Hot CH4 in the polar regions of Jupiter

We have obtained 3.3-3.4-μm spectro-images of Jupiter including CH4 and H3+ emission lines from both polar regions at the Gemini North telescope. We find that the peak of the 3-μm CH4 northern bright spot is located at ∼200° (SysIII) longitude, ∼20° west of the center of the 8-μm north-polar bright spot, and does not coincide with the 3-μm H3+ bright spot. We derive high temperatures (500-850 K) from CH4 rotational lines on the bright spots of both polar regions, above the 1-μbar pressure level, while we find cooler temperatures (<350 K) over the 8-μm spot. The intensity ratios of the various 3-μm vibrational bands of CH4 are roughly constant, indicating that the upper states of these bands are mostly populated by non-thermal excitation mechanisms, such as auroral particle precipitation and/or Joule heating, in contrast with the 8-μm thermal emission.