Phase reddening on near-Earth asteroids: Implications for mineralogical analysis, space weathering and taxonomic classification

2012/04/25 by Juan A. Sanchez, Vishnu Reddy, V. Reddy +7 · 200 citations
Earth and Planetary Sciences · Physics and Astronomy · #Asteroid #Astro and Planetary Science #Astrobiology #Astronomy #Astrophysics #Chondrite #Degree (music) #Geological and Geochemical Analysis #Geology #Materials science #Meteorite #Ordinary chondrite #Phase (matter) #Phase angle (astronomy) #Physics #Planetary Science and Exploration #Space weathering #Spectral line #astro-ph.EP

paper · pdf · doi:10.1016/j.icarus.2012.04.008

published in Icarus 220(1), 36-50 (Elsevier BV) · 36 pages, 15 figures, 4 tables, Accepted for publication in Icarus

openalex publication_date 2012/04/25 · arxiv created 2012/05/01 · arxiv updated 2015/06/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Phase reddening is an effect that produces an increase of the spectral slope and variations in the strength of the absorption bands as the phase angle increases. In order to understand its effect on spectroscopic observations of asteroids, we have analyzed the visible and near-infrared spectra (0.45-2.5 μm) of 12 near-Earth asteroids observed at different phase angles. All these asteroids are classified as either S-complex or Q-type asteroids. In addition, we have acquired laboratory spectra of three different types of ordinary chondrites at phase angles ranging from 13° to 120°. We have found that both asteroid and meteorite spectra show an increase in band depths with increasing phase angle. The spectral slope of the ordinary chondrites spectra shows a significant increase with increasing phase angle for g > 30°. Variations in band centers and band area ratio (BAR) values were also found, however they seems to have no significant impact on the mineralogical analysis. Our study showed that the increase in spectral slope caused by phase reddening is comparable to certain degree of space weathering. In particular, an increase in phase angle in the range of 30° to 120° will produce a reddening of the reflectance spectra equivalent to exposure times of ~ 0.1x10⁶ to 1.3x10⁶ years at about 1 AU from the Sun. Furthermore, we found that under some circumstances phase reddening could lead to an ambiguous taxonomic classification of asteroids.

Citations

• Space weathering and the interpretation of asteroid reflectance spectra
• Spextool: A Spectral Extraction Package for SpeX, a 0.8–5.5 Micron Cross‐Dispersed Spectrograph
• A coordinated spectral, mineralogical, and compositional study of ordinary chondrites
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• Modeling asteroid surfaces from observations and irradiation experiments: The case of 832 Karin
• Mineralogical Variations within the S-Type Asteroid Class
• An extension of the Bus asteroid taxonomy into the near-infrared

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