M.J.S. Belton, P.J. Gierasch, M.D. Smith, P. Helfenstein, P.J. Schinder, J.B. Pollack, K.A. Rages, A.P. Ingersoll, K.P. Klaasen, J. Veverka, C.D. Anger, M.H. Carr, C.R. Chapman, M.E. Davies, F.P. Fanale, R. Greeley, R. Greenberg, J. W. Head III, D. Morrison, G. Neukum, C.B. Pilcher
Images of Venus taken at 418 (violet) and 986 [near-infrared (NIR)] nanometers show that the morphology and motions of large-scale features change with depth in the cloud deck. Poleward meridional velocities, seen in both spectral regions, are much reduced in the NIR. In the south polar region the markings in the two wavelength bands are strongly anticorrelated. The images follow the changing state of the upper cloud layer downwind of the subsolar point, and the zonal flow field shows a longitudinal periodicity that may be coupled to the formation of large-scale planetary waves. No optical lightning was detected.