Coordinated bulk, micro- and nano-scale analyses of experimentally space weathered olivine single crystals
Abstract
Space weathering is a process that affects every airless body in the Solar System. The combined effects of micrometeoroid and high energy particle impacts, solar wind implantation and sputtering, and comminution, lead to chemical and physical changes in airless body regolith surfaces that result in pronounced changes to spectra across multiple wavelength ranges. At visible/near-IR (VNIR) wavelengths, spectra become darker and redder, with weakened crystal field bands. At mid-IR wavelengths, Reststrahlen and transparency features become weaker and the Christiansen feature (CF) emissivity maximum shifts to longer wavelengths.
The relative roles of solar wind and micrometeoroid bombardment in the space weathering process are the subject of much debate. In this work, we subjected single crystals of olivine to simulated solar wind irradiation and micrometeoroid impacts and conducted a set of correlated analyses of the post-impact samples. Polished single crystals of San Carlos olivine were prepared for impact experiments. Prior to the impact experiments, we irradiated one crystal with 12 keV protons to simulate solar wind bombardment. Samples were then subjected to 10,000 impacts by 0.1 μm dust grains traveling at velocities between 1 and 10 km/s. The recovered samples were analyzed using VNIR reflectance spectroscopy, confocal Raman spectroscopy, grazing angle synchrotron X-ray absorption spectroscopy, transmission electron microscopy (TEM) and synchrotron micro- and nano-FTIR reflectance spectroscopy. Raman and IR maps of the impacted samples reveal the presence of amorphous or disordered material around the impact sites. Micro-FTIR spectra reveal disorder through the weakening of the 920 cm-1 Si-O vibrational band in the regions surrounding individual impact craters. Raman spectra in heavily impacted areas of the samples display weaker olivine spectral features and high fluorescence, which is also consistent with the presence of amorphous material. TEM images and electron diffraction patterns indicate the presence of an amorphous rim near a micro-crater. Dark, nano-scale blebs, similar to nano-phase Fe particle found in space natural weathered samples are also observed, although their composition remains to be determined.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P51D2914G
- Keywords:
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- 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5422 Ices;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5470 Surface materials and properties;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS