Description
- Abstract:
- The modern surfaces of planetary bodies throughout the solar system are shaped by their ancient thermal and interior evolution. Here we work to understand the magnetic and thermal evolutions of two bodies in particular: the Moon and asteroid 16 Psyche. For the Moon, analysis of Apollo samples suggest that an ancient core dynamo produced magnetic field strengths on the same order of magnitude as the Earth’s present day magnetic field and may have had a large degree of variability. To explain both the variability and unexpectedly high magnetic field intensities of the early lunar paleomagnetic record, we investigated a new mechanism to enhance an ancient lunar dynamo. We found that fragments of impactor cores which reach the lunar core-mantle boundary at temperatures below that of the lunar core can theoretically produce enhanced magnetic fields for as long as thousands of years. Therefore, this mechanism should be considered along with other intermittently high intensity lunar dynamo processes. For the asteroid 16 Psyche, the conflicting observations of a metal rich surface and a bulk density of only about half that of iron has resulted in a largely unknown internal structure. Through one-dimensional thermal models of Psyche coupled with viscous removal of pore space, we have determined that a porous iron structure for Psyche is unlikely. Additionally, we have made predictions for the extent of radial contraction and moment of inertia values of Psyche under the assumption that Psyche’s low density is due to a two-layer internal structure composed of a rocky layer above an iron-sulfur core. We determined that estimates of radial contraction from thrust faults, if they are observed, should be able to constrain the thickness of an outer rocky layer and the measurement of the moment of inertia should be able to determine the direction of core solidification. These projects, both as individual works and together as a dissertation, demonstrate the power of using scaling laws and one-dimensional thermal models to understand the early history of solar system objects.
- Notes:
- Thesis (Ph. D.)--Brown University, 2024
Citation
Nichols-Fleming, Fiona,
"Geophysical Evolution of the Moon and Asteroid 16 Psyche"
(2024).
Earth, Environmental and Planetary Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:vk58neyg/
Relations
Collection:
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Earth, Environmental and Planetary Sciences Theses and Dissertations
Theses and Dissertations for the Earth, Environmental and Planetary Sciences department....