Spectro-photometry of Phobos simulants I. Detectability of hydrated minerals and organic bands - Archive ouverte HAL
Article Dans Une Revue Icarus Année : 2024

Spectro-photometry of Phobos simulants I. Detectability of hydrated minerals and organic bands

Thomas Gautier

Résumé

Previous Mars Reconnaissance Orbiter and Mars Express observations of Phobos and Deimos, the moons of Mars, have improved our understanding of these small bodies. However, their formation and composition remain poorly constrained. Physical and spectral properties suggest that Phobos may be a weakly thermal-altered captured asteroid but the dynamical properties of the martian system suggest a formation by giant collision similar to the Earth moon. In 2027, the JAXA s MMX mission aims to address these outstanding questions. We undertook measurements with a new simulant called OPPS (Observatory of Paris Phobos Simulant) which closely matches Phobos reflectance spectra from the visible to the mid-infrared wavelength range. The simulant was synthesized using a mixture of olivine, saponite, anthracite, and coal. Since observation geometry strongly influences the photometry and spectra of the light reflected from planetary surfaces, we evaluated the parameters obtained by modeling the phase curves u2013 obtained through laboratory measurements u2013 of two different Phobos simulants (UTPS-TB and OPPS) using Hapke IMSA model. Our results show that the photometric properties of Phobos simulants are not fully consistent with those of carbonaceous chondrites and martian meteorites. We also investigated the detection of volatiles/organic compounds and hydrated minerals, as the presence of such components is expected on Phobos in the hypothesis of a captured primitive asteroid. To investigate their detectability, we examined the variability of the 3.28μm and 3.42μm absorption bands related to aliphatic/aromatic carbon (as a proxy of organic material), as well as the 2.7μm Ou2013H feature in a Phobos laboratory spectroscopic simulant. The results indicate that a significant amount of organic compounds is required for the detection of Cu2013H bands at 3.4μm. The bands at 3.28 and 3.42μm are faint (less than 2%) when ∼3 wt% of organic compounds are present in the simulant and are likely undetectable by the MIRS spectrometer onboard the MMX mission. When the concentration of aliphatic and aromatic compounds is increased to 6 wt%, a positive detection starts to become more plausible using remote sensing infrared spectroscopy. In contrast, the 2.7μm absorption band, due to hydrated minerals, is much deeper and easier to detect than Cu2013H organic features at the same concentration levels. The feature is still clearly detectable even when the simulant contains only 3 vol.% of phyllosilicates, corresponding to 0.7 wt% OH groups. Posing limits on detectability of some possible key components of Phobos surface will be pivotal to prepare and interpret future observations of the MIRS spectrometer as well as TENGOO and OROCHI cameras onboard MMX mission.
Fichier principal
Vignette du fichier
1-s2.0-S0019103524002768-main.pdf (7.41 Mo) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte
Licence

Dates et versions

hal-04671992 , version 1 (16-08-2024)

Licence

Identifiants

Citer

Antonin Wargnier, Thomas Gautier, Alain Doressoundiram, Giovanni Poggiali, Pierre Beck, et al.. Spectro-photometry of Phobos simulants I. Detectability of hydrated minerals and organic bands. Icarus, 2024, 421, pp.116216. ⟨10.1016/j.icarus.2024.116216⟩. ⟨hal-04671992⟩
158 Consultations
33 Téléchargements

Altmetric

Partager

More