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Midinfrared spectra and optical constants of bulk hematite: Comparison with particulate hematite spectra |
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| Authors: | AC Marra MD Lane A Blanco |
| Institution: | a Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, U.O.S. Lecce, Strada Provinciale Lecce-Monteroni Km 1.200, 73100 Lecce, Italy b Planetary Science Institute, 1700 E. Fort Lowell, Suite 106, 85719 Tucson, AZ, USA c Dipartimento di Fisica, Università del Salento, Via per Arnesano, 73100 Lecce, Italy |
| Abstract: | Hematite is an iron oxide that is very important for the study of climatic evolution of Mars. It can occur in three forms: nanophase (dark purple), fine-grained (red) and coarse-grained (gray).In a previous work, we studied the influence of particle size and shape on the infrared spectra (in the wavelength range 6.25-50 μm) of submicron red hematite particles and found that bulk optical constants did not fit the spectra of very fine particles with several classes of models.In the present paper, we derive bulk optical constants of a sample of the same parent material of hematite already used in a previous work in order to determine the particulate optical constants. As a first result we find that, also in this case, bulk and particulate optical constants are different from each other. Furthermore, we show that these bulk optical constants, although derived starting from the same parent material of hematite and used with a model adopting the laboratory measured grain size distribution of the sample, cannot be used to reproduce the spectra of submicron particles. Our results can help the scientific community to appropriately model the contribution of hematite submicron grains to the martian dust for a better understanding of the geologic evolution of the planet. |
| Keywords: | Infrared observations Mars Mineralogy Spectroscopy |
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