LINK<\/strong><\/a><\/p>\n\n\n\n“The distinct accretionary histories of Earth and Mars \u2013 with Earth experiencing protracted growth and small contributions from outer solar system (carbonaceous, CC) materials, and Mars undergoing rapid growth with building materials drawn almost exclusively from the inner solar system (non-carbonaceous, NC) \u2013 highlight key differences in planetary formation. These contrasts underscore the importance of a comparative planetology framework for understanding the origin of volatiles in terrestrial planets. In this study, we examined the relationship between the carbon (C) isotopic compositions of planetary and planetesimal reservoirs to trace the origin of volatiles on Earth and Mars. The mean \u03b413C value of magmatic C in Martian meteorites (\u221220\u202f\u2030) is significantly lower than that of the bulk silicate Earth (BSE), with a canonical value of \u22125\u202f\u2030. While basaltic achondrites, magmatic iron meteorites, and ordinary chondrites from the NC reservoir display \u03b413C values similar to Martian meteorites, the BSE \u03b413C value is comparable to volatile-rich CC chondrites such as CI, CM, and CR, as well as with enstatite chondrites and ureilites from the NC reservoir. If Martian magmas underwent minimal C isotopic fractionation during degassing or degassed under kinetic conditions, then the \u03b413C value of the Martian mantle likely reflects accretion from thermally processed undifferentiated (ordinary chondrite-like) and differentiated NC materials. In contrast, if extensive degassing occurred via Rayleigh fractionation under equilibrium conditions, the \u03b413C value of the Martian mantle would have a higher \u03b413C value (\u221212 to \u221210\u202f\u2030) than that recorded in Martian meteorites \u2013 though still lighter than that of the canonical BSE \u03b413C. This implies a contribution from relatively 13C-rich NC materials, potentially similar to enstatite chondrites. For BSE, although the canonical \u03b413C value of \u20135\u202f\u2030 overlaps with those of enstatite chondrites and ureilites, the late-stage delivery of volatile-rich CC materials during the main phase of Earth\u2019s growth, which was critical for establishing its water and nitrogen inventories, likely biased its C isotopic composition towards a CC-like signature. However, a lower mean \u03b413C value of \u22128.4\u202f\u2030 of the MORB mantle, as proposed by recent studies, could mean that Earth\u2019s mantle still preserves the signature of 13C-poor, thermally processed NC materials accreted during the early stages of the planet\u2019s growth. The observed heterogeneity in mantle C isotopic compositions, similar to that seen in H and N isotopes, could therefore reflect a mixed contribution from both NC and CC materials. These findings suggest that the \u03b413C value of the BSE could be lower than the canonical estimate and may align more closely with the proposed value for the MORB mantle. Taken together, these findings suggest that the contrasting accretionary histories of Earth and Mars led to fundamentally different pathways for volatile acquisition. These divergent pathways likely shaped the long-term geochemical evolution of each planet and influenced their potential for habitability.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Damanveer S. Grewal, Sujoy Mukhopadhay Geochimica et Cosmochimica ActaAvailable online 12 September 2025 LINK “The distinct accretionary histories of Earth and Mars \u2013 with Earth experiencing protracted growth and small contributions from outer solar system…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[74,37,38,18,19,12,14,112,17,33,122,42,7,73,39],"tags":[1350,4819,250,80,2001,3729,3152,1858,2254,3572,1206,1088,369,4205],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39078"}],"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=39078"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39078\/revisions"}],"predecessor-version":[{"id":39079,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39078\/revisions\/39079"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=39078"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=39078"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=39078"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}