¹Filip Košek,¹Adam Culka,²Anastasia Rousaki,^2,3Peter Vandenabeele,¹Jan Jehlička
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114533]
¹Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic
²Raman Spectroscopy Research Group, Department of Chemistry, Ghent University, Krijgslaan 281, S12, 9000 Gent, Belgium
³Archaeometry Research Group, Department of Archaeology, Ghent University, Sint-Pietersnieuwstraat 35, B-9000 Ghent, Belgium
Copyright Elsevier

Organic molecules are currently believed to be abundant in space, but the possible biogenic origin, or the mere existence, on some planetary surfaces, Mars specifically, is a pending question. Reliable methods of detection are required to answer this question unambiguously and Raman spectroscopy has already been suggested for this task years ago. With exploration missions aiming to Mars on the horizon, collecting experience and building databases will have crucial importance investigations of analytical data obtained through Raman instrumentation onboard of rovers in the frame of Mars 2020 and other forthcoming missions. This work focuses on the evaluation of some portable Raman systems coupled to different excitation lasers (532, 785, 1064 nm and a dual laser system with sequentially shifted excitation SSE) for the detection of various organic molecules, with emphasis on non-complicated measure protocol and observation of fluorescence emission when a different wavelength is used. By using a simple statistical approach, we demonstrate a generally good readability of the obtained spectra for most of the investigated organics regardless the excitation sources and instruments used. A varying level of fluorescence emission was encountered, resulting in higher background for the 532 nm and 785 nm instrumentation while 1064 nm and SSE spectrometers provided almost fluorescence-free spectra. These results illustrate how the relatively simple miniaturized Raman spectrometers can provide fast and unambiguous identification of various organic compounds which are of great importance in the current and future planetology and/or exobiology missions.

¹Daniele Fulvio,¹Leonardo Fuks,¹Maron Yaima,¹Cires Perez,¹Tahir Tommaso,¹Del Rosso
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114532]
¹Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marques de São Vicente, 22451- 900 Rio de Janeiro, Brazil
Copyright Elsevier

The term “space weathering” refers to processes that include changes in the physical, chemical, mineralogical, and spectral properties of the surface of asteroids, comets, and some planets and their satellites, such as the bombardment by micrometeorites, solar wind ions, and cosmic rays. In this study, we focus on micrometeorite impacts, which may be the primary contributor to the annual mass flow of material that reaches the surface of such bodies. Studying the processes and effects associated with micrometeorite impacts is fundamental for understanding the evolution of the solar system and its components. From an experimental point of view, it is typically assumed that micrometeorite impacts may be simulated by ns -pulsed lasers and, indeed, many experimental studies have been performed based on such assumption. These studies have the common main goal to understand how micrometeorite impacts may change the physical -chemical and spectral properties of the bombarded surfaces. However, here we perform the first experimental study dedicated to the morphological characterization of the impact craters created by ns -pulsed laser ablation, in order to determine how well ns -pulsed lasers simulate the crater morphology of natural micrometeorite impacts. For this purpose, the laser ablation technique was applied to three different silicates: feldspar, quartz, and jadeite. For each of these minerals, two ablation scenarios have been considered: in air and in water. The craters formed by ns -pulsed laser ablation were characterized, from the morphological point of view, using a profilometer. Using this data we estimated the depth:diameter ratio of each crater. The comparison with literature data shows that the simple craters formed by ns -pulsed laser ablation closely resemble craters formed by natural micrometeorite impacts. In other words, from a morphological point of view, ns -pulsed laser ablation is appropriate for the simulation of micrometeorite impacts. We additionally verified that the value of the depth:diameter ratio does not depend, within errors, on the total number of laser pulses or the repetition frequency, at least within the ranges covered in these experiments: i) between 1 and 1200 laser pulses and ii) between 1 and 10 Hz.