A first look at Bennu and Ryugu for signatures of formation in the arrangements of its surface features
Abstract
The OSIRIS-REx spacecraft is scheduled to begin resolved imaging of Bennu in late October 2018 as part of its baseline mission. Earlier shape models of Bennu (e.g., Nolan et al. 2013) suggest an equatorial bulge, perhaps resulting from a faster spin period in the past (Scheeres et al., 2016) related to YORP. Hayabusa2 is returning detailed images of Ryugu, which also shows a top-shape asteroid with an equatorial bulge.
The shapes of these asteroids and others (e.g., 1999 KW4, Didymos) suggest migration of material away from mid-latitudes. In avalanche experiments of polydisperse grains, runoff material segregates into groupings with similar sizes, densities, and frictional attributes (Gray et al. 2015). Subsequent surface alterations on these bodies continue due to impacts, thermal effects, or spin-state evolution, but signatures of avalanches and mass-wasting may still be present. Numerical integration that applies careful treatment to the interactions between grains and to gravity—small, but still the dominant force present on these bodies—can capture certain essential properties of the surface and can facilitate interpretations of high-resolution topographical mapping made by The OSIRIS-REx and Hayabusa2 Teams. Taking into account the strategies employed in this area (e.g., Walsh et al., 2008; Hirabayashi et al. 2015; Zhang et al. 2017), we use our soft-sphere contact model (Schwartz et al. 2012) to simulate evolutionary scenarios using the n-body code pkdgrav (Stadel 2001; Richardson et al. 2000). We will report on preliminary numerical simulations to explore possible signatures of these evolutionary processes, attempting to bring into focus the process of equatorial bulge formation with comparisons to OSIRIS-REx and Hayabusa2 Spacecraft observational data. S.R.S. acknowledges support from NASA Grant no. 80NSSC18K0226 as part of the OSIRIS-REx Participating Scientist Program as well as the Complex Systems and Space, Environment, Risk and Resilience Academies of the Initiative d'EXcellence "Joint, Excellent, and Dynamic Initiative" (IDEX JEDI) of the Université Côte d'Azur. M.P. was supported by the Italian Space Agency (ASI) under agreement no. 2017-37-H.0. Additional support provided by JSPS International Planetary Network.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P21A..11S
- Keywords:
-
- 6040 Origin and evolution;
- PLANETARY SCIENCES: COMETS AND SMALL BODIESDE: 6055 Surfaces;
- PLANETARY SCIENCES: COMETS AND SMALL BODIESDE: 6205 Asteroids;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS