The melt productivity of a differentiated planet's mantle is primarily controlled by its iron content, which is itself approximated by the planet's core mass fraction (CMF). Here we show that estimates of an exoplanet's CMF allows robust predictions of the thickness, composition, and mineralogy of the derivative crust. These predicted crustal compositions allow constraints to be placed on volatile cycling between surface and the deep planetary interior, with implications for the evolution of habitable planetary surfaces. Planets with large, terrestrial-like CMFs (≥0.32) will exhibit thin crusts that are inefficient at transporting surface water and other volatiles into the underlying mantle. By contrast, rocky planets with smaller CMFs (≤0.24) and higher, Mars-like, mantle iron contents will develop thick crusts capable of stabilizing hydrous minerals, which can effectively sequester volatiles into planetary interiors and act to remove surface water over timescales relevant to evolution. The extent of core formation has profound consequences for the subsequent planetary surface environment and may provide additional constraints in the hunt for habitable, Earth-like exoplanets.

分化行星地幔的熔体生产力主要受其铁含量控制，而铁含量本身由行星的核心质量分数 (CMF) 近似。在这里，我们展示了对系外行星 CMF 的估计可以对衍生地壳的厚度、成分和矿物学进行可靠的预测。这些预测的地壳成分允许限制地表和深行星内部之间的挥发性循环，对宜居行星表面的演化产生影响。具有大型类地 CMF (≥0.32) 的行星将表现出薄壳，在将地表水和其他挥发物输送到下层地幔方面效率低下。相比之下，具有较小 CMF (≤0.24) 和更高的岩石行星，类似于火星，地幔铁含量将形成能够稳定含水矿物的厚壳，这可以有效地将挥发物隔离到行星内部，并在与进化相关的时间尺度内去除地表水。核心形成的程度对随后的行星表面环境产生深远的影响，并可能为寻找可居住的类地系外行星提供额外的限制。