Modelling of spectra with and without dust from Martian surface based on infrared data

transactions of the institute of aviation n0. 4 (245), pp. 287-308, Warsaw 2016 Doi: 10.5604/05096669.1226928 ISSN 0509-6669 eISSN 2300-5408 MoDeLLinG of sPectra With anD Without Dust froM Martian surface BaseD on infrareD Data NatalIa ZaleWSka Space technologies Division, Institute of aviation, al. krakowska 110/114, 02-256 Warsaw, Space Research Centre, Polish academy of Sciences, ul. Bartycka 18a, 00-716 Warsaw, abstract this article aims to show mineral composition of Mars surface based on teS spectra (thermal emission Spectrometer-Mars Global Surveyor), measured in infrared thermal range. It presents how, based on teS data, spectra from selected Martian regions were modelled and interpreted after prior removal of atmospheric influences from the spectra using the Radiative transfer algorithm and Deconvolution algorithm. the spectra from dark area of Cimmeria terra and light Isidis Planitia were elaborated in cited publications. In the case of light areas ex. arsia Mons, spectrum of dusty weathered surface of Mars was obtained (also after removal of atmospheric influences) from averaging spectra of dusty regions of Mars. those aforementioned spectra were used in modelling Martian surface aiming to determine their mineral composition. Deconvolution algorithm was chosen from the mentioned methods as a tool for the modelling. the spectra described above were used for the Martian surface modelling, such as the Hellas Basin and Martian meteorites SNC (Shergottites, Nakhlites, Chassignites), in order to determine their mineral composition. as a modelling tool one of the following methods of deconvolution algorithm can be chosen. Spectra for the modelling were obtained from the PFS spectrometer (Planetary Fourier Spectrometer) - (Mars express) and mineralogical composition of basalts from the southern part of Poland were used for this purpose. the method of modelling which was used to determine the mineral composition of Mars and dust can be used in determining mineral composition of selected areas on the earth from aerial and satellite levels, e.g., soil and vegetation with the use of spectral libraries and spectra of individual plant species. keywords: Mars, deconvolution algorithm, infrared spectrometry, Martian dust, spectra modelling. 1. introDuction Mars infrared spectra indicate that the majority of regions of the planet is composed of basalt, volcanic rock [1]. It is confirmed by studies carried out primarily by Martian Viking landers missions 1, 2 and Mars Pathfinder lander and wheeled robotic Mars rover named Sojourner, which investigated the selected areas directly from the surface of Mars, using the XRFS apparatus (X-Ray Spectrometer Fuorescence) and aPXS (alpha Particle X-Ray Spectrometer),[2],[3], [5]. later research mission 288 NatalIa ZaleWSka was studied by rovers Spirit and Opportunity with aPXS apparatus and mini-teS (thermal emission Spectrometer). With this equipment it was possible to determine the elemental composition of selected areas of Mars (Chryse Planitia and Utopia Planitia, the area of Meridiani Planum and Gusev Crater), and then after conversion to oxides, determine the mineral composition [2], [4],[5], [6]. Slightly later hematite has been discovered at terra Meridiani using the teS apparatus and sulfates on the Valles Marineris and clay minerals on the polar caps, with the OMeGa apparatus (Observatoire pour la Mineralogy, l’eau, les Glaces et l’activité). [7]. last mission of Curiosity rover sent to Gale crater brought the most interesting discovery, where using the CheMin (Chemistry & Mineralogy X-Ray Diffraction), SaM (Sample analysis at Mars) and aPXS apparatus (alpha Particle X-Ray Spectrometer) it confirmed the presence of minerals which indicate the turbulent past of Mars. However, for those studies, data from a small portion of Mars was used, which does not reflect the total global petrological construction of the planet. Fig. 1. elevation map of Mars from MOla apparatus (Mars Orbiter laser altimeter) (Mars Surveyor) with marked areas discussed in the article [NaSa Goddard Spaceflight Center, data from MOla, 1997-2006]. [http://www.lpi.usra.edu/science/treiman/greatdesert/workshop/credits/mola.html] Infrared spectroscopy, among others, is used as a method of structural analysis for the study of minerals and rocks. Infrared absorption is caused by vibrations of functional groups and chemical bonds in the molecule of the test compound. Waves of the infrared range have length similar to the length of chemical bonds. Passing through the sample of the test substance, the radiation vibrates chemical bonds of length corresponding to the wavelength absorbed. It is possible to determine the bonds present in the sample due to the fact that each compound has its own characteristic vibration. the vibrations are quantized, that is, they can take only specific, discrete values. the relationship between the frequency of the absorbed radiation ω and initial – e1 and final – e2 internal energy of the molecule is essential. transitions between the quantized energy states give rise to complex band and linear spectra. Most generally, transitions between energy states of the molecule consist in a simultaneous change of vibrational and rotational electron energy. Near infrared absorption corresponds to changes in energy due to vibrational crossings, resulting from mutual vibrations of individual atoms in the molecule. Rotational energy states associated with the rotation of the molecule MODelING OF SPeCtRa WItH aND WItHOUt DUSt FROM MaRtIaN SURFaCe... 289 is located very close to each other and the transitions between them correspond to far infrared or microwave frequency range. Superposition of those two types of energy gives a certain level called rotation-oscillation level, because it is assumed that, approximately, the energy of each level is equal to the sum of rotational and vibrational energy. the wavelength of absorbed radiation determines the position of absorption band of the molecule in the infrared spectrum. the band corresponding to the longest wavelength band is called primary because it represents the smallest value of the vibrational energy in the molecule. Diatomic molecules have only one fundamental absorption band, however, multiple bands also occur corresponding to the baseband, known as overtones. Group frequencies are vibrations associated with certain elements of structure of the molecule and are determined by movements of the nuclei of atoms during vibrations. the vibrations retain its character as they are related to the presence of the established groups in the molecule and are presented in a relatively fixed wavelengths. Some of the vibrations are only active in the Raman spectrum. In each group of the frequencies, we should be aware of factors which determine the number and position of the absorption bands. those factors are: masses of atoms in a molecule, force constants of bonds between atoms of the molecul (...truncated)