Skip to Main content Skip to Navigation
Conference papers

Effects of surface texture and measurement geometry on the near infrared water-of-hydration absorption bands. Implications for the Martian regolith water content

Abstract : Near-IR reflectance spectroscopy is widely used to detect mineral hydration on Solar System surfaces by the observation of absorption bands at 1.9 and 3 µm. Recent studies established empirical relationships between the strength of the 3 µm band and the water content of the studied minerals (Milliken et al., 2005). These results have especially been applied to the OMEGA dataset to derive global maps of the Martian regolith water content (Jouglet et al., 2006 and Milliken et al., 2006). However, parameters such as surface texture and measurement geometry are known to have a strong effect on reflectance spectra but their influence on the hydration bands is poorly documented. The aim of this work is the determination of the quantitative effects of particle size, mixing between materials with different albedo and measurement geometry on the absorption bands at 1.9 and 3 µm. We used both an experimental and a modeling approach to study these effects. Bidirectional reflectance spectra were measured for series of well characterized samples (smectite, volcanic tuff and coals, pure and mixed) and modeled with optical constants of a smectite (Roush, 2005). Criteria commonly used to estimate the strength of the bands were then calculated on these spectra. We show that particle size has a strong effect on the 1.9 and 3 µm bands strength, especially for the finest particles (less than 200 µm). Mixing between a fine smectite powder and anthracite powders with various particle sizes (modeled by a synthetic neutral material) highlights the strong effect of the materials albedo on the hydration band estimation criteria. Measurement geometry has a significant effect on the bands strength for high phase angles. Furthermore, the relative variations of band strength with measurement geometry appear very dependent on the surface texture. We will present in details the relationships between these physical parameters and various criteria chosen to estimate the hydration bands strength. We will then discuss the implications of these results in terms of uncertainties on the quantification of water-of-hydration and in terms of detection limit of mineral hydration through the identification of the 1.9 and 3 µm bands. The discussion will especially focus on the case of Mars and the results of the OMEGA instrument.
Document type :
Conference papers
Complete list of metadatas

https://hal-insu.archives-ouvertes.fr/insu-00358045
Contributor : Béatrice Pibaret-Bourdon <>
Submitted on : Monday, February 2, 2009 - 4:07:30 PM
Last modification on : Friday, September 25, 2020 - 11:20:11 AM

Identifiers

  • HAL Id : insu-00358045, version 1

Collections

INSU | CNRS | OSUG | UGA

Citation

Antoine Pommerol, Bernard Schmitt. Effects of surface texture and measurement geometry on the near infrared water-of-hydration absorption bands. Implications for the Martian regolith water content. European Planetary Science Congress 2006, 2006, Berlin, Germany. ⟨insu-00358045⟩

Share

Metrics

Record views

67