English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We examine the possibility that icy super-Earth mass planets, formed overlong time scales (0.1--1~Gyr) at large distances ($\sim$ 200--1000~AU) fromtheir host stars, will develop massive H-rich atmospheres. Within the interiorof these planets, high pressure converts CH$_4$ into ethane, butane, or diamondand releases H$_2$. Using simplified models which capture the basic physics ofthe internal structure, we show that the physical properties of the atmospheredepend on the outflux of H$_2$ from the mantle. When this outflux is $\lesssim10^{10}$ [molec cm$^{-2}$ s$^{-1}$], the outgassed atmosphere has base pressure$\lesssim$ 1 bar. Larger outflows result in a substantial atmosphere where thebase pressure may approach $10^3 - 10^4$ bar. For any pressure, the meandensity of these planets, 2.4--3 [g cm$^{-3}$], is much larger than the meandensity of Uranus and Neptune, 1.3--1.6 [g cm$^{-3}$]. Thus, observations candistinguish between a Planet Nine with a primordial H/He-rich atmosphereaccreted from the protosolar nebula and one with an atmosphere outgassed fromthe core.

H-Atmospheres of Icy Super-Earths Formed in situ in the Outer Solar System: An Application to a Possible Planet Nine