Kuiper belt objects (KBOs) have diverse surface compositions, and the New Horizons mission to the Pluto-Charon system allows us to test hypotheses on the origin and evolution of these KBO surfaces. Previous work proposed that Charon’s organic-rich north pole formed from radiolytically processed volatiles sourced from Pluto’s escaping atmosphere. Here, we show an endogenic source of volatiles from Charon’s interior is plausible. We calculate that cryovolcanic resurfacing released 1.29 × 10¹⁵–3.47 × 10¹⁵ kg of methane to Charon’s surface from its interior. We modeled volatile transport and found the vast majority of this volcanically released methane migrates to Charon’s poles, with deposition rates sufficient to be processed into the observed organic compounds. Irradiated methane products appear on similarly sized KBOs that do not orbit a Pluto-sized object to draw an escaping atmosphere from, so interior-sourced volatiles could be a common and important process across the Kuiper belt.

柯伊伯带天体 (KBO) 具有不同的表面成分，新视野号前往冥王星-卡戎系统的任务使我们能够检验有关这些 KBO 表面的起源和演化的假设。之前的研究提出，卡戎富含有机物的北极是由来自冥王星逃逸大气的辐射分解处理的挥发物形成的。在这里，我们证明卡戎内部挥发物的内源性来源是合理的。我们计算出，低温火山表面重修从卡戎内部向卡戎表面释放了 1.29 × 10 ¹⁵ –3.47 × 10 ¹⁵千克甲烷。我们对挥发性迁移进行了建模，发现绝大多数火山释放的甲烷迁移到卡戎的两极，其沉积速率足以加工成观察到的有机化合物。受辐照的甲烷产物出现在类似大小的柯伊伯带天体上，这些柯伊伯带天体不围绕冥王星大小的物体运行以从中吸取逸出的大气，因此内部来源的挥发物可能是整个柯伊伯带的常见且重要的过程。