Reflectance spectroscopy (0.3–2.5 µm) at various scales for bulk-rock identification

We discussed the possibilities and open questions concerning laboratory refl ectance spectroscopy, spectroscopic measurements in the fi eld, hyperspectral image data from spacecraft, and integration of multiscale data. Open questions included: (1) bulk-rock spectral complexity, which provides the geologic basis for every spectroscopic analysis; (2) criteria for laboratory and fi eld spectra classifi cation, as a tool for (3) end-member selection for image data classifi cation; (4) peculiar spectral characteristics of Mount Etna basalts; and (5) effects of remote-sensing data quality. The last three items emerged during a multiscale survey on the Mount Etna volcano. Our laboratory spectroscopic analyses, supported by specifi c petrographic analyses, showed the relationship between absorption-band frequency and spectrally active functional groups and the unexpected effects of bulk-rock composition on this relationship. We studied the muscovite Al-OH band in quartzite and micaschist and Fe 2+ band in pyroxene-bearing cumulates. Laboratory refl ectance spectra of rocks were classifi ed using the concept of spectrofacies. In the case of metamorphic rocks, the result was a tree-structure of rock spectral classes mainly based on the predominant vibrational processes. In the case of basalts, characterized by an overall similarity in their composition, the classes were determined on the basis of overall shape of the spectral curve and on electronic process intensities. Here, we report fi rst results of multiscale data integration for the Mount Etna volcano. Etna rocks consist of basalts, with very low albedo and variable degrees of alteration, and recent lava fl ows are characterized by overall low refl ectance in both ASTER (advanced spaceborne thermal emission and refl ection radiometer) and Hyperion color-composite images. We carried out Spectral Angle Mapper (SAM) classifi cation of Hyperion images, where individual fi eld spectra represented suitable end members for classifi cation of recent lava and pyroclastic deposits. We used fi eld spectra linear combinations to classify mixed pixels and to approximate the classifi cation of altered and oxidized effusive products. Only two laboratory spectral classes coincided with fi eld spectra classes; laboratory spectra were mainly used for spectral features attribution. The overall spectral shape of some of these spectra is still under study. Noise level in Hyperion data precluded the identifi cation of subtle diagnostic iron absorption bands

Accuracy in mineral identification: image spectral and spatial resolutions and mineral spectral properties

Problems related to airborne hyperspectral image data are reviewed and the requirements for data analysis applied to mineralogical (rocks and soils) interpretation are discussed. The variability of mineral spectral features, including absorption position, shape and depth is considered and interpreted as due to chemical composition, grain size effects and mineral association. It is also shown how this variability can be related to well defined geologic processes. The influence of sensor noise and diffuse atmospheric radiance in classification accuracy is also analyzed

Deconvolution of mixtures with high plagioclase content for the remote interpretation of lunar plagioclase-rich regions

Spectroscopic measurements were carried out at Inaf-IAPS Istituto Nazionale di Astrofisica, Roma. EMPA analyses have been performed at Dipartimento di Geoscienze, Padova. E4 end-member has been kindly provided by Dr. Sabrina Ferrari, Department of Geosciences, University of Padova. Financial support by Agenzia Spaziale Italiana, SIMBIO-SYS project. The authors are also grateful to Leah Cheek and to an anonymous reviewer for the stimulating comments and useful suggestions.Anorthositic rocks are widespread on the lunar surface and have probably been formed by flotation of PL over a magma ocean. A large portion of pristine rocks are characterized by a low Mg/(Mg+Fe) ratio, and have been classified as ferroan anorthosite, and recently, after observation from SELENE Spectral Profiler,pure anorthosites regions with more than 98% PL have been recognized. In this paper, we analyze a set of mixtures with PL content similar to the ferroan anorthosites and to the pure anorthosite regions, using the Origin Software and the Modified Gaussian Model. We consider three plagioclases with varying FeOwt% contents (PL1, PL2 and PL3)andthree mafic end-members (1) 100% orthopyroxene, (2) 56% orthopyroxene and 44% clinopyroxene, and (3) 100% olivine (OL). The spectral parameters considered here are: band depth, band center, band width, c0 (the continuum intercept) and c1 (the continuum offset). Here we have shown that in pyroxene (PX)-bearing mixtures, the PX is distinguishable even in mixtures with only 1% PX and that PX band at ca. 900 nm is always deeper than PL1 band while PL2 and PL3 are deeperthan OPX 900 nm band from 95, 96% PL. In OL-bearing mixtures, OL detection limit is 2% when mixed with PL1, and 3% and 4% if mixed with PL2 and PL3. We also demonstrated how spectral parameters vary with PL%, and, generally, increasing the PL content: (1) 1250 nm band depth decreases when mixed with OL, while it deepens in mixtures with PX; (2) 1250 nm band centers generally move towards longer wavelength for PL1-bearing mixtures, while do not show significant variations considering PL2/PL3-mixtures; (3) 1250 nm band width of PL1 in E1 and E5-mixtures substantially widens while in other mixtures it only slightly varies. Here we also proposed an application to a real case, from Proclus crater, revealing how studying terrestrial analogues is fundamental to infer hypothesis on the mineralogical composition of a planetary surface, but also how the spectral convergence of spectra characterized by different compositions can led to misleading interpretations

