Date of Award

January 2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Space Studies

First Advisor

Michael J. Gaffey

Abstract

Recent research suggests that ion bombardment is more effective than micrometeoroid bombardment in albedo darkening of mature lunar soils, whereas micrometeoroid bombardment may act on longer timescales and is more effective in modifying the spectral features of a surface. This, in turn, may be extrapolated to suggest the following: 1) Increased intensities of ion bombardment would correlate negatively with the surface reflectivity of airless, silicate-bearing bodies known to express lunar-style space weathering, such as S-type asteroids, and 2) beyond that of sputtering and ion implantation, there is a gradient of potential interactions between the two weathering processes that may be relevant to space weathering at large, where via the processes of mineral metamictization and structural weakening, ion bombardment may act as a necessary precursor to micrometeroid bombardment in lunar-style space weathering. Because heliosphere research (i.e., the Ulysses spacecraft) reveals that the speed of solar wind rises with solar latitude from the equatorial plane to the poles, the possibility of a correlation is suggested between the albedo of a given S-type asteroid surface and its orbital inclination. In other words, more highly-inclined asteroids would be exposed to higher-intensity solar ion bombardment, which would thereby result in darker (or more quickly darkened) mature surfaces. This proposition is explored via the statistical analysis of a sample group of S-complex airless bodies, resulting in a statistically-significant negative correlation between orbital inclination and albedo at the 75% confidence level. An overall space-weathering scheme is proposed, and implications for space weathering mechanisms as they relate to orbital parameters are discussed.

Download

Share

COinS