Date of Award

Spring 5-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Earth & Planetary Sciences

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

The reflectance properties of a planetary surface are related to the physical and compositional properties of that body. Photometry is a powerful method for determining differences in composition and regolith structure, and photometric data from orbital images coupled with soil sample data can greatly enhance our understanding of the regolith properties of our nearest neighbor, the Moon. At the time of writing, the United States has no operating missions on the Moon and no future plans to send robots or humans to study our nearest neighbor, so we must rely on remote sensing data to provide us with information about the lunar surface. This dissertation uses photometric studies of high-resolution Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) images and Hapke photometric modeling to understand the behavior and composition of lunar soil at spacecraft landing sites and areas of non-mare volcanism on the Moon. This work has implications for future mission planning and implementation, including landing site selection, landing safety, and sampling strategies. Topics include: i) the effects of rocket exhaust on lunar soil reflectance properties at the Apollo, Luna, and Surveyor landing sites, ii) photometric analysis of the recent Chang'e-3 landing site and comparison of reflectance alterations with those of older landing sites, and iii) compositional variations at regions of non-mare volcanism using NAC photometry and spectral analysis of glassy analog materials.

Rocket exhaust from the Apollo, Luna, and Surveyor descent engines disturbed the regolith at their landing sites, causing the soil to become more reflective. These surface alterations, which we call "blast zones", are still evident in NAC images, and I use photometry and Hapke modeling to show that the increase in reflectance was caused by smoothing, destruction of fine-scale surface structure (i.e., "fairy-castle" structure), and possibly redistribution of fine particles. The recent Chinese Chang'e-3 spacecraft also disturbed the soil at its landing site in the same fashion, and I show that the reflectance changes and area of disturbance are in family with those of older landing sites, indicating reflectance changes have not changed on the order of decades. I determine the relationship between lander mass and blast zone area and use this to make predictions of the area of soil disturbance for future missions. Finally, using photometric methods optimized from landing site studies, I place compositional constraints on areas of non-mare and intrusive volcanism and confirm that these areas exhibit a range of evolved silicic compositions (dacite, andesite, and rhyolite) and pyroclastic deposits, and should be considered as scientific targets for future landed sample-return missions.

Language

English (en)

Chair and Committee

Bradley L Jolliff

Committee Members

Raymond Arvidson, Randy L Korotev, William B McKinnon, David A Peters

Comments

Permanent URL: https://doi.org/10.7936/K7PG1PWK

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