[astro-ph.EP] Aims. The ratio between infrared and visible albedo, pIR/pV, provides a simple proxy for the spectral slope of asteroid surfaces between the visible and near-infrared wavelength ranges. The aim of this work is to assess whether the different spectral units of Phobos occupy the same spectral parameter space as the primitive asteroid populations in order to confirm or not its possible asteroidal origin.
Methods. For each of the three spectral units of Phobos (Red, Transitional and Blue), we extracted averaged, normalised reflectance spectra by comparing normalised reflectance in the visible (0.50-0.60 μm) and near-infrared (3.1-3.8 μm) wavelength ranges from the Mars Express OMEGA instrument, to compute a proxy for the infrared-visible albedo ratio (RP). Then, using the database of visible and infrared albedos compiled in the Minor Planet Physical Properties Catalogue (MP3C), we computed asteroid pIR/pV values (RA), to compare to those for Phobos.
Results. The RP for the Red, Transitional and Blue regions vary between 2.90 and 3.12, 2.32 and 2.35, 1.64 and 1.85 respectively. These values span a range occupied by primitive asteroid populations, with the Transitional and Red regions coinciding with the high ratio regime within the pIR/pV domain, which is commonly associated with red-sloped primitive asteroids, including D- and T-type objects as well as Jupiter Trojans.
Visible geometric albedo, pV, as a function of the infrared-to-visible albedo ratio, RA = pIR/pV, for the selected asteroids, selected on the basis of their spectroscopic classes/complexes compared to the same quantities for the Blue and Red Units of Phobos.– [astro-ph.EP]
T.J. Dyer, J. Beccarelli, M. Delbo, C. Avdellidou, M. Pajola, A. Milton, A. Lucchetti, G. Munaretto
Comments: 9 pages, 3 figures, 1 table, accepted for A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2608.11779 [astro-ph.EP] (or arXiv:2608.11779v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2608.11779
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Submission history
From: Thomas James Dyer
[v1] Wed, 12 Aug 2026 08:21:25 UTC (278 KB)
https://arxiv.org/abs/2608.11779
Astrobiology, Astrochemistry, Astrogeology,
