Detection of H3+ on Jupiter

SINCE their detection in the high latitudes of Jupiter, first by the Voyager Ultraviolet Spectrometer (UVS) experiment 1,2 , then by the International Ultraviolet Explorer (IDE) satellite 3 , the auroral particle precipitations have been associated with various phenomena in the jovian environment. In the magnetosphere, the H + 3 ion, probably of ionospheric origin, was detected in situ by the Voyagers 4 . Infrared emissions were observed in spectral bands characteristic of CH 4 (ref. 5) and of other hydrocarbons 6,7 , localized in two auroral spots 5,8 . Here we present high-resolution spectra at a wavelength of 2 μm, in the southern auroral region of Jupiter, recorded at the Canada–France–Hawaii Telescope (CFHT), which we believe to be the first astronomical spectroscopic detection of H 3 + . The derived rotational temperature of H 3 + is in the range 1,000–1,200 K. Such strong H 3 + lines could be used in future ground-based monitoring of the jovian auroral activity and to search for this molecular ion in the interstellar medium.