NASA's New Horizons data revealed a geologically complex past on Charon. Here, we show cryovolcanic eruptions released enough methane to source Charon's red polar cap. We observe methane and their products on other Kuiper belt objects, so this process could be important across the Kuiper belt.

We developed a protocol that may be used to monitor and minimise the microbiological contamination of planetary field analogues of icy moons in their analysis. It may serve as a test-bed for procedures of decontamination of samples from future landing/return missions to icy moons.