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arXiv 1609.04786astro-ph.EP
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地表-地幔水交换参数化对外行星海洋深度的影响

Effect of surface-mantle water exchange parameterizations on exoplanet ocean depths

Thaddeus D. Komacek, Dorian S. Abbot

摘要:

典型宜居带中的类地系外行星可能由于星子随机挥发性的传递而具有多种初始水分数。如果地球上的水总量很高,整个表面可能被水覆盖,形成一个“水世界”。“在一个具有活跃构造的行星上,竞争机制通过确定水在内部和表面之间的分配来调节表面上的水丰度。在这里,我们将探讨如何纳入不同的机制,脱气和再气化的水改变了挥发性演变的行星。对于所考虑的所有模型,挥发性循环在$\sim 2 \ \mathrm{Gyr}$之后达到近似稳态。使用这些稳态,我们发现,如果挥发性循环是完全依赖于温度或海底压力,系外行星需要高丰度(总质量的$\gtrsim 0.3\%$)的水有充分淹没的表面。然而,如果脱气更多地取决于海底压力,而再气主要取决于地幔温度,那么后期的脱气速率相对较大,并且在脱气和再气之间达到稳态,并具有大量的地表水分数。如果这种混合模型是物理的,那么总含水量与地球相似的超级地球可以成为水世界。因此,需要进一步了解推动类地行星挥发性循环的过程,以确定它们可能成为水世界的水含量。

英文摘要:

Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to random volatile delivery by planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld." On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. Here we explore how the incorporation of different mechanisms for the degassing and regassing of water changes the volatile evolution of a planet. For all of the models considered, volatile cycling reaches an approximate steady-state after $\sim 2 \ \mathrm{Gyr}$. Using these steady-states, we find that if volatile cycling is either solely dependent on temperature or seafloor pressure, exoplanets require a high abundance ($\gtrsim 0.3\%$ of total mass) of water to have fully inundated surfaces. However, if degassing is more dependent on seafloor pressure and regassing mainly dependent on mantle temperature, the degassing rate is relatively large at late times and a steady-state between degassing and regassing is reached with a substantial surface water fraction. If this hybrid model is physical, super-Earths with a total water fraction similar to that of the Earth can become waterworlds. As a result, further understanding of the processes that drive volatile cycling on terrestrial planets is needed to determine the water fraction at which they are likely to become waterworlds.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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