Most small asteroids are defined as "rubble-piles," or bodies with zero tensile strength and large bulk porosity that are tenuously held together by cohesive forces. Improving the accuracy of predictions of asteroid strengths requires suitable laboratory measurements of relevant materials, as well as increasing the availability of materials from sample return. In this work, we use Atomic Force Microscopy (AFM) force measurements and particle characterization to characterize, evaluate, and decouple variables that affect cohesive forces that act between micron-sized grains. In our first investigation we explored interactions of JSC-1 lunar simulant grains using three sample sizes, three spherical AFM tip diameters, and varying relative humidity, observing that the results are very dependent on the RH and, by proxy, adsorbed water. We observed weaker adhesion with larger grain/tip size, which can be attributed to the changing contact area between the samples and the tips. We next performed experiments in vacuum conditions and characterized the cohesive values of a high-fidelity CI simulant (Exolith) based on the CI1 meteorite Orgueil. Our results show no significant trend in adhesion, but we do observe that some correlating characteristics of the grains, such as roughness, can dominate the work of adhesion. The chemical nature of the grains, including their affinity for water, also played a role in if they became more adhesive in vacuum conditions or less adhesive in vacuum conditions. Our studies decouple several factors that contribute to the complex physics of adhesion and even more complex idea of understanding adhesion in a space environment with irregularly shaped grains. This approach will pave the way to a better understanding of regolith surface properties, improve contact models for irregularly shaped particles, and provide suitable inputs for models of asteroid cohesion. This analysis technique can be used on future materials provided by sample return missions.


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Graduation Date





Dove, Adrienne


Doctor of Philosophy (Ph.D.)


College of Sciences



Degree Program

Physics; Planetary Sciences


CFE0009884; DP0028417





Release Date

February 2025

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Campus-only Access)

Restricted to the UCF community until February 2025; it will then be open access.