Space-Time Relationships in the UV Markings on Venus

Abstract

Specially prepared sections of pictures taken with the Mariner 10 television cameras are composited to show the time development of UV markings at various locations on Venus. A second series of composite pictures shows the development of selected UV markings in a frame of reference which follows the apparent zonal motion. BY comparing these composites with individual TV pictures, we show that large-scale markings (?1000 km) between ±45° latitude have lifetimes exceeding 4 days and move en masse with the apparent angular motion at the equator. Smaller scale markings (100?500 km) are found to have lifetimes in excess of 1.5 days but less than 4 days. The polar ring, bow-like waves, circumequatorial belts and cellular features all show rapid growth, modulation or propagation characteristics in the pictures. The long lifetime of large-scale markings permits us to interpret the time development pictures as spatial maps of the entire face of Venus at the time of Mariner 10 encounter. A single, dark, horizontal Y is found to encircle the planet. At high southerly latitudes (>40°) the large-scale pattern of markings is found to he decoupled from the mean flow as defined by small-scale markings. This is also the case for the polar ring which also shows noticeable diurnal changes. These observations suggest that the Y and the polar ring are both visible manifestations of propagating waves.