Exploring the spatial, temporal, and vertical distribution of methane in Pluto's atmosphere

•A study of temporal, rotational, and vertical variability of Pluto’s atmospheric methane is performed.•No variations of the methane column larger than 20% with Pluto’s phase are present.•At most marginal temporal variations over 2008–2012 are found.•Large departures from uniform mixing are excluded.•The source of methane gas is probably the large scale CH4 ice deposits, especially at high Northern latitudes.