Date of Degree
MS (Master of Science)
Halekas, Jasper S
First Committee Member
Gurnett, Donald A
Second Committee Member
Spangler, Steven R
Since different parts of the Moon display varying magnetic field strengths, our goal was to determine whether these differences are due to specific geological characteristics. We found that older materials tend to be more magnetic than younger materials. Additional statistical studies found that the mare regions of the Moon are less magnetic than the plains and terra regions. We did not find a simple relationship between lunar magnetism and crustal thickness, and this is inconsistent with the hypothesis that thicker crust is more magnetic since there is additional material. Thus, it is not just a matter of the amount of magnetic material that determines the magnetic field strength of the lunar crust. Our results demonstrate that magnetism and crustal thickness have a complex relationship, with multiple distinct groups corresponding to various regions of the Moon. The lunar maria formed a particularly distinct group, consisting of low magnetism and thin crust, while the lunar highlands consist of thick crust but typical magnetic field values.
The ejecta thickness and magnetic field distributions for specific craters showed that larger impact basins have a thicker and more widespread ejecta blanket than smaller craters. We did not find a consistent pattern of magnetic field enhancements near specific craters, but evidence for these strong magnetic signatures was present for Mare Crisium and Mare Nectaris. These results may support the hypothesis that ejecta materials are carriers of magnetism, and this may be the reason for their tendency to have higher magnetic field strengths.
The Moon consists of a wide range of magnetic field strengths. The Moon is also composed of different aged materials and geologic terranes, such as highland regions and lunar maria (the dark patches one sees when looking up at the Moon). Thus, it is plausible that the differences in magnetism may be due to the variations in ages and terranes. Indeed, we found that mare material tends to have the weakest magnetism and that the oldest material is the most strongly magnetic.
The crustal thickness of the Moon also varies, and we hypothesized that thicker crust would display higher magnetic field values since there would be additional magnetic material. However, we discovered a complex relationship with multiple distinct magnetism/crustal thickness groups corresponding to various parts of the Moon. These groups outlined specific lunar regions, including the lunar maria and highlands, when they were plotted on a map.
When an asteroid or other impactor hits the Moon, ejecta material is spewed outwards from the impact. These ejecta materials can maintain their magnetism, so one might expect to find high magnetic field values around large impact basins. However, we did not find clear evidence for these magnetic enhancements.
Geology, Magnetism, Moon, Planetary science
viii, 62 pages
Includes bibliographical references (pages 60-62).
Copyright © 2017 Staci L. Tiedeken
Tiedeken, Staci L.. "Magnetism and geology of the moon." MS (Master of Science) thesis, University of Iowa, 2017.