Atmospheric CO 2 concentrations and δ 13 C values between New Zealand and Antarctica, 1998 to 2010: some puzzling results

From 1998 to 2010, during eight cruises of the M/V Italica between New Zealand and Antarctica, sets of flask air samples were collected and atmospheric CO 2 concentrations were recorded. The δ 13 C of CO 2 from the 1998 to 2003 air samples have already been published and show large interannual variability and an increasing frequency of 13 C-depleted samples. These results were related to a mosaic of areas with positive air–sea fluxes. We report here δ 13 C results from air samples collected from four further cruises. δ 13 C values obtained during the 2004/2005 cruise show an inexplicable saw-toothed distribution. Air samples from the 2005/2006 cruise have δ 13 C values which match previous sets of samples (1998 to 2004) and show more frequent and more negative isotopic events. From 2006 until 2009, further samples could not be collected. However, during December 2009 and January 2010, two more sets of air samples were collected, the δ 13 C values of which greatly differ from previous results, being absolutely homogeneous and paralleled by flat CO 2 concentrations. The results of these last two sets of air samples may be due either to fortuitous environmental conditions or to an improbable and substantial change in oceanic and atmospheric conditions in this section of the circumpolar area. Keywords: New Zealand to Antarctica, flask air samples, atmospheric CO 2 concentrations, carbon isotopic composition of CO 2 , puzzling results (Published: 5 December 2012) Citation: Tellus B 2012, 64 , 17472, http://dx.doi.org/10.3402/tellusb.v64i0.1747

VNIR spectral characteristics of terrestrial igneous effusive rocks: Mineralogical composition and the influence of texture

The authors would like to thank L. Peruzzo for a useful introduction to the use of the SEM at the GeoScience Department of the University of Padua. Financial support was perovided by Agenzia Spaziale Italiana, SIMBIO-SYS project. The authors would also like to thank two anonymous reviewers, and P. K. Byrne and T. Platz, for their helpful suggestions that improved this manuscript.Visible and Near-Infrared (VNIR) reflectance spectroscopy is an important technique with which to map mineralogy and mineralogical variations across planetary surfaces using remotely sensed data. Absorption bands in this spectral range are due to electronic or molecular processes directly related to mineral families or specific compositions. Effusive igneous rocks are widely recognized materials distributed on the surfaces of terrestrial planets, and are formed by primary minerals that can be discriminated by electronic absorptions (e.g. crystal field absorption). In this paper, we review the current knowledge of effusive rock compositions obtained by crystal field absorption in VNIR reflectance spectroscopy, and consider how different petrographical characteristics influence the mineralogical interpretation of such rock compositions. We show that: (1) the dominant mineralogy can be clearly recognized for crystalline material, especially with relatively large crystal dimension groundmass or high porphyritic index; (2) both grain and crystal size are important factors that influence the spectra of effusive rocks where groundmass is generally characterized by microscopic crystals; and (3) glassy dark components in the groundmass reduce or hide the crystal field absorption of mafic minerals or plagioclase otherwise expected to be present

Accuracy in mineral identification: image spectral and spatial resolutions and mineral spectral properties

Problems related to airborne hyperspectral image data are reviewed and the requirements for data analysis applied to mineralogical (rocks and soils) interpretation are discussed. The variability of mineral spectral features, including absorption position, shape and depth is considered and interpreted as due to chemical composition, grain size effects and mineral association. It is also shown how this variability can be related to well defined geologic processes. The influence of sensor noise and diffuse atmospheric radiance in classification accuracy is also analyzed

VNIR spectroscopy of rock forming minerals mixtures: a tool to interpret planetary igneous compositions

Visible and Near Infrared (VNIR) spectroscopy is a powerful technique to investigate and map the mineralogical composition of a Solar System body. Laboratory activities, measuring and analyzing minerals and their mixtures, rock powders and slabs, varying the particle and grain sizes, permit to improve the confidence on the spectra.s interpretation. Here we summarized a set of activity on spectral mixtures between plagioclases and mafic materials at 63-125 and 125-250 µm: illustrating the spectral variations due to the different intensity of the plagioclase absorption varying it Fe2+ content once mixed with orthopyroxene - clinopyroxene, orthopyroxene - olivine poor and - olivine rich materials (Serventi et al., 2013); an IMSA (Hapke, 1993) application to retrieve the endmember.s optical constants and to model the relative mineral abundances in intimate mixtures (Ciarniello et al., 2011) highlighting the influence of the mineral distributions (Carli et al., 2014); a spectra deconvolution with Modified Gaussians (MGM, Sunshine et al., 1990) to define spectral parameters (Band Center, Depth and Width) trends respect to the mineralogical composition of endmembers (mineral chemistry) and mixtures (mineral abundances). Also discussing the influence of the sizes (Serventi et al., 2015)

Una nuova procedura per le correzioni atmosferiche: applicazione sulla Solfatara di Pozzuoli

