The Astrophysical Journal Letters<\/a>.<\/p>\nThe researchers assume that, in an early stage of their formation, the sub-Neptunes went through a phase in which they were covered by a deep, hot magma ocean. A shell of hydrogen gas ensured that this phase was maintained for millions of years.<\/p>\n
\u201cIn our study, we investigated how the chemical interactions between magma oceans and atmospheres affect the water content of young sub-Neptune exoplanets,\u201d says Werlen.<\/p>\n
To do this, the researchers used an existing model that describes planetary evolution over a specific period of time. They combined this with a new model that calculates the chemical processes that take place between the gas in the atmosphere, and the metals and silicates in the magma.<\/p>\n
The researchers calculated the chemical equilibrium state of 26 different components for a total of 248 model planets. The computer simulations showed that the chemical processes destroy most H2O water molecules. Hydrogen (H) and oxygen (O) attach themselves to metallic compounds, and these largely disappear into the planet\u2019s core.<\/p>\n
Even though the accuracy of such calculations has some limitations, the researchers are convinced by the results.<\/p>\n
\u201cWe focus on the major trends and can clearly see in the simulations that the planets have much less water than they originally accumulated,\u201d explains Werlen. \u201cThe water that actually remains on the surface as H2O is limited to a few per cent at most.\u201d<\/p>\n
In an earlier publication, Dorn\u2019s group was already able to show how most of a planet\u2019s water is hidden in the interior.<\/p>\n
\u201cIn the current study, we analyzed how much water there is in total on these sub-Neptunes,\u201d explains the researcher, \u201cAccording to the calculations, there are no distant worlds with massive layers of water where water makes up around 50% of the planet\u2019s mass, as was previously thought. Hycean worlds with 10-90% water are therefore very unlikely.\u201d<\/p>\n
This makes the search for extra-terrestrial life more difficult than hoped for. Conditions conducive to life, with sufficient liquid water on the surface, are likely to exist only on smaller planets, which will probably be observable only with observatories even better than the James Webb Space Telescope.<\/p>\n
Dorn finds the role of our Earth particularly exciting in light of the new calculations which show that most distant planets have similar water content to our planet.<\/p>\n
\u201cThe Earth may not be as extraordinary as we think. In our study, at least, it appears to be a typical planet,\u201d she says.<\/p>\n
The researchers were also surprised by a seemingly paradoxical difference: the planets with the most water-rich atmospheres are not those that have accumulated the most ice beyond the snow line, but rather planets that formed within the snow line. On these planets, the water did not come from ice crystals, but was produced chemically when hydrogen in the planetary atmosphere reacted with oxygen from the silicates in the magma ocean to form H2O molecules.<\/p>\n
\u201cThese findings challenge the classic link between ice-rich formation and water-rich atmospheres. Instead, they highlight the dominant role of the equilibrium between magma ocean and atmosphere in shaping planetary composition,\u201d concludes Werlen. This will have far-reaching implications for theories of planetary formation and the interpretation of exoplanetary atmospheres in the age of the James Webb Telescope.<\/p>\n
Source: ETH Zurich<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Share this Article You are free to share this article under the Attribution 4.0 International license. There is…\n","protected":false},"author":2,"featured_media":79297,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[18,6123,19,17,133,451,447],"class_list":{"0":"post-79296","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-eire","9":"tag-exoplanets","10":"tag-ie","11":"tag-ireland","12":"tag-science","13":"tag-space","14":"tag-water"},"share_on_mastodon":{"url":"","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/79296","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=79296"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/79296\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/79297"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=79296"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=79296"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=79296"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}