LINK<\/strong><\/a><\/p>\n\n\n\n“The large variations in hydrogen isotope ratios found in insoluble organic matter (IOM) in chondritic meteorites may be attributed to hydrogen isotopic exchange between IOM and water during aqueous alteration. We conducted D\u2013H exchange experiments (1) during synthesis of IOM simulant (hereafter called chondritic organic analog, COA) from formaldehyde, glycolaldehyde, and ammonia with water, and (2) with the synthesized COA with a secondary reservoir of water. The changes in the D\/H ratios obtained by infrared spectra of the COA suggest that most of the hydrogen in the COA is derived from water during synthesis. We further investigated the kinetics of D\u2013H exchange between D\u2010rich COA and D\u2010poor water, as well as the opposite case, D\u2010poor COA and D\u2010rich water. To help assess understanding exchange kinetics, two\u2010dimensional isotope imaging obtained using isotope microscope revealed that no gradient D\u2013H exchange profiles were present in the COA grains, indicating that the rate\u2010limiting step for D\u2013H exchange is not diffusion. Thus, the changes in D\/(D + H) ratios were fit by the first\u2010order reaction rate law. Apparent kinetic parameters\u2014the rate constants, the activation energies, and the frequency factors\u2014were obtained with the Arrhenius equation. Using these kinetic expressions, hydrogen isotopic exchange profiles were estimated for time and temperature behavior. The D\u2013H exchange between organic matter and water is apparently relatively fast and this implies that the aqueous alteration temperatures should have been very low, likely close to 0 \u00b0C to maintain hydrogen isotopic disequilibrium between organic matter and liquid water for millions of years.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Yoko Kebukawa, Sachio Kobayashi, Noriyuki Kawasaki, Ying Wang, Hisayoshi Yurimoto, George D. Cody Meteoritics & Planetary ScienceVersion of Record online: 09 March 2021 LINK “The large variations in hydrogen isotope ratios found in insoluble organic…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61,576,81],"tags":[1842,1684,743,1989,1859,1855],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26870"}],"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=26870"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26870\/revisions"}],"predecessor-version":[{"id":26871,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26870\/revisions\/26871"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=26870"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=26870"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=26870"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}