Methane is a key species in the Outer Planets. It is the third most abundant molecule in all four Giant Planets, with a deep tropospheric abundance increasing from 0.2-0.4% (of the hydrogen-helium mix) at Jupiter and Saturn and about 2% in Uranus and Neptune. Its abundance is even larger in Titan, reaching 5% (of N2) at the surface. Related to its large abundance, methane plays a dominant role in governing the stratospheric chemistry of all the Outer Planets. In the thermal infrared, the methane 7.7 microns nu4 band has been widely observed. This band is more sensitive to temperature than to the methane abundance, however. On the other hand, weak pure rotational lines of methane at 50-250 microns are much more sensitive to the methane abundance. Therefore, the opening of the submillimeter range with Herschel represented an excellent opportunity for an improved determination of methane abundance and vertical profile in the Outer Planets. Observations of Neptune and Titan were performed in the winter 2011/2012 with the HIFI heterodyne submm instrument on board of the Herschel Space Observatory. The four main components of the CH4(J=6-5) rotational transition at 1882 GHz (i.e. 159.3 micron), were detected in emission. This represents the first times these lines are resolved spectrally (R 10^6). Moreover, observations of Uranus were performed in the same period, with the PACS spectrometer (R 1400) also on board of Herschel. A weak absorption of the CH4(J=6-5) transition was detected, but without resolving the four main component. These lines probe mainly the stratosphere of Neptune and Titan, and the tropopause of Uranus. We will present the methane abundance retrieved from these observations.< Leer menos