LINK<\/strong><\/a><\/p>\n\n\n\n“The bombardment of impactors (leftover planetesimals, asteroids and comets) created numerous impact craters on the Moon. The giant planets in the outer Solar System are believed to have experienced a dynamical instability, in which the migration of giant planets delivers impactors to the inner Solar System bodies. The difference between the population of large (diameter more than ~5\u2009km) impact craters observed on heavily cratered lunar highlands and that on the lunar maria was thought to support the lunar Late Heavy Bombardment, which started ~0.6 billion years after planet formation and could have been caused by the late instability of giant planets. However, large craters on various-aged lunar surfaces have similar size\u2013frequency distributions when considering the preferential erasure of small craters. In addition, dynamical and geochemical evidence favour an early instability of giant planets at ~4.5\u2009Gyr ago. Here, we report the evolution at geological scales of regolith thickness on the Moon, which is a proxy for the change of the size\u2013frequency distribution slope for Earth\u2013Moon impactors with diameters less than ~50\u2009m (which generate craters with diameters less than ~1\u2009km (ref. 10)). We found an abnormally slow growth of regolith thickness per unit of impact flux before 3.5+0.3\u22120.6\u2009Gyr ago (3\u03c3 uncertainty), which can best be explained by a population of craters of less than ~1\u2009km whose size\u2013frequency distribution had a shallower power-law slope (\u22122.57+0.30\u22120.16) than that afterward (\u22123.24+0.03\u22120.06). The transition time at ~3.5\u2009Gyr ago supports the early instability of giant planets, in which dominant Earth\u2013Moon impactors changed from leftover planetesimals to asteroids5. The value of \u22123.24 is consistent with the preferential delivery of small asteroids via Yarkovsky\u2013YORP effects.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Minggang Xie, Zhiyong Xiao, Luyuan Xu, Wenzhe Fa & Aoao Xu Nature Astronomy (2020), Published: 09 November 2020 LINK “The bombardment of impactors (leftover planetesimals, asteroids and comets) created numerous impact craters on the Moon….<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,3177,112,90,115,71],"tags":[1573,80,944,2553,2888,1866,1857,257],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25328"}],"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=25328"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25328\/revisions"}],"predecessor-version":[{"id":25329,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25328\/revisions\/25329"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25328"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25328"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25328"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}