{"id":38686,"date":"2025-07-04T13:37:46","date_gmt":"2025-07-04T11:37:46","guid":{"rendered":"https:\/\/karmaka.de\/?p=38686"},"modified":"2025-07-12T10:08:01","modified_gmt":"2025-07-12T08:08:01","slug":"dynamical-origin-of-theia-the-last-giant-impactor-on-earth","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=38686","title":{"rendered":"Dynamical origin of Theia, the last giant impactor on Earth<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>Duarte Branco, Sean N. Raymond, Pedro Machado<\/p>\n\n\n\n<p>Preprint submitted to Elsevier, 2 July 2025<\/p>\n\n\n\n<p><a href=\"https:\/\/arxiv.org\/pdf\/2507.01826\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p>Update (11 July 2025): Icarus, available online 11 July 2025  <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0019103525002726\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK + PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<ul>\n<li>We dynamically test the idea, derived from cosmochemical studies, that Theia may have been a carbonaceous (CC) object (Budde et al., 2019; Nimmo et al., 2024b)<\/li>\n\n\n\n<li>We ran N-body simulations of the late stages of terrestrial planet growth, including a tail of carbonaceous objects assumed to have been scattered inward during Jupiter and Saturn\u2019s accretion.<\/li>\n\n\n\n<li>Our dynamical simulations show that this scenario is plausible, as in roughly 50% of viable systems, Earth\u2019s last giant impactor is either a pure carbonaceous planetary embryo or a non-carbonaceous embryo that previously accreted carbonaceous material.<\/li>\n\n\n\n<li>We constrain the system parameters (CC mass and embryo:planetesimal mass ratio) for which a carbonaceous last giant impactor is viable<\/li>\n<\/ul>\n\n\n\n<p class=\"justify-text\">&#8220;Cosmochemical studies have proposed that Earth accreted roughly 5-10% of its mass from carbonaceous (CC) material, with a large fraction delivered late via its final impactor, Theia (the Moon-forming impactor). Here, we evaluate this idea using dynamical simulations of terrestrial planet formation, starting from a standard setup with a population of planetary embryos and planetesimals laid out in a ring centered between Venus and Earth&#8217;s orbits, and also including a population of CC planetesimals and planetary embryos scattered inward by Jupiter. We find that this scenario can match a large number of constraints, including i) the terrestrial planets&#8217; masses and orbits; ii) the CC mass fraction of Earth; iii) the much lower CC mass fraction of Mars, as long as Mars only accreted CC planetesimals (but no CC embryos); iv) the timing of the last giant (Moon-forming) impact; and v) a late accretion phase dominated by non-carbonaceous (NC) bodies. For this scenario to work, the total mass in scattered CC objects must have been ~ 0.2 &#8211; 0.3 \ud835\udc40\u2295 , with an embryo-to-planetesimal mass ratio of at least 8, and CC embryos in the ~ 0.01 &#8211; 0.05 \ud835\udc40\u2295 mass range. In that case, our simulations show there are roughly 50-50 odds of Earth&#8217;s last giant impactor (Theia) having been a carbonaceous object &#8211; either a pure CC embryo or an NC embryo that previously accreted a CC embryo. Our simulations thus provide dynamical validation of cosmochemical studies.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Duarte Branco, Sean N. Raymond, Pedro Machado Preprint submitted to Elsevier, 2 July 2025 PDF (OPEN ACCESS) Update (11 July 2025): Icarus, available online 11 July 2025 LINK + PDF (OPEN ACCESS) &#8220;Cosmochemical studies have&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[112,73],"tags":[3274,113,2888,695,257,1009,114],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/38686"}],"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=38686"}],"version-history":[{"count":2,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/38686\/revisions"}],"predecessor-version":[{"id":38730,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/38686\/revisions\/38730"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=38686"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=38686"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=38686"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}