradiation of carbonaceous chondrites: A new view of space weathering on primitive asteroids

• Published in: Icarus
• Main Authors: Lantz, C., Brunetto, R., Barucci, M., Fornasier, S., Baklouti, D., Bourçois, J., Godard, M.
• Other Authors: Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Spectroscopy; Meteorites; Asteroids; Surfaces; Experimental techniques; [PHYS]Physics [physics]; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Frontier Mountain; Tagish; Tagish Lake
• Online Access: https://hal.sorbonne-universite.fr/hal-01427337; https://hal.sorbonne-universite.fr/hal-01427337/document; https://hal.sorbonne-universite.fr/hal-01427337/file/Lantz_Ion_irradiation_of.pdf; https://doi.org/10.1016/j.icarus.2016.12.019

International audience We present an experimental study on ion irradiation of carbonaceous chondrites, simulating solar wind irradiation on primitive asteroids, to better constrain the space weathering processes of low albedo objects. The irradiations were performed on pressed pellets of the CV Allende, CO Frontier Mountain 95002 and Lancé, CM Mighei, CI Alais, and ungrouped Tagish Lake meteorites, as well as on some silicate samples (olivine and diopside). We used 40keV He+He+ with fluences up to 6 × 1016 ions/cm2 corresponding to timescales of 103–104 years for an object in the Main Belt. Reflectance spectra were acquired ex situ before and after irradiations in the visible to mid-infrared range (0.4–16 µm). Several spectral modifications are observed. In the MIR range, we observe a shift of the phyllosilicates (near 3 and 10 µm) and silicates (near 10 µm) bands toward longer wavelength. In the visible-NIR range, spectral darkening and reddening are observed for some samples, while others show spectral brightening and blueing. Results are also compared with previous irradiation on ordinary and carbonaceous chondrites. We find that the spectral modifications in the visible range are correlated with the initial albedo/composition. We propose a model for space weathering effects on low albedo objects, showing that those with initial albedo between 5 and 9% shall not suffer SpWe effects in the visible range. These experiments provide new clues on spectroscopic features modifications within the visible-infrared ranges that could be detected in situ by future sample return missions (Hayabusa-2/JAXA and OSIRIS-REx/NASA).