Analysis of disk‐resolved OMEGA and CRISM spectral observations of Phobos and Deimos

Abstract

[1] Disk-resolved observations of Phobos acquired by OMEGA at a range of lighting and viewing geometries were fit with the Hapke photometric function to solve for the single particle phase function and single scattering albedos from 0.4 to 2.5 mm. Single scattering albedos were recovered from CRISM observations of Phobos using the OMEGA derived single particle phase function and are similar to those from OMEGA data. Both the ubiquitous red unit and the blue unit around the crater Stickney exhibit a smooth red-sloped spectrum, with a steeper continuum in the redder unit. Single scattering albedos retrieved from CRISM measurements of Deimos are similar to those for the red unit on Phobos. Retrieval of single scattering albedos from OMEGA data at 2.8 to 5.0 mm has greater uncertainty, but results in this wavelength range are also consistent with a smooth, red-sloped spectrum. Phobos' and Deimos' low reflectances, lack of mafic absorption features, and red spectral slopes are incompatible with even highly space weathered chondritic or basaltic compositions. These results, coupled with similarities to laboratory spectra of Tagish Lake (possible D-type asteroid analog) and CM carbonaceous chondrite meteorites, show that Phobos and Deimos have primitive compositions. If the moons formed in situ rather than by capture of primitive bodies, primitive materials must have been added to the Martian system during accretion or a late stage impact.

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

“…Tagish Lake has been suggested as a compositional analog to D‐class asteroids and Phobos based on its low albedo, red slope, and relatively featureless spectrum at VNIR wavelengths (Hiroi et al, ; Lynch et al, ; Murchie & Erard, ; Pajola et al, ; Rivkin et al, ). Of the VNIR spectra measured in this work, that of Tagish Lake (Figure c) is, indeed, the best match to published spectra of Phobos (e.g., Fraeman et al, , ; Murchie & Erard, ; Rivkin et al, ). It has a low albedo, a red slope, and only three very weak spectral features near ~1.9 μm.…”

“…Bidirectional VNIR reflectance spectra of basalt, nontronite, thermally altered nontronite (all both undarkened and darkened), and Tagish Lake fines are displayed in Figure , along with Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra of the Phobos red and blue units simulated to have incidence angles of 30° and emergence angles of 0° (Fraeman et al, ). The <10‐μm basalt sample (Figure a) has a maximum reflectance of 0.268 at 724 nm, with a 1‐μm pyroxene electronic transition band centered at 987 nm and a shallow 2‐μm band centered at 2,120 nm.…”

Application of multiple photometric models to disk-resolved measurements of Mercury’s surface: Insights into Mercury’s regolith characteristics

“…Hapke's model has been used to model a photometric correction to images of many Solar System objects, including the Moon (Sato et al, 2014), Mercury (Domingue et al, 2011(Domingue et al, , 2015, asteroids (Domingue and Hapke, 1989;Helfenstein et al, 1994Helfenstein et al, , 1996Murchie et al, 2002;Lederer et al, 2005Lederer et al, , 2008Hillier et al, 2011;Li et al, 2013;Spjuth et al, 2012;Maoumzadeh et al, 2015), and many planetary satellites (Simonelli and Veverka, 1986;Helfenstein et al, 1988Helfenstein et al, , 1991Domingue et al, 1991Domingue et al, , 1995Skypeck et al, 1991;Domingue and Hapke, 1992;Veverka, 1992, 1994;Hillier et al, 1994;Domingue and Verbiscer, 1997;Simonelli et al, 1998;Hendrix et al, 2005;Verbiscer et al, 2005;Ciarniello et al, 2011;Fraeman et al, 2012). The form of the model used has depended on the state of the development of the model at the time of application, image coverage of the range of plausible i, e, and a values, and coverage of the opposition surge.…”

Advanced concept for a crewed mission to the martian moons

“…When utilizing moon hoppers, science equipment will be designed and mounted in a way that protects it from harsh conditions. Two moon hoppers will be deployed on Phobos to characterize its chemical and mineral composition and structure, with one characterizing spectroscopically blue terrain and the 500 other characterizing spectroscopically red terrain [27]. In addition to ISRU capabilities, their payloads include an alpha particle X-ray spectrometer for chemistry, X-ray diffraction spectrometer for mineralogy, microscopic imager, spectral camera, and a georadar.…”