艾琳球内部：系外行星可水层与宜居层中孔隙度、热通量与矿物学的相互作用
Inside the Eirenesphere: The Interplay of Porosity, Heat Flux and Mineralogy in Exoplanetary Aquable and Habitable Layers
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中文总结 AI 辅助
该研究提出整合孔隙度、热通量与矿物学的地球物理模型，量化系外行星次表层宜居体积（艾琳球），发现成熟超级地球宜居性最优，且次表层生命可延伸至5-7天文单位，将宜居性视为行星固有属性。
中文摘要 AI 辅助
经典环恒星宜居带将生命搜寻限制在恒星辐照维持液态水的行星表面，忽视了广阔的次表层环境。在此，我们提出一个整合内部径向结构、矿物学、放射性生热和随压力变化的孔隙度的地球物理模型，以量化岩石质系外行星的三维宜居体积——艾琳球。我们区分了可水性（热力学水的稳定性）与宜居性，后者要求温度和压力处于极端微生物生物学极限之内，并需足够的孔隙度以供流体循环。为比较行星容量，我们引入艾琳球体积指数（EVI），衡量平均次表层生物圈体积。应用此框架，我们发现地球当前状态（EVI约为0.06个地球海洋体积）仅代表中等水平。相反，具有高地质活动的成熟超级地球为深层生物圈提供了最广阔的环境。地壳矿物学起到一阶控制作用：热绝缘的长英质地壳维持的艾琳球显著大于原生镁铁质岩性。追踪长期冷却揭示内部宜居性是一种演化属性；年轻行星因陡峭的热梯度而拥有受限的生物圈，而成熟世界则在数十亿年间最大化宜居体积。最后，我们证明在类太阳恒星周围，次表层宜居性可延伸至5-7天文单位，有效将生命潜力与表面辐射平衡解耦。外推至银河系，揭示出惊人的银河系次表层生命容量，约为数十亿个地球海洋体积。最终，此框架将天体生物学范式从依赖表面的现象转变为行星固有属性，提供了用于优先排序目标的度量标准。
英文摘要
The classical circumstellar habitable zone restricts the search for life to planetary surfaces where stellar irradiation sustains liquid water, overlooking vast subsurface environments. Here, we present a geophysical model integrating internal radial structure, mineralogy, radiogenic heat, and pressure-dependent porosity to quantify the three-dimensional habitable volume-the eirenesphere-of rocky exoplanets. We distinguish between aquability (thermodynamic water stability) and habitability, which requires temperatures and pressures within extremophile biological limits, plus sufficient porosity for fluid circulation. To compare planetary capacities, we introduce the Eirenesphere Volumetric Index (EVI), measuring average subsurface biosphere volume. Applying this framework, we find that Earth's current state (EVI$\approx 0.06$ terrestrial oceans) represents only a moderate regime. Instead, mature super-Earths with high geothermal activity provide the most extensive environments for deep biospheres. Crustal mineralogy exerts a first-order control: thermally insulating felsic crusts sustain significantly larger eirenespheres than primary mafic lithologies. Tracking secular cooling reveals internal habitability is an evolutionary property; young planets host confined biospheres due to steep thermal gradients, whereas mature worlds maximize habitable volumes over billions of years. Finally, we demonstrate that around solar-like stars, subsurface habitability persists out to $5-7$ au, effectively decoupling life's potential from surface radiative balance. Extrapolating to the Milky Way reveals a staggering galactic capacity for subsurface life, on the order of billions of terrestrial oceans. Ultimately, this framework shifts the astrobiological paradigm from a surface-dependent phenomenon to an intrinsic planetary property, offering a metric to prioritize targets.
发表机构
- Universidad de Antioquia（安第斯大学）
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