Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

Barnouin, Olivier S.; Daly, M. G.; Palmer, E. E.; Gaskell, R. W.; Weirich, J. R.; Johnson, C. L.; Asad, M. M. Al; Roberts, J. H.; Perry, M. E.; Susorney, H. C. M.; Daly, R. T.; Bierhaus, E. B.; Seabrook, J. A.; Espiritu, R. C.; Nair, Hari; Nguyen, L.; Neumann, Gregory A.; Ernst, C. M.; Boynton, W. V.; Nolan, M. C.; Adam, Coralie D.; Moreau, Michael C.; Rizk, B.; d’Aubigny, C. Drouet; Jawin, E. R.; Walsh, K. J.; Michel, Patrick; Schwartz, S. R.; Ballouz, Ronald-Louis; Mazarico, E.; Scheeres, Daniel J.; McMahon, Jay W.; Bottke, W. F.; Sugita, Seiji; Hirata, Naoyuki; Watanabe, S.; Burke, K. N.; DellaGiustina, D. N.; Bennett, C. A.; Лауретта, Д. С.

doi:10.1038/s41561-019-0330-x

Cited by 201 publications

(276 citation statements)

References 37 publications

(41 reference statements)

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“…The model itself does not set a spatial scale for this roughness; it can be anywhere between the resolution of the shape model used for the thermal analysis (~12 m) and the diurnal thermal skin depth (~2 cm, methods), though we expect that roughness at the smaller length scales dominates the thermal signature [43]. From the shape model of Bennu [3], we find RMS slopes that increase with decreasing spatial scale. Extrapolation of a power-law fit to roughness estimates from the shape model at four spatial scales fits the measured thermal roughness at a spatial scale of ~2 cm ( Supplementary Fig.…”

Section: Evidence Of Particulate Regolithmentioning

confidence: 89%

“…The longest axis dimension was measured; for simplicity we refer to this as boulder diameter. The position of polyline geometries are linked to the bodyfixed Cartesian coordinates from OCAMS geometric backplanes, which were calculated using the ISIS3 spiceinit routine and the v13 shape model of Bennu, with an average facet size of 75 cm [3]. The polyline endpoints and the midpoint are recorded and used to calculate boulder length.…”

Section: Boulder Size-frequency Distribution and Albedo Calculationsmentioning

confidence: 99%

“…Thus, measurement uncertainty for individual boulders is captured as the square-root of the number of boulders greater than or equal to D, normalized by surface area. We use surface area of 0.786 km 2 derived from the v13 shape model [3].…”

Section: Boulder Size-frequency Distribution and Albedo Calculationsmentioning

confidence: 99%

“…In late 2018, the OSIRIS-REx spacecraft rendezvoused with asteroid (101955) Bennu and acquired remotely sensed image and spectral data. The OSIRIS-REx Camera Suite (OCAMS [2]) PolyCam panchromatic camera confirmed the top-like shape of the asteroid [3] and imaged the surface at scales down to 0.33 m/pixel, while the MapCam instrument imaged at scales down to 1.1 m/pixel in four colors and a panchromatic filter. The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS [4]) and the OSIRIS-REx Thermal Emission Spectrometer (OTES [5]) measured disk-integrated spectra covering a full asteroid rotation before Bennu filled their respective fields of view.…”

mentioning

confidence: 95%

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Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis

et al. 2019

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Christensen, P. R.; Drouet d'Aubigny, C. Y.; Hamilton, V. E.; Reuter, D. C.; Rizk, B.; Simon, A. A.; Asphaug, E.; Bandfield, J. L.; Barnouin, O. S.; Barucci, M. A.; Bierhaus, E. B.; Binzel, R. P.; Bottke, W. F.; Bowles, N. E.; Campins, H.; Clark, B. C.; Clark, B. E.; Connolly, H. C.; Daly, M. G.; Leon, J. de; Delbo', M.; Deshapriya, J. D. P.; Elder, C. M.; Fornasier, S.; Hergenrother, C. W.; Howell, E. S.; Jawin, E. R.; Kaplan, H. H.; Kareta, T. R.; Le Corre, L.; Li, J.-Y.; Licandro, J.; Lim, L. F.; Michel, P.; Molaro, J.; Nolan, M. C.; Pajola, M.; Popescu, M.; Garcia, J. L. Rizos; Ryan, A.; Schwartz, S. R.; Shultz, N.; Siegler, M. A.; Smith, P. H.; Tatsumi, E.; Thomas, C. A.; Walsh, K. J.; Wolner, C. W. V.; Zou, X.-D. and Lauretta, D. S. (2019). Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis. Nature Astronomy, 3 pp. 341-351. For guidance on citations see FAQs.Length of main text: 2956 words Length of methods: 3605 words Length of legends: 565 words Number of references: 53 main text, 69 including methods and supplementary information (refs 67 to 69 are cited in the SI only) , we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micron-scale particles).

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Section: Evidence Of Particulate Regolithmentioning

confidence: 89%

Section: Boulder Size-frequency Distribution and Albedo Calculationsmentioning

confidence: 99%

Section: Boulder Size-frequency Distribution and Albedo Calculationsmentioning

confidence: 99%

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confidence: 95%

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Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis

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“…We consider that Phaethon has a mean equatorial diameter of 6.25 km and an oblateness (the ratio of semi-minor axis to semi-major axis) of 0.889, which is the same as Bennu's (Barnouin et al 2019). We note that Taylor et al (2019) did not specify the oblateness of Phaethon but implied that it would be similar to that of Bennu.…”

Section: Semi-analytical Model For Structural Failure In a Top-shapedmentioning

confidence: 99%

Mass-shedding Activities of Asteroid (3200) Phaethon Enhanced by Its Rotation

Nakano

Hirabayashi

2020

ApJL

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Asteroid (3200) Phaethon, a B-type asteroid, has been active during its perihelion passages. This asteroid is considered to be a source of the Geminid meteor stream. It is reported that this asteroid is spinning at a rotation period of 3.60 hr and has a top shape (an oblate body with an equatorial ridge) with a mean equatorial diameter of 6.25 km. Here, we report that Phaethon's rotation state may be close to or above its critical rotation period when the bulk density is 0.5 − 1.5 g/cm 3 (a typical bulk density of a B-type asteroid). We found that in this condition, the structure of Phaethon is sensitive to failure unless the cohesive strength is ∼50 P a − ∼260 P a. This result implies that if there are some surface processes driven by, for example, thermal waves, large-scaled deformation may happen and cause mass shedding. From this interpretation, we propose the processes that produced the Geminid meteor stream in the past and dust tails recently. Phaethon initially rotated at a spin period shorter than the current period. The magnitude of structural deformation at this stage was higher than the present spin condition, and a large mass shedding event, i.e., the Geminid meteor stream, occurred. After this deformation process, the body became more oblate, and its spin slowed down. At this point, while the spin was high enough for the body to have mass shedding events, the magnitude of these events became small.

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