{"id":10246,"date":"2021-11-23T08:47:00","date_gmt":"2021-11-23T13:47:00","guid":{"rendered":"http:\/\/all-geo.org\/highlyallochthonous\/?p=10246"},"modified":"2022-10-31T21:11:14","modified_gmt":"2022-11-01T02:11:14","slug":"weird-rocky-exoplanets","status":"publish","type":"post","link":"https:\/\/all-geo.org\/highlyallochthonous\/2021\/11\/weird-rocky-exoplanets\/","title":{"rendered":"Weird rocky exoplanets"},"content":{"rendered":"\n

Obtaining the composition of rocky exoplanets from the spectral signature produced when their dying parent star eats them<\/a> is already pretty mind-blowing. But the results – which suggest that on some of these worlds, quartz is substituted for olivine in their mantles? That\u2019s a mind-supernova.<\/p>\n\n\n\n

I\u2019m not even sure how you could get such a composition – coalescing from a particularly iron poor planetary nebula, perhaps? But given how Earth\u2019s mantle is dominated by olivine and its pressure-induced phase changes, there could be profound differences in how an olivine-free mantle convects and loses heat.<\/p>\n\n\n\n

As this figure from the paper shows<\/a>, the data also point to another kind of rocky exoplanet rich in periclase (MgO) rather than orthopyroxene. In other words, a significant non-silicate phase!<\/p>\n\n\n\n

\"\"
Figure 3 of Putirka & Xu (2021) plotting estimated compositions of exoplanetary mantles (large diamonds) on one of 3 ternary diagrams. Top left: components are Olivine, Orthopyroxene (Opx) and Clinopyroxene (Cpx), like the Earth’s mantle. Note how the light grey and dark grey diamonds plot way outside the ternary diagram, indicating at least one of the three components is not present. Centre: components are Quartz (replacing Olivine as in Earth’s continental crust), Opx, and Cpx. Bottom right: olivine, Cpx and periclase (MgO) replacing Opx.<\/figcaption><\/figure>\n\n\n\n

So what does this mean? The authors suggest that \u201cquartz-rich mantles might create thicker crusts, while the periclase-saturated mantles could plausibly yield, on a wet planet like Earth, crusts made of serpentinite.\u201d<\/p>\n\n\n\n

Of course, there are some sizeable (acknowledged) caveats, given the rather extreme detection method. We\u2019ll have to see whether these inferences stand up to scrutiny. But it’s yet more evidence that beyond our solar system, many surprises about the way planets work await.<\/p>\n\n\n\n

[This post was collated from this Twitter thread<\/a>]<\/p>\n","protected":false},"excerpt":{"rendered":"

Obtaining the composition of rocky exoplanets from the spectral signature produced when their dying parent star eats them is already pretty mind-blowing. But the results – which suggest that on some of these worlds, quartz is substituted for olivine in their … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,15,18],"tags":[308,427],"class_list":["post-10246","post","type-post","status-publish","format-standard","hentry","category-geology","category-planets","category-rocks-minerals","tag-exoplanets","tag-weird-geology"],"_links":{"self":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/10246","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/comments?post=10246"}],"version-history":[{"count":3,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/10246\/revisions"}],"predecessor-version":[{"id":10263,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/10246\/revisions\/10263"}],"wp:attachment":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/media?parent=10246"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/categories?post=10246"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/tags?post=10246"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}