Hot CH4 in the polar regions of Jupiter

We have obtained 33-3.4-mu m spectro-images of Jupiter including CH4 and H-3(+); emission lines from both polar regions at the Gemini North telescope. We find that the peak of the 3-mu m CH4 northern bright spot is located at similar to 200 degrees (SysIll) longitude, similar to 20 degrees west of the center of the 8-mu m north-polar bright spot, and does not coincide with the 3-mu m H-3(+) bright spot. We derive high temperatures (500-850 K) from CH4 rotational lines on the bright spots of both polar regions, above the 1-mu bar pressure level, while we find cooler temperatures (<350 K) over the 8-mu m spot. The intensity ratios of the various 3-mu m 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-mu m thermal emission. (C) 2015 Elsevier Inc. All rights reserved.