Lammer Helmut, Schiefer Sonja-Charlotte, Juvan Ines, Odert Petra, Erkaev Nikolai V, Weber Christof, Kislyakova Kristina G, Güdel Manuel, Kirchengast Gottfried, Hanslmeier Arnold
Space Research Institute, Austrian Academy of Sciences, Graz, Austria,
Orig Life Evol Biosph. 2014 Sep;44(3):239-60. doi: 10.1007/s11084-014-9377-2. Epub 2014 Dec 17.
We study the origin and escape of catastrophically outgassed volatiles (H2O, CO2) from exomoons with Earth-like densities and masses of 0.1, 0.5 and 1 M⊕ orbiting an extra-solar gas giant inside the habitable zone of a young active solar-like star. We apply a radiation absorption and hydrodynamic upper atmosphere model to the three studied exomoon cases. We model the escape of hydrogen and dragged dissociation products O and C during the activity saturation phase of the young host star. Because the soft X-ray and EUV radiation of the young host star may be up to ~100 times higher compared to today's solar value during the first 100 Myr after the system's origin, an exomoon with a mass < 0.25 M⊕ located in the HZ may not be able to keep an atmosphere because of its low gravity. Depending on the spectral type and XUV activity evolution of the host star, exomoons with masses between ~0.25 and 0.5 M⊕ may evolve to Mars-like habitats. More massive bodies with masses >0.5 M⊕, however, may evolve to habitats that are a mixture of Mars-like and Earth-analogue habitats, so that life may originate and evolve at the exomoon's surface.
我们研究了具有类地密度且质量分别为0.1、0.5和1 M⊕的系外卫星灾难性释放挥发物（H2O、CO2）的起源和逃逸情况，这些系外卫星围绕一颗年轻活跃的类太阳恒星宜居区内的一颗太阳系外气态巨行星运行。我们将辐射吸收和流体动力学高层大气模型应用于三个研究的系外卫星案例。我们模拟了年轻主恒星活动饱和阶段氢气以及被拖拽的解离产物O和C的逃逸情况。由于年轻主恒星的软X射线和极紫外辐射在系统形成后的前10亿年里可能比现今太阳的值高出约100倍，因此位于宜居区内质量<0.25 M⊕的系外卫星可能因其低重力而无法保留大气层。根据主恒星的光谱类型和XUV活动演化情况，质量在~0.25至0.5 M⊕之间的系外卫星可能会演变成类似火星的栖息地。然而，质量>0.5 M⊕的更大质量天体可能会演变成类似火星和类似地球栖息地混合的环境，这样生命可能会在系外卫星表面起源和演化。
