Among the materials of planetological interest, olivine is particularly important due to its ubiquity in the Solar System and to the fact that, in presence of water, it readily alters to iddingsite and various phyllosilicates [1]. Olivine has already been detected on the Martian surface [2], but so far it has not been possible to understand if this olivine shows the typical features of water alteration. One complication is that olivine (or phyllosilicates) is always mixed with pyroxenes and, since pyroxenes and olivine have a similar spectrum in the visible and near infrared, it is difficult to map the real spatial distribution of these two minerals on the Martian surface. For this reason, laboratory studies on olivine and pyroxene samples play an important role in understanding the best way to individuate these two minerals, using their spectral signatures in the visible and near infrared range. In this work we present the results of spectroscopic studies on different particulate samples of various olivines and pyroxenes, analysed in reflectance in the range 0.2-2.5 ìm. Our goal is to study the influence of the grain size on the spectra and, in particular, on the characteristics of the band at about 0.64 ìm, which is commonly present in the spectra of olivine (altered and unaltered) and pyroxene. The same band at about 0.64 ìm, with its two nearest reflectance maxima has been observed in several reflectance spectra of asteroids, as well as in some Martian spectra. In these cases the exact position of the two reflectance maxima, as well as their relative intensity, can supply important information about the characteristics of the regolith present on the celestial object under study. For this purpose, we analysed some reflectance spectra collected by the visible-infrared imaging spectrometer OMEGA/MEX in two regions of Mars where previous works [3,4] reported the presence of olivine deposits: Nili Fossae, part of Isidis Basin and Syrtis Major (15-30°N, 65-80°E) and a portion of Valles Marines around Aurorae Planum and Ganges Chasma (0-15°N, 45-60°W). Our goal is detecting the weak 0.64 ìm feature in OMEGA spectra and comparing it with laboratory spectra, in order to obtain information about the grain size and other characteristics of the Martian regolith
Laboratory spectral measurements of particulate samples of pyroxenes and altered olivine and related planetological studies
M Conte;
2012
Abstract
Among the materials of planetological interest, olivine is particularly important due to its ubiquity in the Solar System and to the fact that, in presence of water, it readily alters to iddingsite and various phyllosilicates [1]. Olivine has already been detected on the Martian surface [2], but so far it has not been possible to understand if this olivine shows the typical features of water alteration. One complication is that olivine (or phyllosilicates) is always mixed with pyroxenes and, since pyroxenes and olivine have a similar spectrum in the visible and near infrared, it is difficult to map the real spatial distribution of these two minerals on the Martian surface. For this reason, laboratory studies on olivine and pyroxene samples play an important role in understanding the best way to individuate these two minerals, using their spectral signatures in the visible and near infrared range. In this work we present the results of spectroscopic studies on different particulate samples of various olivines and pyroxenes, analysed in reflectance in the range 0.2-2.5 ìm. Our goal is to study the influence of the grain size on the spectra and, in particular, on the characteristics of the band at about 0.64 ìm, which is commonly present in the spectra of olivine (altered and unaltered) and pyroxene. The same band at about 0.64 ìm, with its two nearest reflectance maxima has been observed in several reflectance spectra of asteroids, as well as in some Martian spectra. In these cases the exact position of the two reflectance maxima, as well as their relative intensity, can supply important information about the characteristics of the regolith present on the celestial object under study. For this purpose, we analysed some reflectance spectra collected by the visible-infrared imaging spectrometer OMEGA/MEX in two regions of Mars where previous works [3,4] reported the presence of olivine deposits: Nili Fossae, part of Isidis Basin and Syrtis Major (15-30°N, 65-80°E) and a portion of Valles Marines around Aurorae Planum and Ganges Chasma (0-15°N, 45-60°W). Our goal is detecting the weak 0.64 ìm feature in OMEGA spectra and comparing it with laboratory spectra, in order to obtain information about the grain size and other characteristics of the Martian regolithI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
