  We present suggestive evidence for an inverse energy cascade within Jupiter's
atmosphere through a calculation of the power spectrum of its kinetic energy
and its cloud patterns. Using Cassini observations, we composed
full-longitudinal mosaics of Jupiter's atmosphere at several wavelengths. We
also utilized image pairs derived from these observations to generate
full-longitudinal maps of wind vectors and atmospheric kinetic energy within
Jupiter's troposphere. We computed power spectra of the image mosaics and
kinetic energy maps using spherical harmonic analysis. Power spectra of
Jupiter's cloud patterns imaged at certain wavelengths resemble theoretical
spectra of two-dimensional turbulence, with power-law slopes near -5/3 and -3
at low and high wavenumbers, respectively. The slopes of the kinetic energy
power spectrum are also near -5/3 at low wavenumbers. At high wavenumbers,
however, the spectral slopes are relatively flatter than the theoretical
prediction of -3. Our results also show the importance of calculating spectral
slopes from full 2D velocity maps rather than 1D zonal mean velocity profiles,
since at large wavenumbers the spectra differ significantly, though at low
wavenumbers, the 1D zonal and full 2D kinetic energy spectra are practically
indistinguishable. Furthermore, the difference between the image and kinetic
energy spectra suggests some caution in the interpretation of power spectrum
results solely from image mosaics and its significance for the underlying
dynamics. Finally, we also report prominent variations in kinetic energy within
the equatorial jet stream that appear to be associated with the 5 {\mu}m
hotspots. Other eddies are present within the flow collar of the Great Red
Spot, suggesting caution when interpreting snapshots of the flow inside these
features as representative of a time-averaged state.
