Temperature is the dominant control of ice stability on the Moon. In order to examine the spatial, quantitative, and temporal variability of lunar ice, in this study I develop components of a ...comprehensive thermal-diffusion model of ice migration. The lunar environment varies dramatically in temperature, from roughly 400 K at the equator, to as low as 20 K in shadowed polar regions. As the sublimation of water ice is exponentially dependent on temperature, this causes an even larger variation in ice stability. However, the lunar thermal environment is a dynamic system. In this work, I model orbital interactions with the Earth and Sun that brought about huge changes in lunar polar illumination. The most dramatic event in this orbital evolution was a high obliquity spin-orbit transition, during which surface temperatures of currently shadowed regions would have exceeded 390 K. Therefore, all lunar ice should have deposited after this event. In order to examine the effects of the evolution of the lunar orbit on the subsurface temperatures and ice migration, I also examine variations in thermal properties and global variation in geothermal heat production. Both of these quantities are important controls over the depth at which ice could be emplaced and are examined here using Apollo era and recent data from the Lunar Reconnaissance Orbiter's Diviner Lunar Radiometer. Additionally, using laboratory data taken under Martian conditions, I examine the likely effects of diffusively emplaced ice on regolith thermal properties. The geometry of vapor-emplaced ice results in a linear variation in thermal conductivity with ice content which differs from previous theory. These components are then compiled together in a preliminary thermal-diffusion model, which will allow for examination of spatial and quantitative prediction of subsurface ice. This model shows that retention of supplied ice is highly temperature dependent, favoring efficient migration of ice into the subsurface between roughly 95 and 145 K, depending on local temperature amplitudes. This causes a favored period in the evolution of the lunar orbit for ice deposition at a given location. Therefore, variations in the spatial distribution of polar volatiles may mark a specific period of enhanced supply, most likely in the form of cometary impacts. I briefly examine how this might play a role in volatile deposition and loss on other solar system bodies.
The Bucksbaum Institute for Clinical Excellence at the University of Chicago was established in 2011 with the mission to improve patient care, strengthen the doctor-patient relationship, enhance ...communication and decision making in health care, and reduce health care disparities. The Bucksbaum Institute supports the development and activities of medical students, junior faculty, and senior clinicians who devote themselves to improving doctor-patient communication and clinical decision making. The institute seeks to enhance the skills of physicians as advisers, counselors, and navigators to help patients make informed decisions when facing complex treatment choices. To achieve its mission, the institute recognizes and supports the activities of physicians who excel in clinical care, supports an array of educational programs, and funds research into the doctor-patient relationship. As the Bucksbaum Institute enters a second decade, its focus will begin to extend beyond the University of Chicago, leveraging alumni and other relationships to improve patient care everywhere.
The heat flow and physical properties package (HP$^3$) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was ...designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0-5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03 to 0.37 m depth range was performed. Using the HP$^3$ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 $\pm$ 0.002 W m$^{-1}$ K$^{-1}$, consistent with the results of orbital and in-situ thermal inertia measurements. This low thermal conductivity implies that 85 to 95\% of all particles are smaller than 104-173 $\mu$m and suggests that any cement contributing to soil cohesion cannot significantly increase grain-to-grain contact areas by forming cementing necks, but could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are 1211$_{-113}^{+149}$ kg m$^{-3}$, indicating soil porosities of 61 \%.
We use the surface temperature response to Phobos transits as observed by a radiometer on board of the InSight lander to constrain the thermal properties of the uppermost layer of regolith. Modeled ...transit lightcurves validated by solar panel current measurements are used to modify the boundary conditions of a 1D heat conduction model. We test several model parameter sets, varying the thickness and thermal conductivity of the top layer to explore the range of parameters that match the observed temperature response within its uncertainty both during the eclipse as well as the full diurnal cycle. The measurements indicate a thermal inertia of 103+48-24 Jm-2K-1s-1/2 in the uppermost layer of 0.2 to 4 mm, significantly smaller than the thermal inertia of 200 Jm-2K-1s-1/2 derived from the diurnal temperature curve. This could be explained by larger particles, higher density, or a very small amount of cementation in the lower layers.
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