Hot CH4 in the polar regions of Jupiter.

We have obtained 3.3–3.4-μm spectro-images of Jupiter including CH 4 and H 3 + emission lines from both polar regions at the Gemini North telescope. We find that the peak of the 3-μm CH 4 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 H 3 + bright spot. We derive high temperatures (500–850 K) from CH 4 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 CH 4 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. [ABSTRACT FROM AUTHOR]