Irradiation induced mineral changes of NWA10580 meteorite determined by infrared analysis^★

¹ Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
² HUN-REN, Institute for Nuclear Research, Debrecen, Hungary
³ Konkoly Thege Astronomical Institute, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
⁴ CSFK, MTA Centre of Excellence Budapest, Konkoly Thege Miklós út 15-17., 1121 Budapest, Hungary
e-mail: pal.bernadett@csfk.org; kereszturi.akos@csfk.org
⁵ Eotvos Lorand University of Sciences (ELTE), Budapest, Hungary
⁶ Geographical Institute, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
⁷ Department of Systems Innovation, School of Engineering, The University of Tokyo, Tokyo, Japan
⁸ Atomki, Institute of Nuclear Research, 4026 Debrecen, Hungary

Received: 14 July 2023
Accepted: 19 November 2023

Abstract

Context. Identifying minerals on asteroid surfaces is difficult as space weathering modifies the minerals’ infrared spectra. This should be better understood for proper interpretation.

Aims. We simulated the space weathering effects on a meteorite and recorded the alterations of the crystalline structure, such as the change in peak positions and full width at half maximum values.

Methods. We used proton irradiation to simulate the effects of solar wind on a sample of NWA 10580 CO3 chondrite meteorites. After irradiation in three gradually increased steps with 1 keV ion energy, we used infrared microscopic reflectance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to identify and understand the consequences of irradiation.

Results. We find negative peak shifts after the first and second irradiations at pyroxene and feldspar minerals, similarly to the literature, and this shift was attributed to Mg loss. However, after the third irradiation a positive change in values in wavenumber emerged for silicates, which could come from the distortion of SiO₄ tetrahedra, resembling shock deformation. The full width at half maximum values of major bands show a positive (increasing) trend after irradiations in the case of feldspars, using IR reflection measurements. Comparing DRIFTS and reflection infrared data, the peak positions of major mineral bands were at similar wavenumbers, but differences can be observed in minor bands.

Conclusions. We measured the spectral changes of meteorite minerals after high doses of proton irradiation for several minerals. We show the first of these measurements for feldspars; previous works only presented pyroxene, olivine, and phyllosilicates.