Metallic rubble piles can preserve large enough porosities to explain the densities of M-type asteroids like Psyche and Kleopatra”<\/li><\/ul>\n\n\n\n“Models of asteroid collisional evolution suggest that many asteroids are gravitationally-bound rubble piles. Although rubble piles may be expected to retain large void fractions, compaction may reduce the porosity. We apply models for cold compaction of rubble-pile bodies developed in a companion paper toward observations of asteroid densities. The model for chondritic boulders is applied to S-type (stony) and C-type (carbonaceous) asteroids. The relation between density and size of S-type asteroids is largely explained by cold compaction of rubble piles through fracturing of boulders, under the assumption that boulder size distributions are narrow before fracturing and fractal-like afterward. The density variation of C-type asteroids can only partly be explained by this mechanism, and the removal of micro-voids inside the boulders would be required to match observations. The model for metal boulders is applied to M-type asteroids, and the results suggest that, because of cold welding between metal boulders and the high yield strength of metal for either ductile or brittle-like deformation, metallic rubble piles can preserve large (\u227350%) porosities if the boulders are \u223c1 m in size. This implies that M-type asteroids such as Psyche and Kleopatra may be purely metallic, even though their densities are less than half that of iron. We also consider the hypothesis that Psyche is a primitive body of a CB chondrite-like material. Assuming that the strength of CB chondrite is controlled by a silicate matrix, we predict that the density of a Psyche-sized rubble pile of CB chondrite is higher than that of Psyche.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Zhongtian Zhang, David Bercovici, Linda Elkins-Tanton JGR PlanetsFirst published: 07 October 2022 LINK “Key Points We model cold compaction in stony and metallic rubble piles, under the assumption of initially narrow boulder size distributions Stony…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,584,2495,5891,1184],"tags":[2496,1854,4599,1771,2058,6383,1019,6353],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31351"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=31351"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31351\/revisions"}],"predecessor-version":[{"id":31352,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31351\/revisions\/31352"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=31351"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=31351"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=31351"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}