Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact strongly with the surface, such as neon (detected on the Moon) and helium (detected both on the Moon and at Mercury), but also argon, a noble gas (detected on the Moon) that surprisingly adsorbs at the cold lunar nighttime surface. Refractories include species such as calcium, magnesium, iron, and aluminum, all of which have very strong bonds with the lunar surface and thus need energetic processes to be ejected into the exosphere. Here we focus on the properties of species that have been detected in the exospheres of inner Solar System bodies, specifically the Moon and Mercury, and how they provide important information to understand source and loss processes of these exospheres, as well as their dependence on variations in external drivers.

挥发物和难熔物代表任何表面边界外逸层中物种挥发性范围的两个端部成员。挥发物包括与表面不发生强烈相互作用的元素，例如氖（在月球上检测到）和氦（在月球和水星上均检测到），还有氩，一种惰性气体（在月球上检测到），它具有惊人的吸附性在寒冷的月球夜间表面。耐火材料包括钙、镁、铁和铝等物质，所有这些物质与月球表面都有很强的结合力，因此需要高能过程才能喷射到外逸层。在这里，我们重点关注在太阳系内部天体（特别是月球和水星）的外逸层中检测到的物种的特性，以及它们如何提供重要信息来了解这些外逸层的来源和损失过程，以及它们对变化的依赖性在外部驱动程序中。