{"id":20231,"date":"2019-08-08T15:44:43","date_gmt":"2019-08-08T13:44:43","guid":{"rendered":"http:\/\/karmaka.de\/?p=20231"},"modified":"2019-08-08T15:44:44","modified_gmt":"2019-08-08T13:44:44","slug":"exposure-experiments-of-amorphous-silicates-and-organics-to-cometary-ice-and-vapor-analogs","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=20231","title":{"rendered":"Exposure Experiments of Amorphous Silicates and Organics to Cometary Ice and Vapor Analogs<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>Aki Takigawa, Yoshihiro Furukawa, Yuki Kimura, Bj\u00f6rn Davidsson, and Tomoki Nakamura<\/p>\n\n\n\n<p>The Astrophysical Journal, Volume 881, Number 1<br>\nPublished 2019 August 8 <\/p>\n\n\n\n<p><a href=\"https:\/\/iopscience.iop.org\/article\/10.3847\/1538-4357\/ab27c6\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK (OPEN ACCESS)<\/strong><\/a><br>\n<a href=\"https:\/\/iopscience.iop.org\/article\/10.3847\/1538-4357\/ab27c6\/pdf\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p class=\"justify-text\">&#8220;Hydration is a major mineral alteration process in primitive asteroids and it might occur in comet nuclei; however, it is poorly understood at low temperatures, especially below the freezing point of water. Long-duration experiments were performed with exposures of amorphous silicate nanoparticles and organic compounds (glycine and ribose) to D2O and D2O + NH3 ices and vapors at temperatures of \u221217\u00b0C and \u221227\u00b0C for 10\u2013120 days; and with exposure of amorphous silicates to H2O vapor\/liquid at &gt;25\u00b0C for 10 days. The amorphous silicates were analyzed by X-ray diffraction and Fourier-transform infrared spectroscopy, and recovery of organic molecules was determined by liquid chromatography\u2013mass spectrometry. No hydration of amorphous silicates or organic compounds was observed after exposure at temperatures below \u221217\u00b0C for 120 days to ices with or without NH3, whereas hydration of the amorphous silicates was observed in experiments above room temperature. The estimated thermal history of the nucleus of the short-period comet 67P\/Churyumov\u2013Gerasimenko indicates that the surface temperature does not exceed \u221245\u00b0C, even in a region exposed to strong solar illumination during the perihelion passage. Assuming hydration is controlled by the collision frequency between H2O molecules and dust particles, the present results indicate that cometary dust does not hydrate for more than 25\u2013510 periods of comet 67P. This is consistent with the absence of phyllosilicates on 67P and suggests that amino acids and sugars have not been altered.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Aki Takigawa, Yoshihiro Furukawa, Yuki Kimura, Bj\u00f6rn Davidsson, and Tomoki Nakamura The Astrophysical Journal, Volume 881, Number 1 Published 2019 August 8 LINK (OPEN ACCESS) PDF (OPEN ACCESS) &#8220;Hydration is a major mineral alteration process&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[613,1865,1211,1854,1870,2408,251,815,232,330,370,2693],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20231"}],"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=20231"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20231\/revisions"}],"predecessor-version":[{"id":20232,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20231\/revisions\/20232"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=20231"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=20231"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=20231"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}