Long-wavelength density fluctuations resolved in Pluto's high atmosphere

Near-infrared measurements of the occultation of star P445.3 by Pluto on 2007 March 18 reveal that Pluto's upper atmosphere (200-400 km altitude) is unexpectedly dynamic. At a wavelength of 1.6 μm, numerous vertical fluctuations (8-20 km) of density are detected with unprecedented signal-to-noise ratio. These fluctuations are achromatic, nearly limb-aligned, and fully resolved along a 1000 km path over a pressure range of 0.1-0.7 μbar (0.01 to 0.07 Pa). Vertical wavelength increases with altitude indicating a high-frequency cutoff operating on a broad-band spectrum of buoyancy ("gravity") waves generated deeper in Pluto's atmosphere.