The Western Bulge of 162173 Ryugu Formed as a Result of a Rotationally Driven Deformation Process
Scheeres, Daniel J.
Barnouin, Olivier S.
Schwartz, Stephen R.
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PublisherIOP PUBLISHING LTD
CitationMasatoshi Hirabayashi et al 2019 ApJL 874 L10
JournalASTROPHYSICAL JOURNAL LETTERS
Rights© 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
Abstract162173 Ryugu, the target of Hayabusa2, has a round shape with an equatorial ridge, which is known as a spinning top shape. A strong centrifugal force is a likely contributor to Ryugu's top-shaped features. Observations by the Optical Navigation Camera on board Hayabusa2 show a unique longitudinal variation in geomorphology; the western side of this asteroid, later called the western bulge, has a smooth surface and a sharp equatorial ridge, compared to the other side. Here, we propose a structural deformation process that generated the western bulge. Applying the mission-derived shape model, we employ a finite element model technique to analyze the locations that experience structural failure within the present shape. Assuming that materials are uniformly distributed, our model shows the longitudinal variation in structurally failed regions when the spin period is shorter than similar to 3.75 hr. Ryugu is structurally intact in the subsurface region of the western bulge while other regions are sensitive to structural failure. We infer that this variation is indicative of the deformation process that occurred in the past, and the western bulge is more relaxed structurally than the other region. Our analysis also shows that this deformation process might occur at a spin period between similar to 3.5 and similar to 3.0 hr, providing the cohesive strength ranging between similar to 4 and similar to 10 Pa.
VersionFinal published version
SponsorsAuburn University; French space agency CNES; Academies of Excellence: Complex systems and Space, environment, risk and resilience, part of the IDEX JEDI of the Universite Cote d'Azur; JSPS; Center For Planetary Origins; NEC corporation