Limb images of the low latitude UV O2 Herzberg I emission were obtained from a low Earth orbit spacecraft in early 1988. The layer displays patchy, sometimes horizontally periodic, spatial variability on scales of tens of km with amplitude up to 20%. We interpret periodic wavelike features in terms of perturbations associated with gravity wave propagation through the layer. The putative waves are shown to have horizontal wavelength about 15 km, similar vertical wavelength, and temperature oscillation roughly equal to or exceeding the observed emission perturbation. ¿ American Geophysical Union 1992