{"id":27276,"date":"2021-04-08T14:25:35","date_gmt":"2021-04-08T12:25:35","guid":{"rendered":"https:\/\/karmaka.de\/?p=27276"},"modified":"2021-04-08T14:25:36","modified_gmt":"2021-04-08T12:25:36","slug":"thermal-metamorphism-of-cm-chondrites-a-dehydroxylation%e2%80%90based-peak%e2%80%90temperature-thermometer-and-implications-for-sample-return-from-asteroids-ryugu-and-bennu","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=27276","title":{"rendered":"Thermal metamorphism of CM chondrites: A dehydroxylation\u2010based peak\u2010temperature thermometer and implications for sample return from asteroids Ryugu and Bennu<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>Michael A. Velbel, Michael E. Zolensky<\/p>\n\n\n\n<p>Meteoritics &amp; Planetary Science<br>Version of Record online: 08 April 2021<\/p>\n\n\n\n<p><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/maps.13636\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK (OPEN ACCESS)<\/strong><\/a><br><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/epdf\/10.1111\/maps.13636\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p class=\"justify-text\">&#8220;The target bodies of C\u2010complex asteroid sample return missions are carbonaceous chondrite\u2010like near\u2010Earth asteroids (NEAs), chosen for the abundance and scientific importance of their organic compounds and \u201chydrous\u201d (including hydroxylated) minerals, such as serpentine\u2010group phyllosilicates. Science objectives include returning samples of pristine carbonaceous regolith from asteroids for study of the nature, history, and distribution of its constituent minerals, organic material, and other volatiles. Heating after the natural aqueous alteration that formed the abundant phyllosilicates in CM and similar carbonaceous chondrites dehydroxylated them and altered or decomposed other volumetrically minor constituents (e.g., carbonates, sulfides, organic molecules; Tonui et al. 2003, 2014). We propose a peak\u2010temperature thermometer based on dehydroxylation as measured by analytical totals from electron probe microanalysis (EPMA) of matrices in a number of heated and aqueously altered (but not further heated) CM chondrites. Some CM lithologies in Maribo and Sutter\u2019s Mill do not exhibit the matrix dehydroxylation expected for surface temperatures expected from insolation of meteoroids with their known orbital perihelia. This suggests that insolated\u2010heated meteoroid surfaces were lost by ablation during passage through Earth\u2019s atmosphere, and that insolation\u2010heated material is more likely to be encountered among returned asteroid regolith samples than in meteorites. More generally, several published lines of evidence suggest that episodic heating of some CM material, most likely by impacts, continued intermittently and locally up to billions of years after assembly and early heating of ancestral CM chondrite bodies. Mission spectroscopic measures of hydration can be used to estimate the extent of dehydroxylation, and the new dehydroxylation thermometer can be used directly to select fragments of returned samples most likely to contain less thermally altered inventories of primitive organic molecules.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Michael A. Velbel, Michael E. Zolensky Meteoritics &amp; Planetary ScienceVersion of Record online: 08 April 2021 LINK (OPEN ACCESS)PDF (OPEN ACCESS) &#8220;The target bodies of C\u2010complex asteroid sample return missions are carbonaceous chondrite\u2010like near\u2010Earth asteroids&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,2350,9,18,2243,96,576,552,181,62],"tags":[5719,3872,553,3273,105,3646,1595,141,330,4684,4899,1834,1843],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/27276"}],"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=27276"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/27276\/revisions"}],"predecessor-version":[{"id":27277,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/27276\/revisions\/27277"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=27276"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=27276"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=27276"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}