Stabilization of ammonia-rich hydrate inside icy planets
The interior structure of the giant ice planets Uranus and Neptune, but also of newly discovered exoplanets, is loosely constrained, because limited observational data can be satisfied with various interior models. Although it is known that their mantles comprise large amounts of water, ammonia, and...
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Veröffentlicht in: | Proceedings of the National Academy of Sciences - PNAS 2017-08, Vol.114 (34), p.9003-9008 |
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description | The interior structure of the giant ice planets Uranus and Neptune, but also of newly discovered exoplanets, is loosely constrained, because limited observational data can be satisfied with various interior models. Although it is known that their mantles comprise large amounts of water, ammonia, and methane ices, it is unclear how these organize themselves within the planets—as homogeneous mixtures, with continuous concentration gradients, or as well-separated layers of specific composition. While individual ices have been studied in great detail under pressure, the properties of their mixtures are much less explored. We show here, using first-principles calculations, that the 2:1 ammonia hydrate, (H₂O)(NH₃)₂, is stabilized at icy planet mantle conditions due to a remarkable structural evolution. Above 65 GPa, we predict it will transform from a hydrogen-bonded molecular solid into a fully ionic phase
O
2
−
(
NH
4
+
)
2
, where all water molecules are completely deprotonated, an unexpected bonding phenomenon not seen before. Ammonia hemihydrate is stable in a sequence of ionic phases up to 500 GPa, pressures found deep within Neptune-like planets, and thus at higher pressures than any other ammonia–water mixture. This suggests it precipitates out of any ammonia–water mixture at sufficiently high pressures and thus forms an important component of icy planets. |
doi_str_mv | 10.1073/pnas.1706244114 |
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O
2
−
(
NH
4
+
)
2
, where all water molecules are completely deprotonated, an unexpected bonding phenomenon not seen before. Ammonia hemihydrate is stable in a sequence of ionic phases up to 500 GPa, pressures found deep within Neptune-like planets, and thus at higher pressures than any other ammonia–water mixture. This suggests it precipitates out of any ammonia–water mixture at sufficiently high pressures and thus forms an important component of icy planets.</description><identifier>ISSN: 0027-8424</identifier><identifier>EISSN: 1091-6490</identifier><identifier>DOI: 10.1073/pnas.1706244114</identifier><identifier>PMID: 28784809</identifier><language>eng</language><publisher>United States: National Academy of Sciences</publisher><subject>Ammonia ; Chemical bonds ; Concentration gradient ; Density ; Extrasolar planets ; Homogeneous mixtures ; Hydrogen bonding ; Hydrogen bonds ; Neptune ; Phase transitions ; Physical Sciences ; Planet detection ; Planetary interiors ; Planetary mantles ; Planets ; Precipitates ; Studies ; Uranus ; Water chemistry</subject><ispartof>Proceedings of the National Academy of Sciences - PNAS, 2017-08, Vol.114 (34), p.9003-9008</ispartof><rights>Volumes 1–89 and 106–114, copyright as a collective work only; author(s) retains copyright to individual articles</rights><rights>Copyright National Academy of Sciences Aug 22, 2017</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-a532t-f4647dbaf53e84e35eeaa75563584f51a0b0517904e4f241468f92c661ce689c3</citedby><cites>FETCH-LOGICAL-a532t-f4647dbaf53e84e35eeaa75563584f51a0b0517904e4f241468f92c661ce689c3</cites><orcidid>0000-0002-8971-3933</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://www.jstor.org/stable/pdf/26487282$$EPDF$$P50$$Gjstor$$H</linktopdf><linktohtml>$$Uhttps://www.jstor.org/stable/26487282$$EHTML$$P50$$Gjstor$$H</linktohtml><link.rule.ids>230,314,723,776,780,799,881,27901,27902,53766,53768,57992,58225</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/28784809$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Robinson, Victor Naden</creatorcontrib><creatorcontrib>Wang, Yanchao</creatorcontrib><creatorcontrib>Ma, Yanming</creatorcontrib><creatorcontrib>Hermann, Andreas</creatorcontrib><title>Stabilization