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

1C. Lantz, 2R. Brunetto, 1M.A. Barucci, 1S. Fornasier, 2D. Baklouti, 3J. Bourçois, 3M. Godard
Icarus (in Press) Link to Article [http://dx.doi.org/10.1016/j.icarus.2016.12.019]
1Laboratoire d’Étude Spatiales et d’Instrumentation en Astrophysique (LESIA) – Observatoire de Paris, PSL Research University, CNRS (UMR 8109) / UPMC, Sorbonne Universités / Univ. Paris Diderot, Sorbonne Paris Cité, 92195 Meudon Cedex, France
2Institut d’Astrophysique Spatiale (IAS), UMR 8617 CNRS / Univ. Paris Sud, Univ. Paris-Saclay, Bâtiment 104, 91405 Orsay Cedex, France
3Centre de Sciences Nucléaire et de Sciences de la Matière (CSNSM), UMR 8609 CNRS/IN2P3 – Univ. Paris Sud, Univ. Paris-Saclay, Bâtiment 104, 91405 Orsay Cedex, France
Copyright Elsevier

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 40 keV 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).

One thought on “Ion irradiation of carbonaceous chondrites: a new view of space weathering on primitive asteroids

  1. Pingback: Ion irradiation of carbonaceous chondrites | Prénom Nom

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