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Mapping the Thermal Inertia of Phobos using Thermal Infrared Spectra and Thermophysical Modeling

Smith, Nathan Michael (2018) Mapping the Thermal Inertia of Phobos using Thermal Infrared Spectra and Thermophysical Modeling. Masters thesis, Northern Arizona University.

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We present a map of the thermal inertia of Phobos, the larger of Mars' two moons, based on observations collected by Mars Global Surveyor (MGS) using the Thermal Emission Spectrometer (TES) instrument. We compare these observations with an existing airless body thermophysical model that was modified for Phobos. By comparing brightness temperature spectra derived from our TES observations with simulated spectra generated by our thermophysical model, we can constrain the thermal properties of Phobos' surface. One such property, thermal inertia, describes how well a surface resists changes in temperature over time. Thermal inertia is controlled by the physical characteristics of that surface, such as the particle size. Using 10 micron measurements, we derive an average thermal inertia of 42.0 +/- 13.6 J m^-2 K^-1 s^(-1/2) for the observed region, with local variations ranging from ~ 20 - 60 J m^-2 K^-1 s^(-1/2). This is similar to the ~ 50 J m^-2 K^-1 s^(-1/2) thermal inertia of lunar regolith, composed primarily of fine dust. The observations used in this work cover roughly one hemisphere of Phobos, centered on the trailing side of the moon as it orbits around Mars. Our results show a fairly uniform thermal inertia across the observed region, and are generally consistent with prior estimates that relied on disk-integrated observations and not the disk-resolved observations used in this work. We provide a global description of the surface temperature of Phobos as it varies with time, applying our thermophysical model and assuming a uniform thermal inertia of 42 J m^-2 K^-1 s^(-1/2). This provides mission planners with a robust characterization of the thermal environment a spacecraft is likely to experience upon arrival at Phobos' surface.

Item Type: Thesis (Masters)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: Phobos; Mars;
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited: 26 Sep 2018 19:40
URI: http://openknowledge.nau.edu/id/eprint/5290

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