of ammonia-rich hydrate inside icy planets</title><title>Proceedings of the National Academy of Sciences - PNAS</title><addtitle>Proc Natl Acad Sci U S A</addtitle><description>The interior structure of the giant ice planets Uranus and Neptune, but also of newly discovered exoplanets, is loosely constrained, because limited observational data can be satisfied with various interior models. Although it is known that their mantles comprise large amounts of water, ammonia, and methane ices, it is unclear how these organize themselves within the planets—as homogeneous mixtures, with continuous concentration gradients, or as well-separated layers of specific composition. While individual ices have been studied in great detail under pressure, the properties of their mixtures are much less explored. We show here, using first-principles calculations, that the 2:1 ammonia hydrate, (H₂O)(NH₃)₂, is stabilized at icy planet mantle conditions due to a remarkable structural evolution. Above 65 GPa, we predict it will transform from a hydrogen-bonded molecular solid into a fully ionic phase
O
2
−
(
NH
4
+
)
2
, where all water molecules are completely deprotonated, an unexpected bonding phenomenon not seen before. Ammonia hemihydrate is stable in a sequence of ionic phases up to 500 GPa, pressures found deep within Neptune-like planets, and thus at higher pressures than any other ammonia–water mixture. This suggests it precipitates out of any ammonia–water mixture at sufficiently high pressures and thus forms an important component of icy planets.</description><subject>Ammonia</subject><subject>Chemical bonds</subject><subject>Concentration gradient</subject><subject>Density</subject><subject>Extrasolar planets</subject><subject>Homogeneous mixtures</subject><subject>Hydrogen bonding</subject><subject>Hydrogen bonds</subject><subject>Neptune</subject><subject>Phase transitions</subject><subject>Physical Sciences</subject><subject>Planet detection</subject><subject>Planetary interiors</subject><subject>Planetary mantles</subject><subject>Planets</subject><subject>Precipitates</subject><subject>Studies</subject><subject>Uranus</subject><subject>Water chemistry</subject><issn>0027-8424</issn><issn>1091-6490</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2017</creationdate><recordtype>article</recordtype><recordid>eNpdkc1PGzEUxK2qVQkpZ06glbhw2eTZfv7YSyWE-oGE1AP0bDkbL3G0uw72Bin89XWUkFBOc5jfG73REHJOYUJB8emqt2lCFUiGSCl-IiMKFS0lVvCZjACYKjUyPCGnKS0BoBIavpITppVGDdWI6IfBznzrX-3gQ1-EprBdF3pvy-jrRbHYzKMdXOH75OdZ6k2xam3vhvSNfGlsm9zZXsfk788fj7e_y_s_v-5ub-5LKzgbygYlqvnMNoI7jY4L56xVQkguNDaCWpiBoKoCdNgwpCh1U7FaSlo7qauaj8n3Xe5qPevcvHb9EG1rVtF3Nm5MsN787_R-YZ7CixFCSU0xB1zvA2J4Xrs0mM6n2rXbGmGdDK2Y4iAUZxm9-oAuwzr2uV6mchGOQGmmpjuqjiGl6JrDMxTMdhWzXcUcV8kXl-87HPi3GTJwsQOWaQjx6EvUimnG_wF0ZZG5</recordid><startdate>20170822</startdate><enddate>20170822</enddate><creator>Robinson, Victor Naden</creator><creator>Wang, Yanchao</creator><creator>Ma, Yanming</creator><creator>Hermann, Andreas</creator><general>National Academy of Sciences</general><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7QG</scope><scope>7QL</scope><scope>7QP</scope><scope>7QR</scope><scope>7SN</scope><scope>7SS</scope><scope>7T5</scope><scope>7TK</scope><scope>7TM</scope><scope>7TO</scope><scope>7U9</scope><scope>8FD</scope><scope>C1K</scope><scope>FR3</scope><scope>H94</scope><scope>M7N</scope><scope>P64</scope><scope>RC3</scope><scope>7X8</scope><scope>5PM</scope><orcidid>https://orcid.org/0000-0002-8971-3933</orcidid></search><sort><creationdate>20170822</creationdate><title>Stabilization of ammonia-rich hydrate inside icy planets</title><author>Robinson, Victor Naden ; Wang, Yanchao ; Ma, Yanming ; Hermann, Andreas</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a532t-f4647dbaf53e84e35eeaa75563584f51a0b0517904e4f241468f92c661ce689c3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2017</creationdate><topic>Ammonia</topic><topic>Chemical bonds</topic><topic>Concentration gradient</topic><topic>Density</topic><topic>Extrasolar planets</topic><topic>Homogeneous mixtures</topic><topic>Hydrogen bonding</topic><topic>Hydrogen bonds</topic><topic>Neptune</topic><topic>Phase transitions</topic><topic>Physical Sciences</topic><topic>Planet detection</topic><topic>Planetary