{"id":41592,"date":"2026-05-05T16:14:35","date_gmt":"2026-05-05T14:14:35","guid":{"rendered":"https:\/\/karmaka.de\/?p=41592"},"modified":"2026-05-05T16:14:37","modified_gmt":"2026-05-05T14:14:37","slug":"fatigue-crack-formation-in-samples-from-asteroid-bennu-and-petrologic-controls-on-boulder-properties-and-evolution","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=41592","title":{"rendered":"Fatigue-crack formation in samples from asteroid Bennu and petrologic controls on boulder properties and evolution<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>J.L. Molaro, T.J. McCoy, A.J. Ryan, C.P. Opeil, C.G. Hoover, L.T.J. Hanton, A.R. Hildebrand, M. Patzek, C. El Mir, R. Wardell, T. Gooding, T.R. Rose, J. Biele, R.-L. Ballouz, R.J. Macke, H.C. Connolly Jr, D.S. Lauretta<\/p>\n\n\n\n<p>Icarus<br>Available online 5 May 2026, 117139<\/p>\n\n\n\n<p><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0019103526002058\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK +PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p>&#8220;Highlights<\/p>\n\n\n\n<ul>\n<li>Simulated thermal-fatigue cracks match observed cracks in hummocky Bennu samples.<\/li>\n\n\n\n<li>Crack types include grain-boundary, clast-boundary, and intergranular crack networks.<\/li>\n\n\n\n<li>Fatigue cracks result in the low thermal inertia of Bennu&#8217;s hummocky boulders.<\/li>\n\n\n\n<li>Regolith and boulders develop different cracks at different stages in their evolution.<\/li>\n\n\n\n<li>Porosity from cracks limited to boulder near-surfaces and formed in the recent epoch.&#8221;<\/li>\n<\/ul>\n\n\n\n<p class=\"justify-text\">&#8220;Thermal fatigue has been observed to be an important driver of boulder evolution on asteroid Bennu through the development of morphological features such as exfoliation flakes and linear fractures in response to diurnal cycling. While the formation of these features has been explored through boulder-scale simulations of mechanical stress fields, fatigue is a multiscale process. Grain-scale effects associated with mineral heterogeneity play an important role in the propagation of microcracks which ultimately produce the larger scale features, as well as in the evolution of the thermal and mechanical properties of the boulder material. In this work, we investigate how the composition and texture of Bennu&#8217;s material influences fatigue crack propagation by simulating thermal stress fields in samples under different thermal conditions. Our results predict the formation of intergranular crack networks and grain- and clast-boundary cracks in boulders and regolith particles on Bennu and are well-matched by observed cracks and pore spaces observed in Bennu samples with hummocky morphologies. We posit that ongoing and active thermal fatigue is a primary driver of the difference in macro- and microscale porosity observed between hummocky and angular boulders on Bennu&#8217;s surface, and that these morphologies represent end members on a spectrum of mechanical properties. The contribution of fatigue cracking to the low thermal inertia observed in hummocky boulders is likely to be limited to their near-surfaces and to have originated during the recent epoch after Bennu migrated to near-Earth space. The different types of cracks which develop under different thermal conditions also occur at different stages in the material lifetime and will act together with boulder-scale effects in a cyclic and iterative breakdown process. The nature of fracture formation in these materials is strongly controlled by their unique structure and composition, which has important implications for understanding boulder and regolith evolution across the asteroid population.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>J.L. Molaro, T.J. McCoy, A.J. Ryan, C.P. Opeil, C.G. Hoover, L.T.J. Hanton, A.R. Hildebrand, M. Patzek, C. El Mir, R. Wardell, T. Gooding, T.R. Rose, J. Biele, R.-L. Ballouz, R.J. Macke, H.C. Connolly Jr, D.S&#8230;.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,552,1184],"tags":[5719,1854,263,1771,2058,4899,4343],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41592"}],"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=41592"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41592\/revisions"}],"predecessor-version":[{"id":41593,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41592\/revisions\/41593"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41592"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41592"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}