论文标题
碳化物系外行星内部的氧化
Oxidation of the Interiors of Carbide Exoplanets
论文作者
论文摘要
天体物理测量表明，有些恒星具有足够高的碳与氧比，因此它们托管的行星主要由碳化物而不是硅酸盐组成。我们研究了在与激光加热的钻石 - Anvil细胞（LHDAC）中与行星内部相关的高压温度条件下的水中存在碳化硅的行为。当与水反应时，碳化硅碳化物将二氧化硅（Stishovite）和钻石转化为高达50 GPA的压力，温度高达2500 K：SIC + 2H $ _2 $ _2 $> SIO $ _2 $ _2 $ + C + C + 2H $ _2 $。因此，如果可以在碳化物行星形成期间或通过以后的递送中掺入水中，则可以将它们氧化并以矿物质和钻石为主的矿物学氧化。该反应可能会在较浅的深度和h $ _2 $上产生Ch $ _4 $，在更大的深度可以从内部脱气，从而导致转化后的碳行星的大气丰富，以减少气体。反应后多余的水可以存储在转化后碳行星内部的密集二氧化硅多晶型物中。将矿物学转化为钻石和硅酸盐的转化会降低富含碳的行星的密度，从而使经过2-8个地球质量范围的质量 - 拉迪乌斯关系中的转化行星与硅酸盐行星不同。
Astrophysical measurements have shown that some stars have sufficiently high carbon-to-oxygen ratios such that the planets they host would be mainly composed of carbides instead of silicates. We studied the behavior of silicon carbide in the presence of water under the high pressure-temperature conditions relevant to planetary interiors in the laser-heated diamond-anvil cell (LHDAC). When reacting with water, silicon carbide converts to silica (stishovite) and diamond at pressures up to 50 GPa and temperatures up to 2500 K: SiC + 2H$_2$O -> SiO$_2$ + C + 2H$_2$. Therefore, if water can be incorporated into carbide planets during their formation or through later delivery, they could be oxidized and have mineralogy dominated by silicates and diamond in their interiors. The reaction could produce CH$_4$ at shallower depths and H$_2$ at greater depths which could be degassed from the interior, causing the atmospheres of the converted carbon planets to be rich in reducing gases. Excess water after the reaction can be stored in dense silica polymorphs in the interiors of the converted carbon planets. Such conversion of mineralogy to diamond and silicates would decrease the density of carbon-rich planet, making the converted planets distinct from silicate planets in mass-radius relations for the 2-8 Earth mass range.
