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- Title
Moment of Inertia and Tectonic Record of Asteroid 16 Psyche May Reveal Interior Structure and Core Solidification Processes.
- Authors
Nichols‐Fleming, Fiona; Evans, Alexander J.; Johnson, Brandon C.; Sori, Michael M.
- Abstract
The thermal and chemical evolution of (16) Psyche would have been influenced by the direction of core solidification and thickness of an outer (rocky) silicate layer. We model the thermal evolution and core solidification of Psyche for a range of outer silicate layer thicknesses and core sulfur contents to calculate the resulting radial contraction and moments of inertia. We generally find that increasing the thickness of the outer silicate layer by 10 km results in a ∼1‐km reduction in total radial contraction. Additionally, we find that the timing of full core solidification, and thus a large amount of predicted contraction, can differ by up to 25 Myr for inward versus outward core growth. Finally, our calculated moment‐of‐inertia factors for models with inward core growth that contain sulfur are consistently larger than those with outward core growth. Ultimately, spacecraft‐derived estimates of Psyche's moment of inertia and surface contraction will be able to provide constraints on Psyche's interior evolution, silicate layer thickness, and direction of core solidification. Plain Language Summary: The asteroid Psyche has a metal‐rich surface but a lower density than pure metal. This means it may have a significant rocky component in addition to the metal. For the possible scenario in which Psyche is a differentiated body with a silicate rocky layer above an iron‐rich core, we model the temperature evolution for different amounts of rock and different core compositions. When a rocky or metal planetary body cools, it shrinks, which can result in a particular type of tectonic feature called thrust faults. We expect the differences in internal structure and the way in which the core freezes in our models to produce differences in the surface record of faults as well as in the distribution of mass within Psyche. We calculate the predicted decrease in radius and distribution of mass from each of our models and find that the surface record of faulting and the moment of inertia of Psyche are noticeably different depending on Psyche's silicate fraction and internal evolution. If Psyche is indeed a differentiated body, these features will be observed and measured when the dedicated NASA mission to Psyche arrives in 2029. Key Points: Psyche's interior evolution, including core solidification direction, can be inferred from thrust faults and moment of inertia measurementsEstimates of the total radial contraction on Psyche will provide an independent constraint on the thickness of the outer silicate layerA lack of observed thrust faults could suggest that Psyche has a porous iron composition, a young surface age, or both
- Subjects
MOMENTS of inertia; METALS in the body; SOLIDIFICATION; THRUST; SILICATES; IRON
- Publication
Journal of Geophysical Research. Planets, 2024, Vol 129, Issue 7, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2024JE008291