Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

Scheeres, Daniel J.; French, A. S.; Tricarico, P.; Chesley, S. R.; Takahashi, Yasuhiro; Farnocchia, Davide; McMahon, Jay W.; Brack, D. N.; Davis, A. B.; Ballouz, Ronald-Louis; Jawin, E. R.; Rozitis, B.; Emery, Joshua P.; Ryan, A. J.; Park, R. S.; Rush, Brian; Mastrodemos, N.; Kennedy, B. M.; Bellerose, Julie; Lubey, Daniel P.; Velez, D.; Vaughan, Andrew T M; Leonard, Jason M.; Geeraert, J.; Page, Brian R.; Antreasian, P. G.; Mazarico, E.; Getzandanner, K.; Rowlands, D. D.; Moreau, Michael C.; Small, Jeffrey L.; Highsmith, D. E.; Goossens, Sander; Palmer, E. E.; Weirich, J. R.; Gaskell, R. W.; Barnouin, O. S.; Daly, M. G.; Seabrook, J. A.; Asad, M. M. Al; Philpott, L.; Johnson, C. L.; Hartzell, C. M.; Hamilton, Victoria E.; Michel, Patrick; Walsh, K. J.; Nolan, M. C.; Лауретта, Д. С.

doi:10.1126/sciadv.abc3350

Cited by 61 publications

(43 citation statements)

References 67 publications

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“…The above scenario contains an underdense core and equator, where the smaller rubble and void spaces are most prevalent. In that regard, it is consistent with the gravity field of Bennu, which points to a heterogeneous mass distribution (Scheeres et al, 2020).…”

Section: Internal Propertiessupporting

confidence: 80%

“…It is a rubble pile asteroid as well (Fujiwara et al, 2006), but, as shown in Figure 3, requires nearly 15° of internal friction to maintain this rotational state and shape. The variable densities of the two lobes (Kanamaru et al, 2019) may indicate the presence of some larger fragments in the interior that have inherent strength, consistent with findings for Bennu (Daly et al, 2020;Scheeres et al, 2020). 13…”

Section: Equilibrium Figuressupporting

confidence: 76%

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Rotational states and shapes of Ryugu and Bennu: Implications for interior structure and strength

Roberts

Barnouin

Daly

et al. 2021

Planetary and Space Science

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Section: Internal Propertiessupporting

confidence: 80%

Section: Equilibrium Figuressupporting

confidence: 76%

Rotational states and shapes of Ryugu and Bennu: Implications for interior structure and strength

Roberts

Barnouin

Daly

et al. 2021

Planetary and Space Science

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“…We anticipate that a surface layer may have higher porosity, as is observed on Bennu (Barnouin et al 2019). Note that this asteroid's interior is also less dense, which possibly resulted from inelastic deformation (Scheeres et al 2020). The dynamical model assumed the ejected particles to be spherical; however, in reality, this is not the case, and their irregular shapes might induce complex nongravitational forces (Tsuchiyama et al 2011).…”

Section: Discussionmentioning

confidence: 75%

Active Main-belt Asteroid (6478) Gault: Constraint on Its Cohesive Strength and the Fate of Ejected Particles in the Solar System

Nakano¹,

Kim²,

Hirabayashi³

2022

Planet. Sci. J.

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Active asteroid (6478) Gault sheds mass independent of location along its orbit. Rotational instability is considered to induce the observed activities. If this is the case, because Gault’s breakup event has not been detected, surface failure is likely, implying that its surface materials are constantly ejected while its major body remains intact. Given this scenario, we first constrain Gault’s bulk cohesive strength. We then characterize heliocentric trajectories of ejected particles over thousands of years. The results show that Gault may be sensitive to structural failure at the current spin period (∼2.5 hr). Gault’s bulk density needs to be below 1.75 g cm−3 in order for particles on the equatorial surface to be shed owing to centrifugal forces. In this case, Gault requires cohesive strength of at least ∼200 Pa to maintain the structure at the center, whereas the surface strength needs to be less than ∼100 Pa to induce mass shedding. This suggests that Gault’s structure may consist of a weak surface layer atop a strong core. The trajectories of dust ejected from Gault depend on how efficiently they are accelerated by solar radiation pressure. Escaped particle clouds with sizes of < ∼100 μm could collide with Gault after ∼700–5300 yr with speeds of ∼0.2 km s−1. This implies a temporal increase in the impact flux and complex interactions between the ejected particles and their host body.

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“…Such an analysis is performed by tracking and modeling the OSIRIS-REx probe in orbit about the asteroid. In addition, because some particles are frequently ejected from Bennu [155], this analysis was improved by exploiting this characteristic, i.e., by tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits [260]. It was thus found that Bennu must have a heterogeneous mass distribution.…”

Section: C-type Near-earth Asteroids Ryugu and Bennumentioning

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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Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

Cited by 61 publications

References 67 publications

Rotational states and shapes of Ryugu and Bennu: Implications for interior structure and strength

Rotational states and shapes of Ryugu and Bennu: Implications for interior structure and strength

Active Main-belt Asteroid (6478) Gault: Constraint on Its Cohesive Strength and the Fate of Ejected Particles in the Solar System

Shapes, structures, and evolution of small bodies

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