Laboratory far-infrared spectroscopy of terrestrial sulphides to support analysis of cosmic dust spectra

Abstract

As an aid in interpreting data from space far‐infrared (far‐IR) missions, such as the Herschel Space Observatory with its Photodetector Array Camera and Spectrometer, this paper presents spectroscopic studies of selected naturally occurring terrestrial sulphide minerals in the wavelength range 15–250 μm. The data can also be used to support the return from other, both past and planned, IR space missions, such as the Infrared Space Observatory, Spitzer, SOFIA, SPiCA and Millimetron. In this study, we present far‐IR spectra for 11 natural sulphide minerals in the form of dispersed powders of micron particle dimensions. Samples of various sulphides from the American Museum of Natural History mineral collection were selected based on criteria of diversity and potential astrophysical relevancy, based on their identification in Stardust, in stratospheric interplanetary dust particle samples, or in meteorites. Mineral species include digenite, galena, alabandite, sphalerite, wurtzite, covellite, pyrrhotite, pyrite, marcasite, chalcopyrite and stibnite. Most of the sulphides examined possess prominent and characteristic features in the far‐IR range. Spectra obtained are compared to those available from previous studies. Far‐IR peak frequencies and mass absorption coefficient values are tabulated. Effects of particle size distribution, low temperature, and provenance on IR spectra are demonstrated for selected samples.

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

“…Sulfides are another intriguing possibility that could account for these spectral features. These minerals, which are common in chondritic meteorites, tend to be featureless throughout most of the mid‐IR, with one or more strong features at <500 cm −1 (Brusentsova et al, ). Again, however, none of the phases that have been previously measured display a single sharp peak near ~466 cm −1 , as is seen for Phobos.…”

Lunar ore geology and feasibility of ore mineral detection using a far-IR spectrometer

“…On the other hand, common ore minerals, oxides, and sulfides on the Earth and the Moon (for example, ilmenite, troilite, and pyrite) have distinct absorption bands in the FIR range, between 20 and 40 µm (Figure 6). The same applies to other common sulfides, such as pyrrhotite (Hony et al, 2002) or chalcopyrite (Brusentsova et al, 2012). Notably, the spectral features of the ore minerals mentioned above in the FIR range do not significantly interfere with the rock-forming minerals (Figure 6), in contrast to the currently available NIR range (Figure 5).…”

“…Therefore, the potential presence of mimetite would only increase the chances of finding sulfide mineralization. (Hony et al, 2002;Brusentsova et al, 2012), (B) silicates (Koike et al, 2000;Gielen et al, 2008;Chihara and Koike, 2017), and (C) sulfates (Bishop and Murad, 2005;Bishop et al, 2014;Bhattacharya et al, 2016) measured at room temperature. Literature data for sulfates and silicates are unavailable for <400 cm −1 (>25 µm) and <250 cm −1 (>40 µm), respectively.…”

“…Literature data for sulfates and silicates are unavailable for <400 cm −1 (>25 µm) and <250 cm −1 (>40 µm), respectively. Sulfate mass absorption coefficients were calculated from data on transmittance, sample weight, and active cross-sectional area according to the method presented by Brusentsova et al (2012). The mass absorption coefficient for troilite is normalized (troilite maximum = pyrite maximum) because Hony et al (2002) only report normalized values without specifying normalization factors.…”

Tracing the history of an unusual compound presolar grain from progenitor star to asteroid parent body host

“…Lodders and Fegley (1999) include alabandite as a condensate expected in C stars; however, the Mn-bearing phase predicted for M stars is rhodonite (Mn2SiO4) within olivine (their Table 1). Laboratory IR spectra of alabandite and oldhamite show features near 47.6 µm and 40 µm, respectively (Nuth et al, 1985;Brusentsova et al, 2012). Our identification of alabandite and oldhamite in presolar material is especially interesting because neither phase has been observed in AGB star envelopes in astronomical observational work.…”