The water content of magma oceans is widely accepted as a key factor that determines whether a terrestrial planet is habitable. Water ocean mass is determined as a result not only of water delivery and loss, but also of water partitioning among several reservoirs. Here we review our current understanding of water partitioning among the atmosphere, magma ocean, and solid mantle of accreting planetary embryos and protoplanets just after giant collisions. Magma oceans are readily formed in planetary embryos and protoplanets in their accretion phase. Significant amounts of water are partitioned into magma oceans, provided the planetary building blocks are water-rich enough. Particularly important but still quite uncertain issues are how much water the planetary building blocks contain initially and how water goes out of the solidifying mantle and is finally degassed to the atmosphere. Constraints from both solar-system explorations and exoplanet observations and also from laboratory experiments are needed to resolve these issues.

中文翻译：

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具有岩浆海洋的行星胚胎和原行星中的水分配

岩浆海洋的含水量被广泛认为是决定类地行星是否宜居的关键因素。水海洋质量不仅取决于水的输送和损失，还取决于水在几个水库之间的分配。在这里，我们回顾了我们目前对大气、岩浆海洋和刚刚发生巨大碰撞后正在吸积的行星胚胎和原行星的固体地幔之间的水分配的理解。岩浆海洋很容易在行星胚胎和原行星的吸积阶段形成。大量的水被划分为岩浆海洋，前提是行星构建块的水足够丰富。特别重要但仍然相当不确定的问题是行星构建块最初含有多少水，以及水如何从凝固的地幔中流出并最终脱气到大气中。解决这些问题需要来自太阳系探索和系外行星观测以及实验室实验的约束。