近日，美国亚利桑那州立大学Shim, S.-H.团队报道了通过高压岩浆氢反应形成含水行星。2025年10月29日出版的《自然》杂志发表了这项成果。

近轨道运行的亚海王星在银河系中普遍存在。根据其观测到的半径-质量关系所建立的行星内部模型表明，这类行星外部包裹着相当比例的氢气（干行星）或水（湿行星），其内核则由岩石和金属构成。学界曾认为富水亚海王星形成于距离恒星更远的区域，随后迁移至当前轨道。

研究组通过实验证实，在高压环境下，温暖稠密的氢流体与硅酸盐熔体发生反应，促使岩浆中的硅析出形成合金和氢化物。他们发现，从硅酸盐熔体中释放的氧会与氢反应，生成高达数十重量百分比的水——这一比例远高于基于低压理想气体模型所做的预测。这些反应能够在富氢行星中形成一系列不同含水量的天体，部分亚海王星甚至可能达到富水组成，这暗示着富氢行星与富水行星之间可能存在演化关联。由此看来，在系外行星大气中探测到大量水分，或许不能作为行星在原行星盘内发生轨道迁移的决定性证据，这对传统认为的行星组成与形成位置之间的关联提出了挑战。

附：英文原文

Title: Building wet planets through high-pressure magma–hydrogen reactions

Author: Horn, H. W., Vazan, A., Chariton, S., Prakapenka, V. B., Shim, S.-H.

Issue&Volume: 2025-10-29

Abstract: Close-in transiting sub-Neptunes are abundant in our Galaxy1. Planetary interior models based on their observed radius–mass relationship suggest that sub-Neptunes contain a discernible amount of either hydrogen (dry planets) or water (wet planets) blanketing a core composed of rocks and metal2. Water-rich sub-Neptunes have been believed to form farther from the star and then migrate inwards to their present orbits3. Here we report experimental evidence of reactions between warm, dense hydrogen fluid and silicate melt that release silicon from the magma to form alloys and hydrides at high pressures. We found that oxygen liberated from the silicate melt reacts with hydrogen, producing an appreciable amount of water up to a few tens of weight per cent, which is much greater than previously predicted based on low-pressure ideal gas extrapolation4,5. Consequently, these reactions can generate a spectrum of water contents in hydrogen-rich planets, with the potential to reach water-rich compositions for some sub-Neptunes, implying an evolutionary relationship between hydrogen-rich and water-rich planets. Therefore, detection of a large amount of water in exoplanet atmospheres may not be the optimal evidence for planet migration in the protoplanetary disk, calling into question the assumed link between composition and planet formation location.

DOI: 10.1038/s41586-025-09630-7

Source: https://www.nature.com/articles/s41586-025-09630-7