¹H.Chen-Chen,¹S.Pérez-Hoyos,¹A.Sánchez-Lavega,²J.Peralta
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115393]
¹Departamento de Física Aplicada, Escuela de Ingeniería de Bilbao, Universidad del País Vasco (UPV/EHU), Bilbao 48013, Spain
²Departamento de Física Atómica, Molecular y Nuclear, Facultad de Física, University of Sevilla, Spain
Copyright Elsevier

The ubiquitous dust in the Martian environment plays a key role in its weather and climate: it must be taken into account in the interpretation of remote sensing data and observations, and could pose a potential risk to surface equipment and operations. In this study, we use observations retrieved by the Instrument Context Camera (ICC) onboard the InSight lander to evaluate the accumulation of dust on the camera lens and estimate the size of the deposited dust particles. Dust contamination is revealed as mottled pattern image artefacts on ICC observations. These were detected using a template matching blob detection algorithm and modelled with a first-order optical model to simulate their size and optical density as a function of the particle diameter. The results show a deep decay in the first 70 sols (LS = 295–337°, MY34) during which dust particles deposited at landing were mostly removed. The subsequent gradual decrease and stable behaviour in the number of detected particles is only interrupted by accumulation and removal periods around sols 160 (LS ~ 23°, MY35) and 800–1100 (LS = 9–150°, MY36). The estimated particle sizes follow a similar trend, with deposited particles due to wind-driven forces (average diameter < 50 μm) being smaller than the ones deposited by other forces during landing, with particles of up to 220 μm of diameter. The results of this study provide an additional source of information for evaluating aeolian dust processes in Mars, with quantitative results on dust accumulation and removal activity, and may contribute to a better determination of dust entrainment threshold models by constraining susceptible dust particle sizes.

^1,4,5Kereszturi Ákos,^2,4Gyollai Ildikó,^2,4Szabó Máté,^3,4Skultéti Ágnes
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115377]
¹Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Hungary
²Institute of Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungary
³Geographical Institute, Research Centre for Astronomy and Earth Sciences, Hungary
⁴CSFK, MTA Centre of Excellence, Budapest, Konkoly Thege Miklós út 15-17., H-1121, Hungary
⁵European Astrobiology Institute, Strasbourg, France
Copyright Elsevier

Shock metamorphic processes in minerals were observed in the recently fallen Chelyabinsk meteorite and compared with two infrared laboratory methods: DRIFT and ATR based spectral analysis types, attached to a Fourier Transformational Infrared Spectrometer (FTIR). Both of ATR and DRIFT methods have advantages and disadvantages for shock stage identification. However, while the ATR method has wide literature background, the DRIFT method was not used in shock metamorphic research yet, hence this study links ATR spectra with DRIFT spectra to obtain reference for such IR methods in the analysis of shock metamorphism. The results show that shock-based spectral changes could be better followed by the decreasing number of peaks with DRIFT than with ATR data; while the situation is opposite for FWHM values, which better characterizes the shock consequences from ATR data. The DRIFT analyses made from bulk meteorite material. Hence more mineral phases were identified than by separate measurements of ATR. The ATR spectra includes rather major vibration, But with DRIFT the minor bands could be also measured. Hence the other shock indicator, the disappearance of minor bands with increasing shock stage could be better followed by DRIFT. The important shock metamorphic indicator, the FWHM could be identified rather from ATR spectra, as the DRIFT spectra includes small sized peaks, and the FWHM values are near to the spectral resolution of DRIFT spectra. Both of ATR and DRIFT methods show shift of IR bands to higher wavenumber with increasing shock stage. Moreover, the DRIFT method shows the split of some minor bands in case of feldspar and pyroxene due to dimerization of silicate structure.

With increasing shock stage one band disappeared and a new one appeared in case of feldspar DRIFT data, while feldspar did not emerge using ATR observations. In case of olivine the major bands shifted by +2… +5 cm−1 using DRIFT and ATR spectra also. In case of pyroxene one band disappeared and new forbidden bands emerged. These results provide starting points to develop shock estimation using DRIFT method too, what is a much more available at various laboratories. However, it is worth mentioning that DRIFT method usually identifies more mineral phases than ATR because of the difference in spatial resolution.