Small Solar System Bodies as granular media

Hestroffer, Daniel; Sánchez, Paul; Staron, Lydie; Bagatín, Adriano Campo; Eggl, Siegfried; Losert, Wolfgang; Murdoch, Naomi; Opsomer, Eric; Radjaï, Farhang; Richardson, D. C.; Salazar, Michael R.; Scheeres, Daniel J.; Schwartz, S. R.; Taberlet, Nicolas; Yano, Hajime

doi:10.1007/s00159-019-0117-5

Cited by 40 publications

(22 citation statements)

References 323 publications

(395 reference statements)

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“…Beyond the terrestrial gravity that we experience every day-and, in particular, when gravity is weaker-exploration and sampling missions must carefully consider their destination when designing instruments. This holds true for destinations like our Moon (Nash et al 1993) or other planets, where gravity is at least comparable to that of Earth, but also for the extreme case of asteroids, where gravity can be 4-5 orders of magnitude weaker (Hestroffer et al 2019). As examples of the latter microgravity regime, indeed the surfaces of both (101955) Bennu (Barnouin et al 2019) and (162173) Ryugu (Watanabe et al 2019) have been shown to be composed of loosely bound rubble.…”

Section: Introductionmentioning

confidence: 88%

Stick-slip Dynamics in Penetration Experiments on Simulated Regolith

Featherstone¹,

Bullard²,

Emm³

et al. 2021

Planet. Sci. J.

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The surfaces of many planetary bodies, including asteroids and small moons, are covered with dust to pebble-sized regolith held weakly to the surface by gravity and contact forces. Understanding the reaction of regolith to an external perturbation will allow for instruments, including sensors and anchoring mechanisms for use on such surfaces, to implement optimized design principles. We analyze the behavior of a flexible probe inserted into loose regolith simulant as a function of probe speed and ambient gravitational acceleration to explore the relevant dynamics. The EMPANADA experiment (Ejecta-Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids) flew on several parabolic flights. It employs a classic granular physics technique, photoelasticity, to quantify the dynamics of a flexible probe during its insertion into a system of bi-disperse, centimeter-sized model grains. We identify the force chain structure throughout the system during probe insertion at a variety of speeds and for four different levels of gravity: terrestrial, Martian, lunar, and microgravity. We identify discrete, stick-slip failure events that increase in frequency as a function of the gravitational acceleration. In microgravity environments, stick-slip behaviors are negligible, and we find that faster probe insertion can suppress stick-slip behaviors where they are present. We conclude that the mechanical response of regolith on rubble-pile asteroids is likely quite distinct from that found on larger planetary objects, and scaling terrestrial experiments to microgravity conditions may not capture the full physical dynamics.

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Section: Introductionmentioning

confidence: 88%

Stick-slip Dynamics in Penetration Experiments on Simulated Regolith

Featherstone¹,

Bullard²,

Emm³

et al. 2021

Planet. Sci. J.

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“…E. g., an external acceleration that changes the spin rate by more than 0.17 n the time scale of one orbit would probably be sufficient to drive 2006 HY 51 out of the 964:1 spin-orbit resonance. The distribution of main belt asteroid rotation periods is fairly wide and limited on the high end by approximately 2.4 hours (Hestroffer et al 2019) for radii greater than approximately 0.1 km with most of the objects spinning quite fast. The high rates of rotation are commonly attributed to the secular YORP acceleration, which is caused by irregularities in asteroid's shape, solar irradiation of the surface, and thermal radiation from the surface.…”

Section: Mapping Resonances Of 2006 Hy51mentioning

confidence: 98%

Spin-orbit resonances of high-eccentricity asteroids: regular, switching, and jumping

