The Atmosphere Structure Instrument on the Galileo probe detected wave
like temperature fluctuations superimposed on a 700-kelvin temperature
increase in Jupiter's thermosphere. These fluctuations are consistent
with gravity waves that are viscously damped in the thermosphere. Mor
eover, heating by these waves can explain the temperature increase mea
sured by the probe, This heating mechanism should be applicable to the
thermospheres of the other giant planets and may help solve the long-
standing question of the source of their high thermospheric temperatur
es.