Abstract
Spin rates of minor planets or asteroids are known to have been affected by several agents including but not limited to tidal fly-bys, impacts and solar radiation. Surface processes like landslides occur as a result of such rotational changes. We study the evolution of landslides on top-shaped rubble pile asteroids like 101955 Bennu and 162173 Ryugu, with the underlying core modeled as two solid cones fused back to back. Using a depth averaged avalanche theory applicable to granular flows we solve for axisymmetric landslides occurring at various spin rates and regolith friction. Static regions on the surface corresponding to different spin rates are identified from an equilibrium analysis. We then solve for landslides initiated at different latitudes. It is found that landslides equilibrate at lower latitudes as the spin rate is increased. Beyond a critical spin rate regolith is shed from the equator. This critical spin is higher for a lower value of the semi-apex angle of the cone.
Highlights
In the geophysical context, the length scale of surface flows may match the terrestrial scale of planetary bodies, for example, oceanic flows on the Earth and granular avalanches on rubble-pile asteroids like Bennu [1], Itokawa and Ryugu
Before moving to solve the equations we carry out a preliminary analysis for the behaviour of regolith which is initially stationary with respect to the central body
With an increase in the spin rate the equilibration point (EP) shifts downslope towards the equator
Summary
The length scale of surface flows may match the terrestrial scale of planetary bodies, for example, oceanic flows on the Earth and granular avalanches on rubble-pile asteroids like Bennu [1], Itokawa and Ryugu. The latter involves more complications: new terms in the momentum balance equations, a non-uniform gravity field and an undulating basal topography. It is known that asteroids smaller than the kilometer scale but larger than 150 m have a lower limit to the observed spin period of about 2.1 hours The structure of such asteroids is defined by a solid core with a layer of regolith on the surface [2]. To simplify the analysis we assume that the flow is shallow which allows us to average the governing equations along the depth of the flow
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