Methane is one of the simplest stable molecules that is both abundant and widely distributed across space. Observational surveys of CH₄ ice towards low- and high-mass young stellar objects showed that much of the CH₄ is expected to be formed by the hydrogenation of C on dust grains, and that CH₄ ice is strongly correlated with solid H₂O. However, this has not been investigated under controlled laboratory conditions. Here, we successfully demonstrate with a C-atom beam implemented in an ultrahigh vacuum apparatus the formation of CH₄ ice in two separate co-deposition experiments: C + H on a 10 K surface to mimic CH₄ formation directly before H₂O ice is formed on the dust grain, and C + H + H₂O on a 10 K surface to mimic CH₄ formed simultaneously with H₂O ice. We confirm that CH₄ can be formed by the reaction of atomic C and H, and that the CH₄ formation rate is twice as high when CH₄ is formed within a H₂O-rich ice. This is in agreement with the observational finding that interstellar CH₄ and H₂O form together in the polar ice phase. The conditions that lead to interstellar CH₄ (and CD₄) ice formation are reported, and can be incorporated into astrochemical models to further constrain CH₄ chemistry in the interstellar medium and in other regions where CH₄ is inherited.

甲烷是最简单的稳定分子之一，它既丰富又广泛分布在整个太空中。对低质量和高质量年轻恒星物体的CH ₄冰的观测研究表明，预计大部分CH ₄是由尘埃颗粒上C的氢化形成的，并且CH ₄冰与固体H ₂ O密切相关。但是，尚未在受控的实验室条件下对此进行调查。在这里，我们成功地用超高真空装置中的C原子束证明了CH ₄冰的形成是通过两个单独的共沉积实验：在10 K表面上的C + H模仿H ₂之前的CH ₄形成O冰在尘埃颗粒上形成，C + H + H ₂ O在10 K表面上形成，以模仿与H ₂ O冰同时形成的CH ₄。我们证实，CH ₄可以通过原子C与H的反应形成，并且当CH ₄在富含H ₂ O的冰中形成时，CH _4的形成速率是其两倍。这与观测结果一致，即星际CH ₄和H ₂ O在极地冰期一起形成。据报道导致星际CH ₄（和CD ₄）冰形成的条件，可以将其纳入天化学模型以进一步约束CH在星际介质和继承CH _4的其他区域有_4种化学物质。