Black: Pluto spectrum at 2330–2342 and 2345–2356 nm (arbitrary units). The total integration time is 7h20 min. The spectral resolution is 60 000. Red, blue and green curves show synthetic spectra for an isothermal Pluto atmosphere at T = 90 K, and including telluric and solar lines. Green: no methane and CO in Pluto’s atmosphere. Blue: methane is included with a 0.75 cm-am column density. Red: CO is also included with a column density of 0.07 cm-am. Blue dots locate the methane features that were used in the line coaddition process shown in Fig. 2.