Gravity waves in Titan’s lower stratosphere from Huygens probe in situ temperature measurements

• First discovery of gravity waves in lower stratosphere (60–140 km).
• Wavelength of 3–8 km and peak–peak of 2–3 K.
• Physical response of different sensors gives robust detection.
• Consistent with amplitude vs. height of other Titan gravity waves.

The Huygens probe recorded atmospheric temperatures during its parachute descent through the atmosphere of Titan. A careful analysis of these data reveals for the first time spectacular but hitherto-unreported small-scale variations in stratospheric temperatures that we interpret as gravity waves, consistent with detection of such waves at higher altitudes by other means. The structures have a vertical wavelength of 3–8 km and a peak–peak amplitude of ∼2 K that is roughly constant over altitudes from ∼140 km, where measurements began, to ∼60 km. This altitude, below which no significant temperature waves are seen, coincides with a local maximum in the zonal wind profile, and is close to where the Brunt–Väisälä frequency is highest. It seems possible that the zonal wind field influences the vertical gravity wave propagation.