Il presente lavoro si prefgge di verifcare le potenzialità di una nuova procedura per le correzioni atmosferiche denominata CIRILLO. Inoltre si vuole verifcare la capacità di discriminare le specie mineralogiche che compongono la superfcie della Solfatara di Pozzuoli (Napoli) attraverso dati multispettrali da piattaforma satellitare, confrontandoli con misure iperspettrali eseguite in situ ed in laboratorio. Delle 10 stazioni di misura eseguite in situ viene presa in considerazione quella per la quale sono stati condotti le analisi minero-petrografche del campione prelevato. A tal fne è stato condotto uno studio preliminare sulla composizione minero-petrografca di un campione raccolto su un’unità omogenea di territorio. Il campione è stato sottoposto ad analisi XRF (fuorescenza a raggi-X), XRD (diffrattometria a raggi-X) e chimica presso il Dipartimento di Mineralogia dell’Università di Padova. Le analisi condotte hanno fornito come indicazione la presenza di opale. Lo spettro di questo campione è stato acquisito in rifettanza bidirezionale utilizzando uno spettrometro FieldSpec Pro nel laboratorio di spettroscopia dell’INAF-IASF (Roma) ed a sua volta confrontato con le misure eseguite in condizioni ambientali

Removal of atmospheric features in near infrared spectra by means of principal component analysis and target transformation on Mars: I. Method

Acknowledgments We thank the Italian Institute of Astrophysics INAF for the financial support within the project PRIN-INAF 2011. We are thankful to OMEGA team and ESA staff for scientific, operational and technical supports.The aim of this work is to extract the surface contribution in the martian visible/near-infrared spectra removing the atmospheric components by means of Principal Component Analysis (PCA) and target transformation (TT). The developed technique is suitable for separating spectral components in a data set large enough to enable an effective usage of statistical methods, in support to the more common approaches to remove the gaseous component. In this context, a key role is played by the estimation, from the spectral population, of the covariance matrix that describes the statistical correlation of the signal among different points in the spectrum. As a general rule, the covariance matrix becomes more and more meaningful increasing the size of initial population, justifying therefore the importance of sizable datasets. Data collected by imaging spectrometers, such as the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) instrument on board the ESA mission Mars Express (MEx), are particularly suitable for this purpose since it includes in the same session of observation a large number of spectra with different content of aerosols, gases and mineralogy. The methodology presented in this work has been first validated using a simulated dataset of spectra to evaluate its accuracy. Then, it has been applied to the analysis of OMEGA sessions over Nili Fossae and Mawrth Vallis regions, which have been already widely studied because of the presence of hydrated minerals. These minerals are key components of the surface to investigate the presence of liquid water flowing on the martian surface in the Noachian period. Moreover, since a correction for the atmospheric aerosols (dust) component is also applied to these observations, the present work is able to completely remove the atmospheric contribution from the analysed spectra. Once the surface reflectance, free from atmospheric contributions, has been obtained, the Modified Gaussian Model (MGM) has been applied to spectra showing the hydrated phase. Silicates and iron-bearing hydrated minerals have been identified by means of the electronic transitions of Fe2+ between 0.8 and 1.2 μm, while at longer wavelengths the hydrated mineralogy is identified by overtones of the OH group. Surface reflectance spectra, as derived through the method discussed in this paper, clearly show a lower level of the atmospheric residuals in the 1.9 hydration band, thus resulting in a better match with the MGM deconvolution parameters found for the laboratory spectra of martian hydrated mineral analogues and allowing a deeper investigation of this spectral range. <P /

THE STEREO CAMERA ON THE BEPICOLOMBO ESA/JAXA MISSION: A NOVEL APPROACH

The stereo camera (STC) is one of three channels of the spectrometer and imagers for Mercury Planet Orbiter BepiColombo Integrated Observatory SYStem (SIMBIOSYS), which will be on board the Mercury Planetary Orbiter of the ESA mission BepiColombo. SIMBIOSYS includes also an high resolution imaging channel (HRIC), providing images at spatial resolution of 5m/pixel at the periherm, and the VIS-NIR spectrometer (VIHI) that will provide the global mapping of the Mercury's surface in the spectral range 400-2200 nm, with a spectral sampling of 6.25 nm, and the spatial resolution of 400m/pixel at the periherm. The main scientific objective of STC is the global mapping of the entire surface of the Mercury in 3D and colors with a scale factor of 50m/pixel at the periherm. It will allow to generate the digital terrain model (DTM) of the entire surface improving the interpretation of morphological features at different scales and topographic relationships. The harsh environment of the Mercury will strongly affect the functionalities and performance of the instruments reducing the resources allocated to the payload. Even for the stereo camera, as for most of the instrument on board BepiColombo, a novel design had to be considered. We have implemented an original optical design, modifying a classical configurations, and a new technique of acquiring the stereo pairs for generating the DTM of the surface. The new technique will have an impact on the software chain generating the DTM and on the observation strategy. The stereo camera consists of two channels, looking at the surface at ±20° from the nadir direction, converging on the same bidimensional focal plane assembly, with no mechanical movable parts. The configuration of the focal plane assembly allows to apply the push-frame technique to acquire the stereo images