Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/29777
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dc.contributor.authorMichikami, Tatsuhiroen_UK
dc.contributor.authorHonda, Chikatoshien_UK
dc.contributor.authorMiyamoto, Hideakien_UK
dc.contributor.authorHirabayashi, Masatoshien_UK
dc.contributor.authorHagermann, Axelen_UK
dc.contributor.authorIrie, Terunorien_UK
dc.contributor.authorNomura, Keitaen_UK
dc.contributor.authorErnst, Carolyn Men_UK
dc.contributor.authorKawamura, Masakien_UK
dc.contributor.authorSugimoto, Kiichien_UK
dc.contributor.authorTatsumi, Erien_UK
dc.contributor.authorMorota, Tomokatsuen_UK
dc.contributor.authorHirata, Naruen_UK
dc.contributor.authorNoguchi, Takaakien_UK
dc.contributor.authorCho, Yuichiroen_UK
dc.date.accessioned2019-06-27T00:08:35Z-
dc.date.available2019-06-27T00:08:35Z-
dc.date.issued2019-10en_UK
dc.identifier.urihttp://hdl.handle.net/1893/29777-
dc.description.abstractIn 2018, the Japanese spacecraft Hayabusa2, arrived at the small asteroid Ryugu. The surface of this C-type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study. Using a few hundred Optical Navigation Camera (ONC) images with a pixel scale of approximately 0.65 m, we focus on boulders greater than 5m in diameter. Smaller boulders are also considered using five arbitrarily chosen ONC close-up images with pixel scales ranging from 0.7 to 6 cm. Across the entire surface area (~2.7 km2) of Ryugu, nearly 4400 boulders larger than 5m were identified. Boulders appear to be uniformly distributed across the entire surface, with some slight differences in latitude and longitude. At ~50 km−2, the number density of boulders larger than 20m is twice as large as on asteroid Itokawa (or Bennu). The apparent shapes of Ryugu's boulders resemble laboratory impact fragments, with larger boulders being more elongated. The ratio of the total volume of boulders larger than 5m to the total excavated volume of craters larger than 20m on Ryugu can be estimated to be ~94%, which is comparatively high. These observations strongly support the hypothesis that most boulders found on Ryugu resulted from the catastrophic disruption of Ryugu's larger parent body, as described in previous papers (Watanabe et al., 2019; Sugita et al.,2019). The cumulative size distribution of boulders larger than 5 m has a power-index of −2.65 ± 0.05, which is comparatively shallow compared with other asteroids visited by spacecraft. For boulders smaller than 4 m, the power-index is even shallower and ranges from −1.65 ± 0.05 to −2.01 ± 0.06. This particularly shallow power-index implies that some boulders are buried in Ryugu's regolith. Based on our observations, we suggest that boulders near the equator might have been buried by the migration of finer material and, as a result, the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes.en_UK
dc.language.isoenen_UK
dc.publisherElsevieren_UK
dc.relationMichikami T, Honda C, Miyamoto H, Hirabayashi M, Hagermann A, Irie T, Nomura K, Ernst CM, Kawamura M, Sugimoto K, Tatsumi E, Morota T, Hirata N, Noguchi T & Cho Y (2019) Boulder size and shape distributions on asteroid Ryugu. Icarus, 331, pp. 179-191. https://doi.org/10.1016/j.icarus.2019.05.019en_UK
dc.rights© 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).en_UK
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en_UK
dc.subjectAsteroidsen_UK
dc.subjectSurfacesen_UK
dc.subjectImpact processesen_UK
dc.subjectGeological processesen_UK
dc.subjectAsteroid Ryuguen_UK
dc.subjectRegolithsen_UK
dc.titleBoulder size and shape distributions on asteroid Ryuguen_UK
dc.typeJournal Articleen_UK
dc.identifier.doi10.1016/j.icarus.2019.05.019en_UK
dc.citation.jtitleIcarusen_UK
dc.citation.issn0019-1035en_UK
dc.citation.volume331en_UK
dc.citation.spage179en_UK
dc.citation.epage191en_UK
dc.citation.publicationstatusPublisheden_UK
dc.citation.peerreviewedRefereeden_UK
dc.type.statusVoR - Version of Recorden_UK
dc.contributor.funderSTFC Science & Technology Facilities Councilen_UK
dc.citation.date21/05/2019en_UK
dc.contributor.affiliationKindai Universityen_UK
dc.contributor.affiliationUniversity of Aizuen_UK
dc.contributor.affiliationUniversity of Tokyoen_UK
dc.contributor.affiliationAuburn Universityen_UK
dc.contributor.affiliationBiological and Environmental Sciencesen_UK
dc.contributor.affiliationKindai Universityen_UK
dc.contributor.affiliationKindai Universityen_UK
dc.contributor.affiliationJohns Hopkins Universityen_UK
dc.contributor.affiliationKindai Universityen_UK
dc.contributor.affiliationKindai Universityen_UK
dc.contributor.affiliationUniversity of Tokyoen_UK
dc.contributor.affiliationUniversity of Tokyoen_UK
dc.contributor.affiliationUniversity of Aizuen_UK
dc.contributor.affiliationKyushu Universityen_UK
dc.contributor.affiliationUniversity of Tokyoen_UK
dc.identifier.isiWOS:000473554600015en_UK
dc.identifier.scopusid2-s2.0-85066397340en_UK
dc.identifier.wtid1391520en_UK
dc.contributor.orcid0000-0002-1818-9396en_UK
dc.date.accepted2019-05-17en_UK
dcterms.dateAccepted2019-05-17en_UK
dc.date.filedepositdate2019-06-17en_UK
dc.relation.funderprojectHagermann Consolidated Grants: Make or Break & Comets in the laboratoryen_UK
dc.relation.funderrefST/S001271/1en_UK
rioxxterms.apcnot requireden_UK
rioxxterms.typeJournal Article/Reviewen_UK
rioxxterms.versionVoRen_UK
local.rioxx.authorMichikami, Tatsuhiro|en_UK
local.rioxx.authorHonda, Chikatoshi|en_UK
local.rioxx.authorMiyamoto, Hideaki|en_UK
local.rioxx.authorHirabayashi, Masatoshi|en_UK
local.rioxx.authorHagermann, Axel|0000-0002-1818-9396en_UK
local.rioxx.authorIrie, Terunori|en_UK
local.rioxx.authorNomura, Keita|en_UK
local.rioxx.authorErnst, Carolyn M|en_UK
local.rioxx.authorKawamura, Masaki|en_UK
local.rioxx.authorSugimoto, Kiichi|en_UK
local.rioxx.authorTatsumi, Eri|en_UK
local.rioxx.authorMorota, Tomokatsu|en_UK
local.rioxx.authorHirata, Naru|en_UK
local.rioxx.authorNoguchi, Takaaki|en_UK
local.rioxx.authorCho, Yuichiro|en_UK
local.rioxx.projectST/S001271/1|Science & Technology Facilities Council|en_UK
local.rioxx.freetoreaddate2019-06-17en_UK
local.rioxx.licencehttp://creativecommons.org/licenses/by/4.0/|2019-06-17|en_UK
local.rioxx.filenameMichikami-Etal-Icarus-2019-Boulder-size-and-shape-distributions-on-asteroid-Ryugu.pdfen_UK
local.rioxx.filecount1en_UK
local.rioxx.source0019-1035en_UK
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