interiors</topic><topic>Planetary mantles</topic><topic>Planets</topic><topic>Precipitates</topic><topic>Studies</topic><topic>Uranus</topic><topic>Water chemistry</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Robinson, Victor Naden</creatorcontrib><creatorcontrib>Wang, Yanchao</creatorcontrib><creatorcontrib>Ma, Yanming</creatorcontrib><creatorcontrib>Hermann, Andreas</creatorcontrib><collection>PubMed</collection><collection>CrossRef</collection><collection>Animal Behavior Abstracts</collection><collection>Bacteriology Abstracts (Microbiology B)</collection><collection>Calcium & Calcified Tissue Abstracts</collection><collection>Chemoreception Abstracts</collection><collection>Ecology Abstracts</collection><collection>Entomology Abstracts (Full archive)</collection><collection>Immunology Abstracts</collection><collection>Neurosciences Abstracts</collection><collection>Nucleic Acids Abstracts</collection><collection>Oncogenes and Growth Factors Abstracts</collection><collection>Virology and AIDS Abstracts</collection><collection>Technology Research Database</collection><collection>Environmental Sciences and Pollution Management</collection><collection>Engineering Research Database</collection><collection>AIDS and Cancer Research Abstracts</collection><collection>Algology Mycology and Protozoology Abstracts (Microbiology C)</collection><collection>Biotechnology and BioEngineering Abstracts</collection><collection>Genetics Abstracts</collection><collection>MEDLINE - Academic</collection><collection>PubMed Central (Full Participant titles)</collection><jtitle>Proceedings of the National Academy of Sciences - PNAS</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Robinson, Victor Naden</au><au>Wang, Yanchao</au><au>Ma, Yanming</au><au>Hermann, Andreas</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Stabilization of ammonia-rich hydrate inside icy planets</atitle><jtitle>Proceedings of the National Academy of Sciences - PNAS</jtitle><addtitle>Proc Natl Acad Sci U S A</addtitle><date>2017-08-22</date><risdate>2017</risdate><volume>114</volume><issue>34</issue><spage>9003</spage><epage>9008</epage><pages>9003-9008</pages><issn>0027-8424</issn><eissn>1091-6490</eissn><abstract>The interior structure of the giant ice planets Uranus and Neptune, but also of newly discovered exoplanets, is loosely constrained, because limited observational data can be satisfied with various interior models. Although it is known that their mantles comprise large amounts of water, ammonia, and methane ices, it is unclear how these organize themselves within the planets—as homogeneous mixtures, with continuous concentration gradients, or as well-separated layers of specific composition. While individual ices have been studied in great detail under pressure, the properties of their mixtures are much less explored. We show here, using first-principles calculations, that the 2:1 ammonia hydrate, (H₂O)(NH₃)₂, is stabilized at icy planet mantle conditions due to a remarkable structural evolution. Above 65 GPa, we predict it will transform from a hydrogen-bonded molecular solid into a fully ionic phase
O
2
−
(
NH
4
+
)
2
, where all water molecules are completely deprotonated, an unexpected bonding phenomenon not seen before. Ammonia hemihydrate is stable in a sequence of ionic phases up to 500 GPa, pressures found deep within Neptune-like planets, and thus at higher pressures than any other ammonia–water mixture. This suggests it precipitates out of any ammonia–water mixture at sufficiently high pressures and thus forms an important component of icy planets.</abstract><cop>United States</cop><pub>National Academy of Sciences</pub><pmid>28784809</pmid><doi>10.1073/pnas.1706244114</doi><tpages>6</tpages><orcidid>https://orcid.org/0000-0002-8971-3933</orcidid><oa>free_for_read</oa></addata></record> |
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subjects | Ammonia Chemical bonds Concentration gradient Density Extrasolar planets Homogeneous mixtures Hydrogen bonding Hydrogen bonds Neptune Phase transitions Physical Sciences Planet detection Planetary interiors Planetary mantles Planets Precipitates Studies Uranus Water chemistry |
title | Stabilization of ammonia-rich hydrate inside icy planets |
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