Goethite as an alternative origin for the 3.1 µm band on dark asteroids.

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Reference: Beck P., Quirico E., Sevestre D., Montes-Hernandez G., Pommerol A., Schmitt B. (2011). Goethite as an alternative origin for the 3.1 µm band on dark asteroids.. Astron. Astrophys., 526, A85.

Names

Title: Goethite as an alternative origin for the 3.1 µm band on dark asteroids.
Abstract: Context. The reflectance spectra of some main-belt asteroids contain a 3-μm band, which is explained by the presence of water or hydroxyl groups in minerals. Recent observations of 24-Themis have been found to display evidence of water ice.Aims: We synthesize iron oxy-hydroxide materials and in the laboratory measure their near-infrared spectra under dry conditions to compare with asteroid observations.Methods: The syntheses are performed using either the well-established titration method or a non-conventional hydrothermal method. Bi-directional near-infrared reflectance spectra are obtained using the spectrogonio radiometer available at LPG/IPAG. Spectra are measured in a vacuum to avoid contamination by adsorbed water.Results: The reflectance spectra that we measure for synthesized goethite are consistent with published transmission spectra. The 3-μm band in goethite has a minimum around 3.10 μm, similar to observations of 24-Themis. Its overall shape matches well Themis's 3-μm band; goethite-like oxy-hydroxydes are a viable alternative way of explaining 24-Themis near-IR spectra
Keywords: spectroscopy, spectro-gonio radiometer, bidirectional reflection, bidirectional reflectance spectra, band position, near-IR, goethite, meteorite Millbillillie, meteorite Dhofar 700, asteroids
Content: sample, material-matter, spectral data, spectral data use, planetary sciences

Doi

10.1051/0004-6361/201015851

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