For rocky exoplanets, knowledge of their geologic characteristics such as composition and mineralogy, surface recycling mechanisms, and volcanic behavior are key to determining their suitability to host life. Thus, determining exoplanet habitability requires an understanding of surface chemistry, and understanding the composition of exoplanet surfaces necessitates applying methods from the field of igneous petrology. Piston-cylinder partial melting experiments were conducted on two hypothetical rocky exoplanet bulk silicate compositions. HEX1, a composition with molar Mg/Si = 1.42 (higher than bulk silicate Earth's Mg/Si = 1.23) yields a solidus similar to that of Earth's undepleted mantle. However, HEX2, a composition with molar Ca/Al = 1.07 (higher than Earth Ca/Al = 0.72) has a solidus with a slope of ∼10°C/kbar (vs. ∼15°C/kbar for Earth) and as result, has much lower melting temperatures than Earth. The majority of predicted adiabats point toward the likely formation of a silicate magma ocean for exoplanets with a mantle composition similar to HEX2. For adiabats that do intersect HEX2's solidus, decompression melting initiates at pressures more than 4x greater than in the modern Earth's undepleted mantle. The experimental partial melt compositions for these exoplanet mantle analogs are broadly similar to primitive terrestrial magmas but with higher CaO, and for the HEX2 composition, higher SiO₂ for a given degree of melting. This first of its kind exoplanetary experimental data can be used to calibrate future exoplanet petrologic models and predict volatile solubilities, volcanic degassing, and crust compositions for exoplanets with bulk compositions and ƒO₂ similar to those explored herein.

中文翻译：

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两种可能的岩石系外行星成分的地幔固体成分和熔体成分的实验测定

对于岩石系外行星，了解它们的地质特征（如成分和矿物学、表面再循环机制和火山行为）是确定它们是否适合承载生命的关键。因此，确定系外行星的宜居性需要了解表面化学，而了解系外行星表面的组成需要应用火成岩学领域的方法。在两个假设的岩石系外行星块状硅酸盐组合物上进行了活塞-圆柱体部分熔化实验。HEX1，摩尔 Mg/Si = 1.42（高于块状硅酸盐地球的 Mg/Si = 1.23）的组成产生类似于地球未耗尽地幔的固相线。然而，HEX2 是一种摩尔 Ca/Al = 1.07（高于地球 Ca/Al = 0.72）的成分，其固相线斜率为 ~10°C/kbar（vs. 约 15°C/kbar（地球），因此其熔化温度比地球低得多。大多数预测的绝热体都指向地幔成分类似于 HEX2 的系外行星可能形成硅酸盐岩浆海洋。对于确实与 HEX2 的固相线相交的绝热体，减压熔化在比现代地球未耗尽地幔高 4 倍的压力下开始。这些系外行星地幔类似物的实验部分熔融成分与原始地球岩浆大致相似，但具有较高的 CaO，对于 HEX2 成分，较高的 SiO 在固相线中，减压熔化开始的压力是现代地球未耗尽地幔的 4 倍以上。这些系外行星地幔类似物的实验部分熔融成分与原始地球岩浆大致相似，但具有较高的 CaO，对于 HEX2 成分，较高的 SiO 在固相线中，减压熔化开始的压力是现代地球未耗尽地幔的 4 倍以上。这些系外行星地幔类似物的实验部分熔融成分与原始地球岩浆大致相似，但具有较高的 CaO，对于 HEX2 成分，较高的 SiO₂对于给定的熔化程度。这首个此类系外行星实验数据可用于校准未来的系外行星岩石学模型，并预测具有大量成分和 ƒO _{2 的系}外行星的挥发性溶解度、火山脱气和地壳成分，类似于本文所探索的那些。