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Grain Size Characteristics of Primordial Small Bodies in the Solar System

Gustafsson, Annika Lil (2021) Grain Size Characteristics of Primordial Small Bodies in the Solar System. Doctoral thesis, Northern Arizona University.

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In this dissertation, I present a new approach using near-infrared spectroscopy to characterize and constrain the surface properties of unresolved asteroids. This approach will allow for the characterization of many new objects spanning a wide range of sizes and spin rates which will help shed light on the internal structure and evolution of these bodies. For specific near-Earth objects, this technique will allow for rapid characterization of surface properties for sample return missions and hazard assessment. I present an overview of the instrument commissioning of the near-infrared High Throughput Spectrograph on the 4.3-m Lowell Discovery Telescope, an ideal instrument for rapid characterization of both near-Earth and Main Belt asteroids. This instrument will allow for new observations of small bodies for which we will be able to constrain and characterize their surface properties. I present in detail the implementation of our approach using a new application of Hapke modeling specific to unresolved small bodies and an assessment of its sensitivity and ability to uniquely characterize the surface regolith on these bodies. Using laboratory spectra of ordinary chondrite meteorites, I have run over 600,000 models with a range of free parameters into the Hapke modeling to assess its ability to constrain regolith grain size for these samples. I have found that within a +/-10 range of the mineralogy number and +/-0.1 range of volume fraction, we are able to constrain the Hapke grain sizes consistent with the average physical sieve size of our samples. I also present a disk-integrated application of the model for unresolved asteroid spectra which can be compared to ground truth measurements of regolith properties for Eros and Itokawa, and a disk-integrated photometric phase curve application which can be diagnostic of regolith grain size for unresolved bodies with high quality photometric phase curves, particularly those extending beyond phase angles of 30 degrees. There are many future investigations which we discuss that can be carried out using our implementation of the Hapke model. These investigations will have significant impacts on planetary science and in our understanding of the physical properties of the small body population.

Item Type: Thesis (Doctoral)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: near-infrared spectroscopy; radiative transfer modeling; small bodies; surface properties; asteroids
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > Physics and Astronomy
Date Deposited: 02 Feb 2022 21:38
Last Modified: 02 Feb 2022 21:38
URI: https://openknowledge.nau.edu/id/eprint/5634

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