Makarov¹,

Goldin²,

Veras³

2021

Preprint

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Few solar system asteroids and comets are found in high eccentricity orbits (e > 0.9) but in the primordial planetesimal disks and in exoplanet systems around dying stars such objects are believed to be common. For 2006 HY51, the main belt asteroid with the highest known eccentricity 0.9684, we investigate the probable rotational states today using our computer-efficient chaotic process simulation method. Starting with random initial conditions, we find that this asteroid is inevitably captured into stable spin-orbit resonances typically within tens to a hundred Myr. The resonances are confirmed by direct integration of the equation of motion in the vicinity of end-points. Most resonances are located at high spin values above 960 times the mean motion (such as 964:1 or 4169:4), corresponding to rotation periods of a few days. We discover three types of resonance in the high-eccentricity regime: 1) regular circulation with weakly librating aphelion velocities and integer-number spin-orbit commensurabilities; 2) switching resonances of higher order with orientation alternating between aligned (0 or π) and sidewise (π/2) angles at aphelia and perihelia; 3) jumping resonances with aphelion spin alternating between two quantum states in the absence of spin-orbit commensurability. The islands of equilibrium are numerous at high spin rates but small in parameter space area, so that it takes millions of orbits of chaotic wandering to accidentally entrap in one of them. We discuss the implications of this discovery for the origins and destiny of high-eccentricity objects and the prospects of extending this analysis to the full 3D treatment.

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“…Nonetheless, small bodies do not behave like fluids. In effect, being non-monolithic or cohesionless does not mean being fluid, and small bodies are thought to behave more like granular materials that still have certain levels of shear and/or cohesive strengths [175]. By using the limit-analysis approach of plastic theories, Ref.…”

Section: Spin Limitmentioning

confidence: 99%

Shapes, structures, and evolution of small bodies

Yun

Michel

2021

Astrodyn

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Small bodies are among the best tracers of our Solar System's history. A large number of space missions to small bodies (past and future) offer a unique opportunity to use these bodies as a natural laboratory to study the different processes, mechanical structures, and responses that drive the origin and evolution of small bodies, which are connected to the origin, evolution, and current architecture of the Solar System. Images of small bodies sent by spacecraft have revealed unexpectedly rich and complex geological worlds.In addition to very diverse compositions, small bodies in the Solar System have highly diverse shapes and structures, which reflect both different evolutionary paths and material properties. Furthermore, each individual body has diverse geological features on its surface, which include craters of various sizes and depths, boulders of different sizes and morphologies, lineaments, fractures, pits, signatures of landslides, terraces, and ridges. Such a geological richness could not be detected via ground-based observations, and we are still at the beginning of understanding their significance on the low-gravity surfaces on which they manifest. The combination of space mission data and numerical modeling allows us to enrich our understanding of the origin, evolution, and physical properties of these fascinating bodies. For instance, starting from the shape models, bulk densities, and spin rates determined from space mission data, we can investigate the formation mechanisms that lead to the observed properties of small bodies. We can also infer the interior and mechanical properties (e.g., friction and cohesion) that allow a small body to be structurally stable, as well as its further potential evolution under processes such as a spin rate increase or an impact. Then, considering the various processes that these bodies experience during their evolution, we can investigate how these processes modify their properties and, in turn, how those properties influence the outcome of these processes. This paper reviews our current knowledge of small-body shapes and structures and discusses the various processes that are responsible for their formation and evolution, which can modify the characteristics of the bodies. We separately consider each population of small bodies, although in some cases, such as active asteroids and comets, the distinction between two populations solely in terms of physical properties is not clear. We then summarize the main findings regarding the physical properties of small bodies that have been the target of rendezvous or sample return missions.

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Small Solar System Bodies as granular media

Abstract: Small solar system bodies as granular media 3

Cited by 40 publications

References 323 publications

Stick-slip Dynamics in Penetration Experiments on Simulated Regolith

Stick-slip Dynamics in Penetration Experiments on Simulated Regolith

Spin-orbit resonances of high-eccentricity asteroids: regular, switching, and jumping

Shapes, structures, and evolution of small bodies

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