标题： 岩浆海洋在围绕M矮星运行的类地行星上维持地表水的作用 显示英文标题

标题： The Role of Magma Oceans in Maintaining Surface Water on Rocky Planets Orbiting M-Dwarfs

摘要： 围绕M矮星运行的类地行星（M-地球）目前是我们寻找生命迹象的最佳目标。 我们所知的生命需要水。 M-地球的宜居性受到水分流失到太空的威胁：年轻M矮星的高通量可以使原本宜居的行星失去3到20个地球海洋的水量。 我们开发了一个针对类地系外行星的0维箱型模型，这些行星位于宜居带内，在早期的地表岩浆洋阶段和更长的深层水循环阶段中追踪水分向太空的流失以及储层之间的交换。 一个关键特征是地表岩浆洋的持续时间，假设与失控温室效应同时发生。 这个时间尺度可以区分脱水行星、地幔脱水但表面有大量水的行星，以及地幔中藏有大量水的行星。 较长寿命的地表岩浆洋有助于M-地球保留水分：岩浆中溶解的水在宿主M矮星最早且最活跃的阶段提供了防止显著水分流失到太空的屏障，这取决于岩浆的饱和极限。 尽管短暂的地基岩浆洋可能有利于地表宜居性，但长期存在的地基岩浆洋可能会在地幔中储存大量水分，从而损害地表宜居性。 我们发现，岩浆洋和深层水循环可以在晚型M矮星宜居带内缘的类地行星上维持或恢复可居住的地表条件——如果这些行星形成时拥有少于${\sim}$10个地球海洋的水量，它们将变得脱水。 显示英文摘要

摘要： Earth-like planets orbiting M-dwarf stars, M-Earths, are currently the best targets to search for signatures of life. Life as we know it requires water. The habitability of M-Earths is jeopardized by water loss to space: high flux from young M-dwarf stars can drive the loss of 3--20 Earth oceans from otherwise habitable planets. We develop a 0-D box model for Earth-mass terrestrial exoplanets, orbiting within the habitable zone, which tracks water loss to space and exchange between reservoirs during an early surface magma ocean phase and the longer deep-water cycling phase. A key feature is the duration of the surface magma ocean, assumed concurrent with the runaway greenhouse. This timescale can discriminate between desiccated planets, planets with desiccated mantles but substantial surface water, and planets with significant water sequestered in the mantle. A longer-lived surface magma ocean helps M-Earths retain water: dissolution of water in the magma provides a barrier against significant loss to space during the earliest, most active stage of the host M-dwarf, depending on the water saturation limit of the magma. Although a short-lived basal magma ocean can be beneficial to surface habitability, a long-lived basal magma ocean may sequester significant water in the mantle at the detriment of surface habitability. We find that magma oceans and deep-water cycling can maintain or recover habitable surface conditions on Earth-like planets at the inner edge of the habitable zone around late M-dwarf stars -- these planets would otherwise be desiccated if they form with less than ${\sim}$10 terrestrial oceans of water.