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

Abstract

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).

The Subsurface Coherent Rock Content of the Moon as Revealed by Cold‐Spot Craters

“…Such boulders were observed by astronauts at several craters (Muehlberger et al, ; Schmitt, ). However, extremely friable boulders are unlikely to have a thermal inertia as high as coherent blocks (boulders on Bennu and Ryugu have a low thermal inertia (DellaGiustina et al, ; Sugita et al, ) and may be an example of friable boulders), so we expect the contribution of breccia boulders to our results to be small. In contrast, impact melt is expected to have a high thermal inertia immediately after formation.…”

Photometry of Particles Ejected From Active Asteroid (101955) Bennu

“…If the particles are spherical and have typical Bennu values for p V and ρ , then D H and D η should agree. But for a Bennu global mean p V of 0.044 ± 0.011 (DellaGiustina et al, 2019) and presumed Bennu meteorite analog ρ of 2,000 ± 500 kg m −3 (Clark et al, 2011; Hamilton et al, 2019; Macke et al, 2011), the D H values are ~1.7× larger than the values of D η (Figure 6a).…”

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu

“…The event radiant locations contain abundant rocks that are diverse in size and surface texture, as well as small circular depressions that may be impact craters. However, similar features are globally distributed on Bennu (17,18).…”